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FREE RADICALS IN THE PHOTOLYSIS OF PROPIONALDEHYDE

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Xerox University Microfilms
300 North Z e e b Ro a d
Ann Arbor, M ichigan 4S106
LD3907
.07
Hay, L e o n a r d .
1J
1u ;
1941
Free r a d ic a ls in th e p h o to ly s is of
.1-138
p ro p io n a ld e h y ae ...
New Y o r k , 1 9 4 1 .
4 p ,l,,4 3 typew ritten leaves.
tables,
diagrs.
29cm.
T h e s i s ( P h . D . ) - New Y o r k u n i v e r s i t y ,
G rad u ate s c h o o l, 1941.
B ibliography: p . 39-40.
A G7 9 2 7
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T H I S D I S S E R T A T I O N HAS BEEN M I C R O F I L M E D E X A C T L Y AS R E C E I V E D .
N . Y, U n i v .’
FREE RADICALS IN THE PHOTOLYSIS OF PROPIONALDEHYDE
A Thesis
Subm itted
in P a r t i a l
Requirem ents
F u lfillm e n t of
for
D octor of
the
Degree
Philosophy
at
New Y o r k U n i v e r s i t y
toy
L e o n a r d May
March,
1941
of
the
ACKNOWLEDGEMENT
The w r i t e r w i s h e s ,
at
thank Dr.
H. A u s t i n T a y l o r
for
con stan t advice
in
their
the
course
of
this
this
tim e,
and Dr.
and
to
M ilton
inspiration
research.
Burton
J
TABLE OF CONTENTS
Page
I n t r o d u c t i o n ..................................................................................................... . . I
Experim ental P a rt
A.
D escription
B.
P urification
C* M i r r o r
o f A p p a r a t u s ................................................ , 1 0
o f M a t e r i a l s .............................. . .............. 12
t e c h n i q u e ........................................................................ 14
D. D e t e c t i o n
o f A l k y l R a d i c a l s * . ..................... . . . . . . 1 8
E.
Test3
F.
D eterm in atio n s of H alf-L iv es of
F r e e R a d i c a l s ........................................................ . . 2 3
Li. T e s t
f o r H y d r o g e n A t o m s ............................................... * 2 0
f o r P h o t o s e n s i t i z a t i o n . . . .................................. 27
D i s c u s s i o n .......................................................................................................... , 2 9
S u m m a r y ................................................................................................................. . . 3 7
B i b l i o g r a p h y ............................................................................................. . . . . 3 9
Appendix
41
L IS T OF TABLES
No*
I.
II.
III.
T itle
A fter
Acid C o n te n t o f Samples o f
P r o p i o n a l d e h y d e . . . ................................
13
C a l c u l a t i o n o f Maximum H y d r o g e n At om
p r o d u c t i o n from G uard M i r r o r D a t a . . .
El
T abulations
of Data;
A- Sample C a l c u l a t i o n s
and T a b l e s I I I B and
for Fig. 4 & 6
I I I C ...........................
24
B. F r e e R a d i c a l C o n c e n t r a t i o n s i n
P h o t o l y s i s o f P r o p i o n a l d e h y d e ..............
25
C.
Free R ad ical C o n cen tratio n s in
p h o t o l y s i s o f A c e t o n e ......................
26
page
L I S T OF ILLUSTRATIONS
No.
T itle
1.
Diagram
2.
Rate
3.
of A pparatus
A fter
..
10
o f flo w of v a p o rs th ro u g h
q u a r t z t u b e .....................................................
10
Time o f a n t i m o n y m i r r o r r e m o v a l i n
p h o to ly sis of propionaldehyde..
24
4 . (a. a n d b ) d i s a p p e a r a n c e o f f r e e r a d i c a l s
in p h o t o l y s i s of p r o p io n a ld e h y d e ..
5..
b»(a,b)
7*
8
*.
25
Time o f a n t i m o n y m i r r o r r e m o v a l
in
p h o t o l y s i s o f a c e t o n e .............................
26
D i s a p p e a r a n c e of f r e e r a d i c a l s
i n p h o t o l y s i s o f a c e t o n e ..........................
26
Comparison of the r a t e s of d i s ­
ap pearance of a lk y l r a d i c a l s in
the p h o t o l y s i s of p ro p io n a ld e h y d e
a n d p h o t o l y s i s o f a c e t o n e ...................
27
D isap p earan ce of m ethyl r a d i c a l s
- - f r o m P a n e t h , H o f e d i t z , and Wunsch,
J . C h e m . S o c , , ( 1 9 3 5 ) , 3 7 2 .......................
42
page
INTRODUCTION
From t h e v i e w p o i n t
in
a photochem ical
such research
particularly
can
bring
been o b ta in e d
question,
turn,
into
of
the
the
light
of
vast m ajority
either
split
wa s p a r t
that
rearrange
off
free
reaction..
in
all
interest
in f o r m a t io n any
do n o t
in
general,
involve
is,
other
varies
as
s o me p o w e r
of
the prim ary
is
to
determ ine
them selves
act.
excitation,
the deco m p o sitio n
is
fundam entally
individual
product m olecules,
m olecules
or
they
capable
of u n d erg o in g
hand,
the
overall
rate
than
the
first:
concentration
a reaction,
task
the
of
that
of
is,
the
the rate
reactant,
any t h e o r y to e x p l a i n ,
case
of
the
o rd er with p re s s u re ,
and any g r e a t e x c e s s
in
the
actual
which c a n n o t
of
the
sim ple c o l l i s i o n
rate
further
of r e a c t i o n
the
Two m a i n t h e o r i e s
r e s u l t had
which a re
the
prevailing
order,
any change
or deficiency
be e x p l a i n e d
by means
theory.
are
-
available
1-
a
This
or rearran g e
in
reaction
solve
undergoing decom position
compounds
into
of the
It
problem:
excitation
themselves
to
the
propionaldehyde.
compounds
after
a higher order
one.
therm al chem istry:
of organic
of
than
chief
which no c o n c l u s i v e
modern t h e o r i e s ,
ma y b e
greater
the
the
present research
of a l a r g e r
after
radicals
On t h e
the
of
organic
m olecules
unim olecular:
in
methods
radicals
ultim ate
In
in
operations
decom position of
in g e n e r a l,
free
perhaps
on c h e m i c a l p r o c e s s e s
mechanism i n
by t h e
the
produce
bear
was a p p l i e d
mechanism o f
whether,
to
lies
most chem ical
in r e a c t i o n
in
chem ist,
techniques.
Photolysis
problem
the
investigation
since
photochem ical
of
to d ay to a c c o u n t
for
the
great
body o f
inform ation
decom position
which has
of organic
compounds.
Lindemann^, m o d if ie d by R ic e
4
and K assel •
The e s s e n c e o f
there
is
a time
decom position;
(collision)
ecular
the
process
general,
pressures
roughly
in
of
appearance
specific
in
the
it
of
may b e
buted
said
in
only
that
the
to
the
as
or
in
can
the
overall
since
rate,
at
of
rates
of a ctiv ate d
low p r e s s u r e s .
the
the
probability
broken in
the
between
our p u rposes,
idea:
that
abnorm­
o r d e r n e e d be a t t r i ­
of a c tiv a tio n ,
m olecules
reaction
or a larger
is
but for
and
find,
a t high
the d i f f e r e n c e s
rate
of
and K a s s e l4 proposed
bond w h ic h
of
slow er
we s h o u l d
reaction
embody one c e n t r a l
the r e l a t i v e
and c o n v e r s i o n
the
prevails
functions
the
reaction
its
a uniraol-
they ex p lain ed
be e x t e n s i v e ,
they
and
(1)
of a c t i v a t i o n
energy of a c t i v a t i o n ,
The d i s c u s s i o n
m odifications
alities
(4)
reaction
in which
instances,
molecule
decom position.
these
and
a second-order
m odifications
rates,
energy,
rate
and Ram sperger2 , H inshelw ood3,
successive
the
the
that
w ith d im in ish in g p ressu re
controls
a first-order
is
a bim olecular
decom position
that
quickly
processes
that
and
Rice
(3)
of d e c o m p o s it io n ; ,
t wo c o n s e c u t i v e
in
actual
is
of
Hinshelwood®,
o f a molecule
excitation
on t h e
that
the Lindemann th e o ry
process;
more
is
and R am sp erg er^,
the
and the
decreases
rate
The f i r s t
between e x c i t a t i o n
(2 ) t h a t
(adiabatic)
therefore
than
lag
been accum ulated
into
deactivation,
th e ir ultim ate
products.
The
to have
the
is
second
more
theory,
general
prim ary step,
the
form ation
in
that
of Rice
applicability.
a large
of f r e e
class
radicals
and H e r z f e l d ^ ,
This
theory
of o rg a n ic
appears
states
(a)
that
decom positions,
im m ediately a f t e r a c t i v a t i o n ;
(b)
that
cause
in
these
a reaction
collisions
about
(c)
free
radicals
of normal
requiring
overall
order
of
chain-ending
step,
over
Although,
lies
had
in
little
finding
radicals
different
case
can
a am all
the
before
any
decom positions
free
rate,
fa s t reactions
t h a t , the
radicals
in
1929,
methods,
large
group
at
least
direct
for
the
via
radical
H erzfeld
theory,
to
the
Rice
and R am sp e rg e r,
propionaldehyde
cation
of
It
radical
tional
is
is
not
to
order
reaction
of
an
bring
chains,
by
aliphatic
and
the
the
free
difficu lty
been p r e s e n t e d
•
There
free
of which
in
a
a
From a t h e o r e t i c a l
should
decom position.
exception
direct
free
all
that
several
radicals
acetaldehyde,
its
are
by means
used data
excellent
to
methods
radicals,
proceed
Yet i t
the
R ice-
of detection
b u t Hinshelwood,
on t h e
quantitative
strange
that
of
the
pyrolysis
v erifi­
be d i s p u t e d .
transition
from
(form aldehyde)
(propionaldehyde
application
normal r a t e
im portant proving
a gradual
to
theories.
should
second-order p yro ly sis
of
did
reactions
order
constitute
there
secure
7
below.
in
energy,
gaseous unim olecular
indirect,
and K a s s e l
to
therefore
reaction
absenoe
respective
mechanisms
aldehydes
group
their
only
of
has n o t
like
to
conditions*
today
a tantalizing
for not
seem
of
given
mechanism
constitute
indicate
of
presence
propionaldehyde,
to
are
of
some p a r t
and
once
w ith o th e r m olecules
reaction
concept
s t a n d i n g * 3,
view point,
appeared
range
the
at
ma y b e d e t e r m i n e d
o r no
Examples
free
react
w ith long
a wide
combine
activation
which evidence
play
be ma d e
or
reaction
reaction*
a
ma y e i t h e r
to
The
blit o f
lower
gound,
for
of
free
frac­
aliphatic
in
this
a characteristic
a com posite
or chloral)® .
m ultiple-
The c o n f l i c t
between
of
the
case:
the
two
prim ary
w hether
theories
step
this
can
after
be
settled
activation
prim ary
step
is
is
the
o n l y when th e
nature
determ ined
each
production
in
of u ltim a te
m olecules
RHCO
or
the
splitting
further
of
RH t CO
free
radicals
capable
of
taking p a rt
in
reactions:
RHCC
Methods
»
involving
R * HCO.
analysis
of
the
products
of decom position*
* B e r t h e l o t and Gaudechon (Ccmptes R endus, 151, 478, (1 9 1 0 ) )
f o u n d 2 0 % o f b u t a n e among t h e p r o d u c t s o f t h e p r o l o n g e d s t a t i c
p h o t o l y s i s o f Et CH O , t h e r e s t b e i n g l a r g e l y CO 4 H g .
Leighton
a n d B l a c e t ( J . A . C . S . ^54, 3 1 6 5 , ( 1 9 3 2 ) ) f o u n d 3 0me h y d r o g e n
a n d b u t a n e among t h e p r o d u c t s o f s u c h a p h o t o l y s i s , b u t f a r
more e t h a n e t h a n b u t a n e , and c o n c l u d e d t h a t a p p r o x i m a t e l y 80^
o f t h e m o l e c u l e s p r o c e e d e d t o t h e u l t i m a t e p r o d u c t s ( Cg Hg * CO)
in the p rim ary s t e p , w h ile the r e s t produced e t h y l r a d i c a l s
and e v e n tu a lly b u ta n e,
in the p y r o l y s is of p ro p io n a ld e h y d e,
H in s h e lw o o d and Thompson (P ro c ^ R o y . S o c . (London) 113A.S S 2 ,
(1926)) f o u n d n o b u t a n e , b u t o n l y e t h a n e a n d m e t h a n e Tn
t h e r a n g e 506°-604°c., e t h a n e p r e d o m i n a t i n g a t l o w e r t e m p e r ­
a t u r e s and m ethane a t h i g h e r ; t r a c e s o f e t h y l e n e were a l s o
present.
W in k le r , F l e t c h e r , and H in s h e lw o o d ( P r o c . Roy. Soc.
( L o n d o n ) , 146A. 345, (1934)) p e r f o r m e d t h e t h e r m a l d e c o m ­
p o s i t i o n i n t h e p r e s e n c e o f h y d r o g e n a t 549°C. w i t h v a r y i n g
in itia l pressures.
H y d r o g e n was u s e d t o m a i n t a i n t h e r a t e o f
a c t i v a t i o n f o r a u n i m o l e c u l a r r e a c t i o n d own t o l o w p r e s s u r e s .
A t 2 0 0 mm. , t h e p e r c e n t a g e s o f e t h a n e a n d u n s a t u r a t e s w e r e
2 4 * 3 a n d 8 . 5 r e s p e c t i v e l y ; a t 4 mm. , t h e y w e r e 1 0 . 2 a n d 1 8 .
S i m i l a r r e s u l t s a r e a v a i l a b l e on t h e o t h e r l o w e r a l d e h y d e s .
throw l i t t l e
light
ticu larly
the
testing
in
the
icals
take
b u t more
(1)
promoted
nart
step
have
in
are
presence
to
analysis
inhibition
of
as
par­
methods
of
evidence.
whether
two
are
free
rad­
indirect,
products.
Q
c o n v e r s io n , which i s
of
radicals.
certain
- 4-
step,
direct
decide
The l a s t
free
prim ary
more
adm issible
the
of
the
only
been used
than
of
p a ra -o rth o hydrogen
by t h e
( 2 ) The
and
a reaction.
satisfactory
Th e
nature
pyrolysis,
prim ary
Six methods
on t h e
reactions
( e . g . d i m e t h y l ethlP)
diethyl
ether
,
is o p ro p y l m ethyl e t h e r 12,
m arkedly through
tion
that
the
the use
of n i t r i c
uninhibited
oxide,
reactions
and d i o x a n e 1 3 )
which
proceed
is
via
an
indica­
a c h a i n mech­
anism .
(3)
to
The P a n e t h m i r r o r m e t h o d 6 ,
show th e
positions
presence
of f r e e
which has been a p p l i e d
radicals
in
the
therm al
decom­
of
c e r t a i n compounds ( e . g . a z o m e t h a n e 1 ^ and
15
acetaldehyde
) as w ell as numerous p h o t o l y s e s .
(4)
to
introduction
produce
studied.
an
them i n t o
type
of
e t h e r ' 1'®,
(5)
increase
in
the
first
and
in
the
second
20
(b)
cannot
are
surface
case,
compound b e i n g
the
been s tu d ie d
latter
in
is
This
the
cases
of
and a c e t a l d e h y d e ^ *
of
reaction
low p r e s s u r e s
gases
reaction,
at
accompanying
pressures
may be
of free
radicals;
and h e n c e
may t e r m i n a t e
gas
phase.
a
or accompanying
high
at
the
This
17
e th e rx , n-propyl
V ariations
of
the
be e x p r e s s e d
as
simple
up t o
radical
the
reaction
reaction
highest,
mechanism,
rate
integral
indications
A three-halves-order
free
at
k n o wn
amine
surface,
e ffe c t ha3
19
, and
•
alm ost c e r t a i n
sures
rate
in the
in d iv in y l
by t h e
has
chains
case,
occupied
d e c o m p o s itio n of
inert
of a chain
from a s o u rc e
e t h e r 1^,
the
foreign
for
been o b se rv e d
in
radicals
r a d i c a l mechanism e x i s t s .
divinyl
in
of
indication
acetone
of the
a free
A decrease
introduction
an
that
space
induced decom position
dim ethyl
large
the
A cceleration
indication
of fr e e
of
rate
cannot
and h as
w ith pressure
powers
a free
of
radical
the
been o bserved
other
in
pressure
mechanism.
over a long range
be e x p l a i n e d
that
of p re s ­
than
the
by a
cases
of
acetaldehyde
period,
,
divinyl
observed
at
as
those
of aceto n e
as
being
caused
tration
of f r e e
reaction
rate.
The
first
case
of
view i s
ether^,
the
22
start
of a r e a c tio n
and d i v i n y l
by t h e
time
radicals
four
and d i o x a n e ^ .
required
acetaldehyde,
and
now h e l d
free
that
to
sufficient
methods have
in
17
ether
such cases
, may b e
build
of
radicals
interpreted
up a c o n c e n ­
to m ain tain
been
spite
in
An i n d u c t i o n
brought
the normal
to
bear
on t h e
s ome d i s a g r e e m e n t ,
exist
in
both the
the
photolysis
and p y r o ly s is ,,
Th e p a r a - o r t h o
Sachsse
and
indicated
free
p a t a t 2° with
that
only
radicals,
same m e t h o d .
as
are
3
x
the
up i n
higher p ro b a b ility
of
part
that
of
the
w i t h 3 x 10“
this
ordinarily
used
result
10“ 6
compared
However,
when p a r t i c l e s
change
h y d r o g e n c o n v e r s i o n was u t i l i z e d
procedure
activating
secondary
occurrence
2
the
has
the
conversion
produced
acetone
by t h e
b e e n known t o
para-ortho
reactions
than
observed
molecules
for
by
the
fail
hydrogen
which have a f a r
former*.
* E . g . , t h e p h o t o s y n t h e s i s o f HCl i s , w i t h o u t q u e s t i o n , a c h a i n
r e a c t i o n , y e t the p a r a - o r th o hydrogen c o n v e rsio n i s u n a f f e c t e d ,
t h i s i s e x p l a i n e d by m e a n s o f a r a p i d s e c o n d a r y r e a c t i o n
H f C l 2 ------------- HCL ♦ C l
w h ic h o c c u r s t o t h e H atom a b o u t once i n e v e r y 100 c o l l i s i o n s ,
whereas
H t ’ H2 (p ) —
——H g ( o ) — H
i s e f f e c t i v e only once in every 1,00 0 ,0 0 0 c o llis io n s .
(See
B u rto n and R o l l e f s o n , P h o t o c h e m i s t r y and Mechanism o f C h e m ic a l
R eactio n s, p. 117).
p a t a t (Z* P h y s . C h e m . , B 3 2 , 4 4 - 9 3 ( 1 9 3 6 )
shows t h a t c o n v e r s i o n o f p a r a - h y d r o g e n i s c a u s e d o n l y by H
i n i t i a l l y produced as a r e s u l t of r e a c t i o n mechanism.
M itchell
decom position
and H i n s h e l w o o d 2 4 f o u n d
of acetaldehyde
that
wa9 r e d u c e d
the
to
photochem ical
1/300
of
its
velocity
by th e
vessel,
age
indicating
chain
that
in
pyrolysis
the
radicals
take
NO s u b s e q u e n t
no p a r t
radicals,
and
catalyst,
it
uninhibited
its
in view
appears
that
re a c tio n has
500°c., l e a d i n g t o
in
the
therm al
have n o t
the
fact
the
reaction
or no in h i b i t i o n ,
postulated
of
the
at
students
to
f e w mm. o f NO t o
L ittle
300.
and h i s
a
the
of
Hinshelwood
the
of
length
was n o t e d
free
addition
an a v e r ­
however,
the
idea
that
decom position.
traced
the
history
com bination w ith
t h a t NO c a n a c t
whole e x p l a n a t i o n
But
of
alkyl
as
has
a positive
yet
to
be o f f e r e d .
By m e a n s
that
lysis
free
15
the
radicals
duction
of
com plete
whereas
the
both
in
showed
free
from
radicals
aldehyde
radical
to
produces
In
presence
of
method,
the
it
has
been
shown
p h o to ly s is 2^ and pyro-
azomethane
quite
be
deliberate
at
in
inert
available
300°C.
intro­
causes
the
a short
tim e,
at
tem perature*
this
for
such a chain
addition
o f hydrogen to a ce tald eh y d e n e v e r
QC
reaction
, a l t h o u g h i n many o t h e r
first-order
low p r e s s u r e s
case
of
of
free
radicals
inconclusive.
in th e
radicals.
conditions,
the
occur.
the
conversion
is
mechanism must
high-pressure
at
that
acetaldehyde
alone
a first-order
the
restored
free
m irror
18
and Siclcman '
Furtherm ore,
been
appear
decom position
reaction
cases
Paneth
of acetaldehyde.
A llen
A free
of
rate
has
been
for
the
b y s u c h a p r o c e d u r e 2 *^.
propionaldehyde^
had,
up
to
West2 8 , u t i l i z i n g
photo-dissociation,
However,
caused
reaction
acetone,
conversion
of
the
evidence
the
time
the
of
para-ortho
found no
treated
33# and
this
hydrogen
evidence
under
44^
research,
0f
the
the
of
same
pa r a -
hydrogen
10
used
as
the
apparently
therm al
oxide
in
two e x p e r i m e n t s .
Upper l i m i t
EtCHO by a s
much a s
position
elevated
of
3 to
fraction
at
nitric
10 a t
to
50g
29
.
the
300°C*
experim ents
and
the
ditions.
Thejcorresponding ch ain
It
is
are
vealed
length
1237 f o r
interesting
a n d by t h e
tum y i e l d
in
The n i t r i c
of
free
the
oxide
radicals
note
free
v e r s i o n 2 8
is
the
reveal
that
lengths
method
is
e v e n when
pronounced
inhibition.
at
it
are
of
ature
both
only
it
is
is
by t h e
1.1,
on a c e t a l d e h y d e ,
compound y i e l d e d
and th e
fication
undergoing
presence
of
of
and
been
even
at
free
by g e n t l y
technique
at
the
even a t
to
heating
300°C.
radicals
had n o t y e t
as
a detector
they are
present.
of
propionaldehyde
time
of h i s
first
reported
that
In a subsequent paper
the m irro rs
could n o t d e te c ta b ly
did
con-
a quan­
a possibility
w hich time he
radicals.
photolysis
free
30
re­
para-ortho
alm ost c e r t a i n
there
by P e a r s o n
a t which p y r o l y s i s
aldehyde
450°C.
apparently u n re lia b le
chains
photolysis
was s h o w n 2 5 t h a t
s a me c o n ­
which has
The P a n e t h m i r r o r m e t h o d was a p p l i e d
neither
and f o r a c e t ­
and 30 f o r p r o p i o n a l d e h y d e .
acetone,
radicals
photolysis
there
experim ents
a chain le n g th
P a n e th m i r r o r method30 e x h i b i t s
Only where
undergoing
of
p h o t o c h e m i c a l decom­
100-190 under the
acetaldehyde
to
as y ie ld in g
N itric
of p y r o ly s is
1 0 0 mm. p r e s s u r e ,
aldehyde,
2 0 0 mm.
the
para-hydrogen)•
rate
However,
mechanism in
te m p e ratu res24 is undoubtedly a chain
oxide
chain
inhibit
and P a t a t 2 3 found
of propionaldehyde
radical
(again u t i l i z i n g
been found
reaction:
the
decomposing v i a a f r e e
decom position
has
of
Sachsse
to
a tem per­
occur,
acet­
remove m e t a l l i c m i r r o r s ,
wa s c o n f i r m e d .
This
modi­
been a p p lie d
the
photo­
to
lysis
of propionaldehyde,
taken
in
order
t
to
carry
and
out
the
this
present
r e s e a r c h was u n d e r ­
experim ental
work*
II.
A.
D escription
The a p p a r a t u s
that
of
C.
method0 .
A , 6 , C,
was,
the
the
Fig.
acid
L is
stances
final
glass
into
and a l e n g t h
necting
a tube
it
little
m odification,
1 c m.
nection
Pressure
all
In itial
course
of
of
like
cm.,
vessel
this
the
other
wa s
system ,
leading
in
manometer,
to
amounts
propionaldehyde
of
one mol a n d
in
a graph,
various
the
fig.
The wide
turnings
to
quartz
2
tube,
sub­
of
5 cm.
arm c o n ­
adm itting
reservoirs
C a n d D.
below,
d irect line
being
in con­
by s t o p ­
between
k e p t wide
by n u m e r o u s c o m p a r i s o n s
of 2 4 .2 :1 .
and o f ace t o n | ? F a n
pressures,
and
the
the
of
w ith
Measured
through the
times
vapor v e lo c itie s
the
open in
was m e a s u r e d b y means
have a slope
in itial
are
of passage
recorded
.
portion
guard
seal
wa s c o n t r o l l e d
the
pressure
a vertical
at
to
flow ing vapors
found,
tube
w ith a side
of
against
J,
of
operations.
and r e c o v e r y r e s e r v o i r s
of
with a diam eter
a r r a n g e m e n t ma y be s e e n
This
(because
introducing
A,: a n d w i t h a r i n g
stopcocks
of a run.
for
with
and D o f a c e t o n e .
tin d e r vacuum
equipped
m a n o m e t e r F, r t i i c h was
quartz
vacuum p u r i f i c a t i o n
T r a p B,
degassing
of the
set-up*
propionaldehyde
their
Paneth m irro r
the
a n d was u s e d
system.
20
diagram o f
even w hile
in d ia m e te r
of
with
,
joint),
the
p h o t o l y s e 3 by t h e
the
reservoir
with
The p u r p o s e
The
w ith
a sohematic
A wa s d e t a c h a b l e ,
a ground
6
fatty
and D c o n s t i t u t e
Vessel
cock
used
of Apparatus
e m p l o y e d b y B u r t o n 3 1 a n d by H e n k i n a n d B u r t o n 3 2 i n
studies
C as
EXPERIMENTAL PART
the
the
tube
entrance
wa s 5 . 2 2 mm.
-1 0 -
a t G contained
silver
of m ercury vapor.
in d ia m e te r ,
measured
Fig.
1--Diagram
of
apparatus
&
o
+J
Upper c u rv e : time r e q u i r e d f o r passage
o f o n e mo l o f v a p o r o f p r o p i o n a l d e h y d e
or acetone through system.
Lower c u r v e : l i n e a r v e l o c i t y - o f v a p o r
a t beginning of c o n s tr ic t e d tube.
O ■ time of p a s s a g e .
V - linear velo city
P m i n it i a l pressure
of vapor
O p e n c i r c l e s : o b s e r v a t i o n s o n C®H«pHO
C l o s e d c i r c l e s r o b s e r v a t i o n s o n TCh ^ , ) j,CO
volum etrically,
G and E,
allow ing
8 2 * 5 cm.
the
for
the
graded
E,
cooled
aldehyde
steam
length
seals
w ith
and
liquid
acetone
below)
was m o v a b l e .
5,000-volt
It
cover
over
source
reaction
an
tube.
beginning
side
effective
the
of
Th e
the
quartz
delim ited
the
la m p was
of
the
quartz
The
output
of
overall
at
in
was c o n t r o l l e d
by a f i x e d
current
in
prim ary
amperes
by m e a n s
correct
sm all
The
quartz
and
the
tube
and a
55°C .,
be g r e a t e r
all
4 0 c m.
H i g h vacuum t e c h n i q u e
p u mp ,
than
the
fixed
it*
this
along­
zone
was
for
the
m irrors
transform er,
constant
olt
lamp:
figure.
experim ents,
transform er
1 1 0 —v
at
the
6.4
used
to
supply l in e .
were
the
lamp
located
lead,
in
18 c m . ,
exit.
throughout.
b a c k e d by a Hy-Vac o i l
-1 1 -
from
tem perature
the
wa s u s e d
quartz
and th e
kept
away fro m t h e
the
tem perature
in
the
which i l ­
of
and
.
The
quantitative
from
and E t z l e r
l a m p wa s
shutter.
an A d ju s t- A - V o lt
downstream
m ercury-diffusion
at
low p r e s s u r e ,
16 c m.
mm.,
2
long,
(described
tubing,
The
trap
was 15 cm.
e n d e d 2 0 cm.
of
o f w h i c h was
reservoirs
antim ony,
zone
centers
recover propion­
spiral,
of
at
experim ents.
constant-current
fluctuations
m etal
the
of
length
region*
could n o t
lamp,
the
m irrors
quartz
a distance
shields
fixed
by R o l l e f s o n
5 mm.
kept constant
the
the
of
between
Term inal
m irrors,
and guard
illum inated
tube
tube
lead
described
constricted
by c o p p e r
of
the
to
subsequent
was a q u a r t z
spiral
was
between
was u s e d
in
test
(L)
mercury a rc ,
wa s a n i n e - t u r n
lum inated
both
length
) was 70 cm.
fo r use
j a c k e t H,
light
quartz
nitrogen,
to
The
of
constricted
and b e n d s,
and
sufficient
and
effective
stopcocks
The a c t u a l
of
G lass
and
A glass
pump,
produced
the n e c e s s a r y
p o r pump a n d
nitrogen,
means
of
the
m anifold
and a vacuum o f
a Mc L e o d g a u g e )
runs.
From t i m e
to
in
bottom
this
the
vacuum,
of
had to
a removable
if
t>r«u.ghout,
reservoirs
C a n d D,
small
better
before
amounts
preventing
of
the
the
the
of
grease
all
the
absence
transfers
aldehyde
of
was d i s t i l l e d
containing d r ie r ite
two d a y s .
d istilled
a clean
free
m aterial
wa s
true
boiling-point)
containing a trace
glass
vessel,
this
generous
fraction
taken
of the
stoppered
to
product
and t h i s
flask
stand
wa s t h e n
preservative-
(to
rejections,
of hydroquinone.
poly­
was n e c e s s a r y
allowed
im m ediately r e - d i s t i l l e d
w ith
and
fraction
a ground-glass
of
the
E astm an Kodak
speed
The m i d d l e
fraction
into
sealing
oxidizes
and h y d r o q u i n o n e and
The m i d d l e
into
of th e
into
the
wa s e m p l o y e d .
of a p r e s e r v a t i v e ,
m aterial.
of
those
from t h e
in
condensed
stopcocks
wa s p u r i f i e d
readily
which
of
Large
Propionaldehyde
m aterial
by
or d i s t i l l e d
of M a t e r i a l s
this
liquid
maintenance
system,
exception
and L u b r i s e a l
Since
mercury va­
each s e rie s
of l i q u i d
a m o u n t wa s g r e a t .
w ith
the
(measured
Purification
m erizes
point
or
B.
product.
for
mm.,
10“ 6
trap,
the
between
wa s c o n s t a n t l y c o o l e d w i t h
be p u m p e d o u t
trap
A trap
was o b t a i n e d
tim e,
were used
in
vacuum.
obtain
into
The c o r r e c t e d
a
a vessel
boiling
wa s 4 7 . 8 - 4 8 . 0 ° C . #
T h e b o i l i n g p o i n t o f p r o p i o n a l d e h y d e s e e m s t o bg i n d i s p u t e .
V a r i o u s h a n d b o o k v a l u e s a r e 4 9 . 5 ° C . a n d 4 8 . 1 - 4 9 . 1 C* a t 7 4 0
mm. , a n d 4 8 . 8 ° C . a t 7 6 0 mm.
W in k le r , F l e t c h e r , and H inshelw ood
( P r o c . R o y . S o c . ( L o n d o n ) 1 4 6 A , 3 4 5 , ( 1 9 3 4 ) ) q u o t e 4 8 . 5 - 4 9 . 5 C.
as t h e i r middle f r a c t i o n , while Pearson observed 49.5°C.
This
fraction
was s t o r e d
o vernight in
-1 2 —
trap
A,
w ith
drierite
and
hydroquinone
but not under
atures
vacuum.
It
and e v a c u a t e d .
at
0°C .,
was
then cooled
Follow ing
sisting
o f warming
to
cooling
to
tem peratures,
repeated
dry-ice
several
repeatedly
line,
and
a series
room t e m p e r a t u r e
tim es,
from A to
in p o sitio n
B,
f r o m B t o A,
the
the
to d r y - i c e
apparatus
temper­
of operations
with stopcock
and e v a c u a t i n g f o r
propionaldehyde
w ith
in
1
con­
closed,
25 m i n u t e s ,
was d i s t i l l e d
s to p c o c k 2 open
to
the
w ith stopcock 2 closed*.
vacuum
Finally,
ix w a s
* A f u r t h e r d e g a s s i n g o p e r a t i o n wa s p e r f o r m e d o n l a t e r s a m p l e s
by p a s s i n g p r o p i o n a l d e h y d e r e p e a t e d l y t h r o u g h J w i t h s t o p c o o k
10 o p e n a n d E c o o l e d i n l i q u i d n i t r o g e n *
distilled
ried
and
o u t by u s e
room and
first
into
solid
stored
of
the
of
a p p ro p ria te
the
in vacuo
final
These
tem perature
carbon dioxide
d istillatio n
fractions
in c.
difference
ice.
The l a s t
was r e j e c t e d .
distillatio n
means and f o u n d
distillations
to
be
in
free
betw een the
fraction
Th e f i r s t
vacuo were
of
were c a r ­
of
the
and l a s t
removed by
both a c id
and w a t e r y
** F a i l u r e t o p e rfo rm t h i s f r a c t i o n a t i o n i n vacuo would i n e v ­
i t a b l y le ad to q u e s t i o n a b l e r e s u l t s , as m easurable q u a n t i t i e s
o f a c i d w ere fo u n d a s t h e r e s u l t of th e s t o r a g e o f p r o p i o n ­
aldehyde in a i r , even in g ro u n d -g la s s stoppered b o t t l e s cont a i n i n g hydro q u in o n e and d r i e r i t e .
See T a b l e I .
Acetone
ified
from the
through
N al-acetone
Werner34,
the
b e s t E i m e r a n d Amend p r o d u c t wa s p u r ­
crystallization
complex,
according
and f r a c t i o n a l l y
the c o r r e c t e d
range
of
5 6 .1 ° C .30iO .
This f r a c tio n
in
the
no h y d r o q u i n o n e
of
both w ater
into
the
the
distilled,
in
in vacuo
to
and d e c o m p o s i t i o n o f t h e
55*09°-56.12°C*
method of S h i p s e y and
the
fraction
(cf.
was d e g a s s e d
P earso n 's
propionaldehyde,
was u s e d .
distillate
and r e d u c in g a g e n ts
apparatus.
W ater was
-1 3 -
before
tested
boiling
figure
and d i s t i l l e d
s ame m a n n e r a s
The
used
except
was f o u n d
i t was
to
that
be f r e e
introduced
f o r by the c o l o r a t i o n
TABLE I
ACID CONTENT OF SAMPLES OF PROPIONALDEHYDE
Sam ple and t r e a t m e n t
A cid p r e s e n t
A. U n t r e a t e d , s t o r e d o n e h o u r
in g la e s-sto p p e re d b o ttle
1*85#
B. U n t r e a t e d ; s t o r e d t h r e e h o u r s
in glas3-stop p ered b o t t l e
2*22#
B* U n t r e a t e d ;
fresh
from
b o ttle
1*07#
U n treated ;
fresh
from
b o ttle
1*07#
one d a y
1*10#
B. S t o r e d
over d r i e r i t e
B. D i s t i l l e d a n d m i u d l e f r a c t i o n
s t o r e d o v e r h y d r o q u i n o n e and
d r i e r i t e one d a y
B. A b o v e s a m p l e r e d i s t i l l e d a n d
m iddle f r a c t i o n d i v id e d in to
p a r t s ( a ) and ( b ) :
( a ) d i s t i l l e d in o rd in a ry a p p a ra tu s
w ith th erm o m eter
th en d i s t i l l e d in g r o u n d - g la s s
a p p a ra tu s w ith therm ocouple
( b ) d i s t i l l e d in o rd in a ry ap p aratu s
w ith th erm o m eter
then d i s t i l l e d in g ro u n d -g la ss
a p p a ra tu s w ith therm ocouple
B (b)
d i v i d e d i n t o two p o r t i o n s a n d
a llo w e d to s t a n d 24 h o u r s ;
(1) over hyd roquinone
(2) alo n e
C— U n t r e a t e d ;
and d r i e
(1 ) one
( 2 ) two
sto red
rite
day
days
0*63#
0
* 8 ^#
0 .3 3 #
0 .5 4 #
0*15#
0 .3 6 #
0 .92#
over hydroquinone
0*99#
0 .9 9#
of
a trao e
a am j ie
liq u id ;
re te n tio n
about
w ith
anhydrous
of the
by th e
in g
of
*00002
a 3 cc.
copper
the
su lfate
absence
of
the
g*
o f KMnO^ i n
sam ple
of
co lo r
of
of
shaken
w ith a
red u cin g
an aqueous
5 oc*
ag en ts
tube
J,
in
used
because
when a l l o w e d
cap ab le
it
is
of
of
th is
ap p aratu s
of m irro rs
occurred*
tran sp aren t
in
rep eated
th is
to
h eatin g
in
w ith o u t d efo rm atio n ,
p o ratio n
a high-vacuum
A tin y d ep ressio n
tu b e,
1 6 cm*
an o th er
one
m etals
w ere
stick s
of
been
from
40 cm,
scraped
an a i r
lam p,
from
C .P .
off.
acid ,
current
in to
and
th e
form
a fte r
th e
q u artz
tube
ri^ ed
w ith
w ater,
th ese
than
of
the
2000
flam e
capable
bottom o f
the
m etal
lead
the
of p e lle ts
The
before
is
lam p c o n t a i n e d
the
m etals
lig h t
gas-oxygen
co n tain ed
the
in
Q u a r t z was
(g reater
the
tech n iq u e
ft,),
(even
of
in c o r­
th is
q u artz
system *
blow n
in tro d u ced
the
w ith n i t r i c
the
stan d
was q u a r t z
u ltra-v io let
research
u n d e r vacuum)
in to
co n tain ­
to
M irro r
in te re st
in v o lv ed
shown
aceto n e.
w hich re m o v a l
w av elen g th s
is
of
was
so lu tio n
C.
The c e n t e r
oc.
5
ad h erin g
was
reserv o ir;
antim ony*
carved
oxide
th o ro u g h ly
and d rie d
sam ples
from
film s
had
cleaned
by h e a t i n g
w ere
The
in
in serted * .
■ ^ C le a n in g w i t h c h r o m i c a c i d was f o u n d t o i n h i b i t c o m p l e t e l y
t h e r e m o v a l o f m i r r o r s e i t h e r by p r o p i o n a l d e h y d e o r a c e t o n e .
I n t h e f i r s t ^5 e x p e r i m e n t s , t h e r e was n o m i r r o r r e m o v a l a s
a r e s u lt of t h i s .
Once
fu lly
th e
q u artz
ev acu ated
to
tube
was
prevent
th e
sealed
an
in cip ien t d u ll
red
glow
p lace,
d islo d g in g
a n d a vacuum o f 10 ^ was o b t a i n e d *
to
in
from
-1 4 -
The
one
of
the
q u artz
end to
the
air
was c a r e ­
m etal p e l l e t s ,
tube
was h e a t e d
an o th er,
except
for
the
v icin ities
The
tube
of the
was a l l o w e d
to
c o o lin g
and e v a c u a tin g
th ro u g h
the
to E ( a t
tube a t
liq u id
w as r e p e a t e d .
and th e
the
tube
q u artz
one end
h eated
tiv e
the
the
ju st
w alls
adsorbed
and
ev acu ated .
gases
It
th is
to
tu b e and
the
was r e m o v e d
from t h e
F o r e a c h experim ent*
m anner of P e a rso n
w ith
to
series
each
30
the
the
polym eric
resid u es
n e a r the
ap p aratu s
m irro rs
d en sity
by g e n t l e
and w orking
was
and
ited
off,
u pstream
from
be d e p o s i t e u .
The
the
each
en tire
surface
fiv e
the
10
of
in
any fo re ig n
—b
after
the
b y c om ­
tu b e.
P rio r
mm. o r b e t t e r w a s
of tra c e s
o f m etal
in a g a s-o x y g en
the
a p ilo t
w hich t e s t
and
flam e*
m etal r e s e r ­
source
of vapor
m i r r o r was d e p o s ­
m irro rs
m i r r o r was t o
were t o
sen sitize
m ight l a t e r
m i r r o r s u b s e q u e n t l y d e p o s i t e d w as s u p p o s e d
-1 5 -
The s m a l l
a g lass
tow ard
u po n, w h i c h m i r r o r s
respec­
and d i s c a r d e d .
la te r,
th is
w ere
p re p a ra tio n of th e
The
p o in t a t
purpose
of
flo w in g .
m inutes
off,
glow from
th e ir
being d e te r m in e d
h eatin g
p ropionaldehyde
to
were d e p o s i t e d
tube c l e a r e d
v o ir w ith th e
shut
th is
a vacuum o f
q u artz
lam p
in
red
co n tain ed .
smoked d e p o s i t
of ru n s ,
and
startin g
,
a stan d ard
o b tain ed ,
used
shut
tre a tm e n t purged
m etals
w hich th e y m ight have
then
u n d e r vacuum,
make t h e m a d h e r e
q u artz
surface
w as
process
m etal p e l l e t s
th is
A fter
was p a s s e d
h eatin g
a d u ll
the
that
of p ro p ionaldehyde
p ariso n
to
b eliev ed
vapor
and th e
F in ally ,
is
am ounts
rep eated .
room t e m p e r a t u r e )
vapors
tim e,
m etal r e s e r v o i r s .
process
from C ( a t
o f flo w in g
but
and th e
p ropionaldehyde
o n c e more h e a t e d
o th er,
the
the
tem perature)
su fficien tly
of
and
ag ain ,
source
was
reserv o irs.
seals
low p r e s s u r e
cooled
tube
to
cool,
n itro g en
The
graded
to
be d e p o s i t e d ;
sen sitize
the
len g th
sw ept*
of q u a rtz
W ith
tu b in g
stopcocks
6
,
o v e r w hich
7,
and
12 o p e n
q u an tities
of m etal
w ere d i s t i l l e d
reserv o irs
by m eans
of
were
allo w ed
by m eans
of
to
co o l,
the
the
of
h eatin g
5 cm.
th e
upstream
m irro r
10 w e re
•as
the
to h e a t
open to
was n e a r l y
or
ten
m inutes
same
the
sy stem .
d ep o sited
req u ired
and
for
stan d ard
q u an tity
was
found
the
d en sity
in
reason
th an
as
the
re m o v a l was
flow .
the
w ere
d ifferen t
rem ain in g
co n stan t.
req u ired
a fte r
in
th is
found
to
depend
—1 6 —
allo w
3 , 6 , 7 , 8 , 9 , and
of
of runs
reagent
suspen­
one h o u r e la p s e d
betw een
m i r r o r was d e ­
minimum
An i n t e r v a l
betw een
runs
ev acu atio n
standard
of
upstream
m irro r
to
d a y were
d istan ces
th e
from
the
the
source;
to
But
b o t h on t h e
of
ap p ro x im ately
p ractice,
o p eratio n .
were
tim e
The d e p o s i t i o n
from
of
of
m irro rs
observing
by d i s t i l l i n g
co n sid erab le
rad icals,
A series
f o r the
tak en ,
purpose
rem oved
of
not
su p p ly
p e rm it ad equate
was a c c o m p l i s h e d
p o ssib le,
S topcocks
at
of m etal
of
te st
th e
m irro rs
free
care
r u n s w ere made.
for
m etal
of p ro p io n ald eh y d e
tak in g
th is
m in u te
w ere
of
before
rem oval
th in g s
they
actio n
w henever the
more
to
the
These
a new p i l o t
order
been
vacuum,
from
such c a se s,
rem oved
such
70°C,
when o p e r a t i o n s
p recau tio n s
m irro rs
th e
about
was e s t a b l i s h e d
such
o th er
of
a ll
series,
A fter
tim e
in
the
m irro r,
com plete
any
the
m inutes
a stream
vacuum d u r i n g
be
and rem oved
th e
lam p,
to
in
p ilo t
had
th erm al d eco m p o sitio n
through
tube
above
the
when f o r
p o sited
the
ex h au sted ,
ex p erim en ts;
of
from
co n sid ered
ded,
q u artz
to
upstream
fiv e
th e
p ro p io n ald eh y d e--p resu m ab ly
b y
m etal
g as-oxyg.en f la m e .
and a f t e r
p ro d u cts
the
it
co n tro l
sin ce
the
d en sity
and
w idth o f a m ir ro r,
it
d iffu se
zone u p stre a m
body o f
the
ience*
T his
d ep o sit
to
th e
m irro rs
a w idth
of
to
the
it
elim in ate
chosen
the
the
m ain
fo r conven­
m irro r in
p y ro ly sis
o b serv atio n ,
to
and reduce
mm*,
2
by r e m o v in g
su b jected
by v i s u a l
found n e c e s s a r y
from
w as d o n e
propionaldehyde
u n til,
was
a stream
of
a t a p o in t upstream ,
was o f t h e
correct
w idth
and
densi ty .
off,
F o llo w in g
th is
o p eratio n ,
and
fiv e
m inutes
a fte r
on a n d a l l o w e d
w as k e p t
vapor
by a i r
w as t h e n
pressure,
of
the
the
of
beginning
the
if
the
q u artz
the
flow
co o lin g .
started ,
cocks
tube
W ith th e
its
1 0 ,1 2 ,
to
the
for
exposure
the
3,
w ith
both
a ll
w ere
such
th is
to
in
tim es.
m etallic
not
the
step .
of
in
th e
run.
have
any
a ten
condensed
the
the
in
since
trap
m anifold
-1 7 -
w ait,
a m irro r could
was n e a r l y
E w as d i s t i l l e d
(K)
and
fractio n ate
and s t o p ­
the
q u artz
the
p roducts
and carb o n
d e g a s s in g w hile
sto p co ck
b o ilin g
effect,
betw ai
Then
m inute
10
the
rem ained
im p u ritie s,
o r c a r b o n y l com pounds,
m easurable
len g th
disappearance
supply
vacuum l i n e
Th e h i g h
req u ired
The t i m e
The h y d r o c a r b o n s
progress,
the
reserv o ir,
th e
it
flow of
a sto p w atch .
if
by c o n t i n u o u s
a lk y ls,
reached
lam p.
A fter
re s e rv o ir v ia
had b een rem oved
polym ers,
sid ered
fo llo w in g
it
the
e x p o s i n g a 16 c m .
No a t t e m p t w as ma de t o
decom position a t
open a t
was l e f t
w hich t e m p e r a t u r e
the co m p lete
by m e a n s
p ro p ionaldehyde
and
and
was s h u t o f f .
o rig in al
d eco m p o sitio n s
soon as
actio n
l a m p w as t u r n e d
s h u t t e r down,
of
shut o ff.
m onoxide
at
tube
any p r o p i o n a ld e h y d e
back to
55°C«,
and a s
o f v a p o r w as s h u t
u ltra-v io let
up,
o fth is
the
stream
s h u t t e r was p u l l e d
of vapors
ex h au sted ,
the
h e a t up to
m i r r o r was m e a s u r e d
be d e p o s i t e d
of
to
the
w hether
w ere
becau3® the
con­
q u a n titie s
in
the
w ere
la st
tita tiv e
so
sm all
few d r o p s
th at
of
ex p erim en ts,
th e
th e
th ey
could
become
m aterial to
reserv o ir
effectiv e
be t e s t e d .
w as n e v e r
in
o n ly
quan­
exhausted
to
th is
ex ten t.
D.
It
was
found t h a t
to
rem ove
of
p ro p io n ald eh y d e.
last
lead
traces
d eg assin g
D etectio n
of A lkyl R a d ic a ls
sev e ra l p recau tio n s
m irro rs
w ith
The
of d i s s o lv e d
w as n e c e s s a r y
were n e c e s s a r y
the
p ro d u cts
of
la tte r
m aterial
seems
air
to
only
th e
to
v ery slo w ly ,
prevent
p o iso n in g
p h o to ly sis
y ield
and
the
ad d itio n al
of m irro rs# .
# T h i s w a s a c c o m p l i s h e d by r e p e a t e d l y p a s s i n g t h e p r o p i o n a l ­
dehyde th ro u g h th e q u a rtz tu b e u n d e r th e c o n d i t i o n s o f the
e x p e rim e n ts w ith o u t the d e p o s itio n of m e ta llic m ir ro rs o r
the use o f u l t r a - v i o l e t l i g h t .
P ropio n ald eh y d e
a ttack s
sto p co ck grease
and l e a v e s
resid u es
o f h ig h b o i l in g compounds (p o ly m ers o r o th e r w is e # # ) i n th e
##Such compounds a p p e a r t o p r e v e n t th e re m o v al o f l e a d m i r r o r s
in th e c o ld in th e p h o t o l y s i s o f b o th p r o p io n a ld e h y d e and
a c e ta ld e h y d e , th ro u g h th e a d s o r p tio n of a t h in la y e r o f m a te r­
i a l on t h e m i r r o r .
C f. P e a r s o n * ^ and P e a r s o n & P u r c e l l
on
the case of ac e ta ld e h y d e .
course
of p h o to ly ses,
re lu b ricatio n
of
the
of
a steam
of th e
lead
resu lt
of
around
o b serv atio n s
may h a v e
surface
In c o n tra s t
of
The m ost
jack et
m aterial
acte r
sto p co ck s,
aldehyde.
from t h e s e
ous
of
m irro rs
to
in
was a t t a i n e d
aceto n e.
n ece ssita tin g
and
the
th at
fu rth er
p erio d ic
d eg assin g
at
low
p h o to ly sis
-
too
use
18 -
of
of
It
on t h e
trap s,
was t h e
some
m irro rs,
or
resin ­
the
by c o n t i n u o u s
observed
in
th e
mu ch d i f f i c u l t y
acid
in
char­
h eatin g .
rem oval
p ro p io n ald eh y d e,
chrom ic
use
was p re su m e d
tem p eratu res,
been changed
d ifficu lties
the
p recau tio n
m irro rs.
produced
w ith o u t
A lth o u g h
of
lead
may h a v e
th e
clean in g
im p o rtan t
been
the
the
the
th is
case
p rev en ted
th e
rem oval
as
of m irro rs
soon as n i t r i c
tube,
m irro rs
and
ly sis
to
in
the
pro d u cts
hours
periods
,ih ile
th e
lead
tita tiv e
b asis,
by a l k y l
of
the
rem oved
it
im p o ssib le
w he n a l l
in
m irro rs,
th at
prove
p h o to ly sis.
may be a t t r i b u t e d
Th e
to
errors
-1 9 -
of
p h o to ­
d ep o sited
much a s
sh o rtly
vapor
w ith
two
or
rem oved,
but
experim ents
as
alk y l
the
to
taken,
estab lish
can
the
be r e m o v e d o n l y
The e x p e r i m e n t s
(sp e cifica lly
a standard
rad ical
is
unsuccessful
technique
w ith
them on a q u a n ­
p ro p io n ald eh y d e,
of
of
p h o to ly sis
p r e c a u t i o n s w ere
alk y l
serve
w ith
resu lts
put
atom s.
produce
som e s o r t
o th er
s am e m i r r o r s ,
read ily
disap p eared
p h o to ly sis,
ex perim ents
the
by a c e t o n e
as
Lead m ir r o r s
known t o
use
m irro rs tr e a te d
to
r a d i c a l s 3 3 , n o t by h y d r o g e n
rad icals
th e
p ropionaldehyde
o b serv atio n .
to
jack et
u su al.
of
number of m ir r o r s
vapor,
No s t e a m
upon u n d erg o in g
of acetone
than
q u artz
propionaldehyde.
m irro rs
F urtherm ore,
The s u c c e s s f u l
the
read ily
n ev erth eless,
th is
w ith aceto n e
m ethyl)
made
of
over
d e p o s i t i o n w ere a l s o
n atu re
m irro rs
tube
Fresh
of d e c o m p o s itio n
the
w ill.
the
p ropionaldehyde
acetone
the
were
somewhat l o n g e r
a su fficien t
re a lity
in w hich
ever re su lte d .
a fte r
for clean in g
p h o to ly sis
through
few e x p e r i m e n t s ,
found n e c e s s a r y
m irro rs,
experim ents
first
d isap o ear a t
the
cases
the
em ployed
to
p h o to -d eco m p o sitio n .
th ree
in
such
in
was n o t
lead
l a t e r run
b u t no r e m o v a l
after
it
the
remove
was
was
em ployed in
I n many o f
failed
acid
w e r e m a de
was n e c e s s a r y ,
p recau tio n s
by a c e t o n e
of referen ce.
u sin g
lead
produced
in
experim ents
p rev io u sly d isc u sse d .
E.
The
alk y l
T ests
for
of
atom ic
presence
rad icals
was
H ydrogen
Atom s
hydrogen
in v estig ated
in
through
the
the
presence
of
free
guard m ir r o r
<11
technique
d ev elo p ed
dard
m irro r
the
lead
lead
was d e p o s i t e d
reserv o ir,
v e n ien t d ista n c e
test
m irro rs
guard
test
of
n e ith e r
w ere
the
appeared,
th e
or u n t i l
reserv o ir.
w ere h e a t e d
w ith
as
aceto n e,
ven ted
when
was
the
they
less
at
le ast
its
to
th e
lead
steam *
w as
w ere
2
th at
free
at
le ast
.b
mm.
B efore
a w ide,
the
lead
the
heavy lead
reserv o ir*
proper
two
o th e r lead
w idth
p h o to ly sis
in
in
test
The
a
and
the
lead
ex p erim en ts
to
w ide
in
guard
th e
le ft
guard
in
m irro rs
hydrogen atom s,
m irro rs
case
and th e
was
d is­
w ere c o n d u c t e d
produce
lead
each
m irro rs
propio n ald eh y d e
the
some
of p r o p io n a ld e h y d e .
ra d ic als
35 mm.
con­
antim ony
te st
S im ilar
found
passage of
the
to
and
no
m irro r a t
siffl,
the
su b jected
lead
from
in clu d in g
from
a stan ­
5 cm* u p s t r e a m
reserv o ir.
p y ro ly sis
the
each ex p erim en t,
antim ony
a c o m p o u n d known n o t
It
than
of
p ra c tica lly
B oth
w ith
a b lan k .
reduced
was
both
In
stan d ard
u p stream
then
P ro pionaluehyde
to
.
to u ch in g n o r
p ro d u cts
experim en t u n t i l
from
reduced
was d e p o s i t e d
m irro rs
stream
a stan d ard
upstream
w ere
m irro r,
m irro r,
by B u r t o n
pre­
of aceto n e
pressure
o n ly
of v a p o rs
o f H g.#
•fcPaneth a n d H e r z f e l d 3 ° p r e s e n t m a t h e m a t i c a l a n d e x p e r i m e n t a l
e v i d e n c e t h a t o n l y a 1 0 mm. w i d t h o f t h e m i r r o r i s n e c e s s a r y
t o p r e v e n t p a s s a g e o f 9 9 ^ 4 $ o f m e t h y l r a d i c a l s a t 2 . 0 mm.
p r e s s u r e i n a 5 mm. t u b e u n d e r a p r e s s u r e g r a d i e n t o f a b o u t
. O a m m . / c m.
The
2 . 5 4 mm.
resu lts
pressure
co n sid eratio n
to
of guard
are
m irro r
shown
determ in e
in
the
experim ents
T able
II.
It
sig n ifican ce
-2 0 -
conducted
req u ires
of
th ese
at
careful
obser-
v atio n s.
in
the
produced
in
v e n t the
passage
dow nstream
as
the
gen
has
to
of
a ll
the
the
as
if
th ird
the
atio n s
in d icated
ex ten t
of
were
than
th is
in
are
th at
guarded,
is
lo c ated
at
th ,
at
life
in
rem oval.
ex trap o lated
the
and 59 s e c o n d s
the
cf
lam p
for
.'r o p o r t i o n a l
under
the
the
lamp
to
sp ecified
case
the
ex it
la st
case
any o f
p ra c tica lly
p o ssib ility
The f a c t
of p ro p io n a ld e h y d e,
of a c e to n e ,
lends
in
p h o to ly sis.
w eight
ad d itio n
to
Th e c a l c u l ­
to e s t i m a t e
antim ony
ex it
as
is
m irro r,
in stead
tim e
the
th at
be
of
p ro p erly
its
of
g r e a t as
because
atom s
w ill
of a t
o f rem oval
tobs»»
hydrogen
56 s e c o n d s
the
the
tim es
of a l l
-
21-
It
rela­
in
p a r t F,
the
antim ony
fo r pro p io n ald eh y d e,
of rem oval
co n d itio n s.
tim e
w o u l d be e f f e c t i v e
seen
Th e r e l a t i v e
o a rtic le s
cus­
such
of an unguarded s ta n d a rd
aceto n e.
the
sto p
of P a rt D.
d esigned
The
rem oval
a t o m s a n d m i r r o r —a c t i v s
ly
the
a stan d ard
F urtherm ore,
tim e
T his
be a p p r o x i m a t e l y 0 * 9 a s
of
only hydro­
effect*
th e^ latter d is ta n c e ,
long
m irro r^at
II
2 4 - 3 3 cm.
w ould
tiv ely
its
of
attack ed
t h a t hy d ro g en atom s,
T able
suppose
tom ary d i s t a n c e
the
in
us
observed
in
nrcduced
secondary
be
o b serv atio n s
in
If
so lo n g
m irro r w ill not
p resen t.
m irro rs,
Let
a m irro r,
guard
pre­
an a n tim o n y m i r r o r
w idth.
by t h e
are
and
of s u f f i c i e n t
are
guard m ir r o r w i l l
is
p o ssib ility :
rad icals,
rad icals
be a t t a c k e d ,
no g u a r d
fa ster
lead
rad icals
antim ony m ir r o r w i l l
attack ed
alk y l
only alk y l
guard w ill n e v er
guarded antim ony
the
if
a perfect
th e
produced,
been e l i m i n a t e d
th at
are
from
atom s a r e
fast
p lace,
a p h o to ly sis,
guard m i r r o r
them and
as
first
is
num bers o f h y d ro g e n
so rts
m u s t be i n v e r s e ­
o f antim ony m ir r o r s
ap p aren t,
then,
th at
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t h e m a x im u m f r a c t i o n
p a rtic le s
o f H atom s
in p ro p io n ald eh y d e,
(2 ) i n
R eferrin g
aceto n e,
to
T able
and 310 i n d i c a t e
II,
it
fav o rab le
co n d itio n s.
d ep o sited
s e v e r a l days b efo re
the use
If
it
are
is
lfcr2fo o f t h e
ex cluded
w ith
on p h o t o l y s i s ,
are
cause.
m irro r,
the
lead
lead
second
case
The n e e d
for
T h e s e tw o
co n sid eratio n .
are
resp o n sib le
fo r the
co m p rise m ore th a n
p articles
to
in p ro p io n a ld e h y d e .
produce hydrogen
tfcken a s a b l a n k ,
is
th at
th is
the
escap in g a lk y l
fractio n ,
upper lim it
t 0 b g#
necessary.
even tho ugh
If
th is
are
w hich e sc a p e d
antim ony
in the
in terp retatio n
failed
rad icals
is
produced
to r e a c t w ith th e
i t was much w i d e r t h a n t h e o r ­
In co n sid eratio n of
c a n be d e s e n s i t i z e d ,
guard m irro rs
rad icals
of rem oval observed
of p ropionaldehyde
guard m ir r o r ,
w hich le a d m i r r o r s
th at
ap p aren t.
t h e n 4/o-lOjS o f t h e s u r v i v i n g a l k y l
p h o to ly sis
e tic ally
th e
tim e o f re m o v a l o f an u n g u a rd e d
guard m irro r ex p erim en t,
in th e
is
known n o t
t u , d iv id e d by th e tim e
co rrect,
t h e m i r r o r was
ex p erim en t;
they can n o t
In such a case,
ob v io u sly
o f h y d ro g en atom s.
decreased.
A nother p o s s i b i l i t y
is
the
case,
from f u r t h e r
aceto n e,
143
n o t co n d u cted u n d e r th e m ost
first
to ta l m irro r-activ e
may be s l i g h t l y
th a t E xperim ents
fractio n s
assu m ed t h a t H atom s
the r e s u l t s
atom s
seen
o f a m i r r o r o n l y SO mm. w i d e .
antim o n y m i r r o r rem oval,
the
the
fre sh ly -d e p o site d m irro rs
experim ents
If
is
how ever, w ere
In
56/tjj. =
5 9 /tj^ ^ e^
abnorm ally la rg e
These e x p e rim e n ts,
w ide,
among t h e m i r r o r - a c t i v e
is
(1)
Involved
(fg)
can n e v e r be
-2 2 -
th e num erous ways i n
it
Is
en tirely
p o ssib le
co m p letely e f f e c t i v e
in
sto p p in g a lk y l ra d ic a ls
In p ropionaldehyde
rem oval o f antim ony is
the
o th e r hand,
atom s,
to
th e
vapor,
caused en tirily by a lk y l
p o ssib ility
the e x te n t o f
1
o f th e
^ -2^ o f th e
and
the
ra d ic als.
presence
On
of hydrogen
alk y l ra d ic a ls ,
cannot
be ex clu d ed .
G uard m i r r o r s
the
case
alk y l
a r e muoh m o re e f f e c t i v e ,
of aceto n e.
rad icals)
dehyde.
to
A ntim ony m i r r o r s
known to b e
n o ticeab le
b e e n made on t h e
lead
o n ly a f t e r
of h a lf-liv e s
p ropionaldehyde
ly sis
or p h o to ly sis,
S ince
co n sisten t
o r acetone
w ith o u t
tim es
the
no u n u s u a l d i f f i c u l t i e s ,
in d eterm in atio n s
p a rticles
o b tain ed
it
effect
in ro a d s have
of free
rad icals
use
undergoing e i t h e r
o f a steam
say
was d e c i d e d t o u s e
from th e
12c
/o,
mi rro t-ao tiv ei p artic le s
the h a l f - l i f e
of free
h a lf-liv es
tw o
fr o m p a r t E,
in th e
p resen ted
antim ony m ir r o r s
of th e m irro r-a c tiv e
compounds i n v e s t i g a t e d .
th at
th e
o nly a
of
produced in p ro p io n ald eh y d e,
T his
of ra d icals,
by means o f th e
In fa o t,
use
ln d lo ates
th at
is
w h ile
50^ g r e a te r
than
th at
Id en tificatio n
observed h a l f - l i f e ,
of aiitlm ony m i r r o r s
-§3-
is
It
h ig h est
observed h a l f - l i f e
m ethyl r a d i c a l s
eth y l ra d ic a ls .
the
pyro­
jack et*
c o n c e n t r a t i o n o f h y d r o g e n atom s can c a u s e
in crease,
of free
and the
and antim ony m ir r o r s
of th e
oan r e a d i l y be o a l o u l a t e d ,
sm all
p ro p io n al­
o f l e a d m i r r o r rem o v al w ere n e v er
o b ta in e d w ith p ro p io n ald eh y d e,
p o ssib le
serio u s
(by s t r a y
was fo u n d t h a t a n t i m o n y m irroars c o u l d be rem o v ed
by e i t h e r
alone
p resen t,
in
In
guard.
F. D eterm in atio n s
It
a re rem oved
a much s m a l l e r e x t e n t t h a n
No H a t o m s a r e
on an tim o n y i s
as ex p ected ,
is
eq u iv alen t
fe a sib le .
to
the u se
o f lead m irro rs
except
for
the a b s o lu te
v alue
o f the
tim e o f
d isap p earan ce.
The q u a r t z
in
the
4 to
tu b e was o l e a n e d ,
d ep o sitio n o f
37 c m.
( 2 3 ♦_
in
2
)°C .
The a v e r a g e
from th e
The d i s t a n c e
tim e
lig h t
(T able I I I ,
fig .
source
-
a
d is­
III).
in to
(XP 2 - X i 2 )
2W
fo r th e
change o f v e l o c i t y a t t r i b u t a b l e
reactio n
20
cm. m
d i s t a n c e t o lam p e x i t fro m
b eginning o f c o n s tr ic te d zone.
V r
1788 o m ./s e o . f n r b o th a c e to n e and p r o p io n ­
a l d e h y d e a t p ■ 2 . 5 4 mm. o f H g.
a -
p r e s s u r e g r a d i e n t ■ . 0 2 9 6 mm. H g / c m .
( a t e r m i n a l p r e s s u r e o f 0 . 1 mm. H g
i s assum ed).
c m. p l u s
20
in teg rated
d istan ce
ex p ressio n
for
from m i r r o r
the
rate
to
of a
len g th .
lam p.
first-
is
In
the
( A / A Q)
« k
co n cen tratio n
a rb itrary
sta r t,
of tran sp o rt
* 1-
The g e n e r a L
the
ag ain st
ap p aratu s:
Xp z
at
p lo tted
can be t r a n s l a t e d
37
in acco rd an ce w ith th e form ula:
z ■ tim e
_t t h e
o f rem oval o f antim ony m ir r o r s
on a g r a p h
X 0 - Xi
Y
and a t
g rad ien t.
In th is
w here A i s
2 . 5 4 ± . 0 5 mm. p r e s s u r e
of tu b i n g w ere
lig h t
w hich fo rm u la c o r r e c t s
order
A ll
source
from th e
of tran sp o rt
pressure
lamp i n n e a r l y 100 e x p e r i m e n t s *
tim e
len g th
z -
to
from
at
at
was u s e d
random d i s t a n c e s
co nducted
each cen tim eter
tan ce
stan d ard m irro rs
away fr o m t h e
e x p e r im e n ts were
and antim ony a lo n e
tim e.
A0 i s
and t Q th e
tim e
*T
In
( t - t g )
or In A s
(or a c t i v i t y )
of re a cta n t,
the c o n c e n tra tio n
at
th e
- k t * co n st.
start* .
o f the
and
reactan t
In e ith e r
eq u atio n ,
6 .3 6 ,3 7
2 5 ,3 8
oommon w i t h P a n e t h
, P earson
t and t h e i r c o -w o rk e rs,
th e r e c i p r o c a l o f m irro r-re m o v a 1 tim e as a m easure o f
a c tiv ity or co n cen tratio n .
____________________________
' 24-
TABLE I I I
SAMPLE CALCULATIONS FOR F I G .
Time o f
tran sp o rt
XV & V I AND TABLES I I I B
fr o m lam p e x i t
z r X--X- SV 7 ”
-
(m ethod
1
v 5
mT
P a n e th and L a u ts c h )
a
(X«2 - X ] 2 )
2Vn P
E f f e c t i v e c o n s t r i c t e d zona
i s 8 2 . 5 cm. l o n g
I n i t i a l p r e s s u r e - 2 . 5 4 mm.Hg
r P
F i n a l p r e s s u r e - 0 . 1 mm. Hg
z r
of
& IIIC
X-j r
2 0 om.
at
lamp e x i t
Vg -
1788 o m . / s e c . f o r b o t h
vapors
a * g rad ien t f;(2 .5 4 -0 .l)/8 2 .5
. 0 2 9 6 mm. H g / c m .
r X* - 20 - .0 2 9 6
( X .2 - 4 0 0 ) [ .* 1 (X _ -.0 0 5 8 2 X * -1 7 .6 7 2 )
*•
2“ 2T5'4 9
-1 m s 2
2
V a p o r .................................
A verage d i s t a n c e o f
m i r r o r s fro m lam p
(cm)
(X ^ -X ^ )•
EtCHO
•••
A v e rag e d i s t a n c e from
s t a r t of c o n s tric te d
zone
( c r a ^ ( : Xr>)«*
EtCHO
MegCO
9
26
6
24
29
46
26
44
.
Time o f t r a n s p o r t fro m
l a m p e x i t s- z ( s e c . )
( c a l c , from above f o r m .)
3 .6 0 x 10~5
8 .9 6 x 1 0 -3 2 .4 5 5
A verage rem oval tim es
o f s t a n d a r d Sb
m irro rs (s e c .)
(=d)
114
R elativ e a c tiv ity of
f r e e r a d i c a l s -A
s 1 /d
8 .7 7
x 10“
N a tu ra l log of ac­
t i v i t y e Ln A
MegCO
—4 . 7 4 5
« atv i
xlO
5
3Z±\xl°
300
3
3 .3 3 x
—5 . 7 1 5
83
„
10 “ 3 1 2 . 0 5
214
_
x 10_ 3 4 .7 x J X r
- 4 .42 5
- 5 .375
1
P ig . 3'—Time o f antimony m irror removal in p h o to ly s is o f propion aldeh-H e.
500
i — tim e o f m i r r o r rem o v al
x^-x-j = d i s t a n c e o f m i r r o r
from lam p e x i t
300
~V
ZOO
too
th e
graph
of In A a g ain st
reactio n s,
slo p e
produce
has
the
a
w ill,
stra ig h t
same v a l u e
The d i s a p p e a r a n c e
th e m irro r
t,
as
lin e
k but
of free
h a lf-liv es
m easured**,
it
of
to
th e
case
o f n eg ativ e
th e
o p p o site
ra d ic als
behave
of first-o rd e r
slo p e,
w hich
sig n .
under th e
co n d itio n s
of
a firs t-o rd e r reactio n * .
38
^Ttie' f i n d i n g s o f P a n e t h , H o f e d i t z , a n d T f u n s c h
seem t o con­
s t i t u t e an e x c e p tio n or a r e b u t t a l to t h i s s ta te m e n t, b u t a
r e o a l o u l a t i o n o f t h e i r d a t a shows t h a t t h e r e c o m b in a t io n o f
m e t h y l r a d i c a l s i n t h e i r c a s e d o e s show a f i r s t - o r d e r lav/.
T his r e c a l c u l a t i o n is in c lu d e d in an a p p e n d ix .
S in ce
m ethod a p p e a r s
In
sev eral free
s h o u ld be
as
ra d icals
p o ssib le
to
have
alread y been
ch aracterize
unknown
* * P a n a t h a n d o o - w o r k e r s 6 , 3 7 h a v e g i v e n t h e h a l f - l i f e o f CH^
a s . 0 0 5 5 s e c . a n d o f C*>H5 a s * 0 0 3 9 s e c . i n
6 mm. t u b e s
i h HP
stream s.
G la z e b r o o k and P e a r s o n ( I . 0 . 3 . 1777 (1 9 3 6 )) f i n d
.0 0 4 4 s e c . a s th e h a l f - l i f e o f is o p r o p y l r a d i c a l and .0 0 4 s e c .
a s t h e h a l f - l i f e o f n o r m a l p r o p y l ; and l a t e r ( J .C .G . 589 (1 9 3 9 ))
d etected
f r e e p h e n y l r a d i c a l s , b u t t h e h a l f - l i f e was n o t
m easured.
The f r e e p h e n y l r a d i c a l s w e re p r o d u c e d i n t h e
p h o to ly s es o f acetophenone and benzophenone.
p a rtic le s
the
f r o m new s o u r c e s
h a lf-life.
k by th e
T his
IV
the
fo reg o in g
are
p lo tted
of m irro r
averaged
lin e .
related
by m easurem ent o f
to
the
re a ctio n
co n stan t
are
th e
in d ic a tin g
are
each
slo p e
p lo tted
the
oase
eaoh
is
of th e
a first
order
g rap h s draw n
In
the
and
in
of
th e
th e v alu es
second,
on a n a r i t h m e t i c
the
rep resen ted
straig h t
reactio n
lin e
zone.
the
o f the
The r a n g e
fig .
co n stan t
A straig h t
p o in ts,
by a v e r t i c a l
in
them selves
lo g arith m s
scale.
of th e
recip ro cals
o en tim eter
-2 5 -
in a cc o rd a n ce w ith
first,
mean p o s i t i o n s
averages
rem oval in
The
)/k
on s e m i- lo g p a p e r ,
are
in
2
sp ecificatio n s.
draw n t h r o u g h
th em selv es
(In
(a an d b)
a o tiv itie d
is
is
rad icals
ex p ressio n
F ig u res
lin e
free
q u an tity
t_x r
of th e
of
IV i s
w hich
tim es
o f v alu es
stra ig h t
-100
o f 180 and a h a l f - l i f e
TABLE I I I
Free R a d ic a l
B
C o n cen tratio n s
in P h o to ly sis
o f P ro p io b ald eh y d e
D iet,
from
lam p
(cm . )
<Xp - X l )
E xpt.
No.
3 .5 -4 .4
190
227
228
110
115
135
120
191
229
230
70
63
105
79
1
170
192
231
68
93
70
77
-4 .3 5
2 .4 5 5
6 .5 -7 .4
232
91
91
-4 .5 2
2 .8 5
7 .5 -8 .4
146
171
193
233
234
80
118
108
112
106
-4 .6 7
3 .2 25
14 7
19 4
235
236
98
135
116
105
114
-4 .7 4 5
3 .6 0
172
237
152
127
140
-4 .9 5
3 .9 75
165
238
134
123
129
-4 .8 7
4 .3 2 5
166
195
239
128
118
141
129
-4 .8 7
4.6 8
196
240
132
155
144
167
241
144
135
140
-4 .9 5
5 .3 8
149
187
188
247
153
168
156
180
18 1
-5 .2 1
5.7 1
4 ^ 5 -5 .4
8 .5 -9 .4
9 .5 -1 0 .4
1 0 .5 -1 1 .4
1 1 .5 -1 2 .4
1 4 .5 -1 5 .4
220
242
-4 .7 9
z
« tim e o f t r a n s - ,
p o r t ( s e c xlO “ :
(b asis:
n e a r e s t cm .)
1 .6 6 8
2 .0 6 5
110
t
1 3 .5 -1 4 .4
Ln A
—- L n d
CO
cr>
.
1 2 .5 -1 3 .4
r
d
a v e . tim e
of d isap pearance
(se c .)
CO
to
•
5 .5 -6 * 4
Time o f
m irro r
d isap pearance
(se c .)
5 .025
X -X}
E xpt.
No.
Time o f
d
Ln A
m irro r
;-L n d
*<■..
d ieap pearaiice
_______________________ ________ ( s e c . )___________________________________
1 5 .5 -1 6 .4
168
197
203
217
176
168
191
-5 .2 6
6.0 5
222
261
128
195
195
-5 .2 8
6 .16
152
199
223
243
247
275
228
164
227
205
220
-5 .4 0 5
6
1 8 .5 -1 9 .4
224
228
228
-5 .4 4
6 .97
1 9 .5 -2 0 .4
173
189
225
215
194
219
152
190
-5 .2 6
7.2 9
2 0 .5 -2 1 .4
203
232
232
-5 .4 5 7
7 .6 4
2 1 .5 -2 2 .4
175
214
226
290
241
233
255
-5 .5 5
7 .9 0
176
204
215
290
286
274
284
-5 .6 6
8 .4 1
157
,1 5 8
178
216
244
292
351
238
293
269
-5 .6 0 7
8 .6 9
162
217
303
217
300
-5 .7 1 5
8 .9 6
205
218
395
374
385
—5 . 9 6 5
9 .2 0
177
219
275
310
293
-5 .6 9
9.4 7
305
-5 .7 3
9 .6 4
201
221
1 6 .5 -1 7 .4
1 7 .5 -1 8 .4
151
198
202
2 3 .5 -2 4 .4
2 4 .5 -2 5 .4
2 5 .5 -2 6 .4
2 6 .5 -2 7 .4
2 7 .5 -2 8 .4
2 8 ,5 -2 9 .4
163
180
206
. 69
222
330
272
314
X2-Xj
E xpt.
No.
Time o f
m irro r
d isap ­
pearance
(se c .)
179
181
184
245
279
390
325
308
313
-5 .7 5 5
207
208
302
392
347
-5 .8 6
1 0 .1 9
159
180
182
185
210
303
445
290
455
35 2
369
-5 .9 3 2
1 0.41
3 2 .5 -3 3 .4
209
346
346
-5 .8 5
1 0.62
3 3 .5 -3 4 .4
183
18 6
433
345
389
-5 .9 7 5
1 0.80
211
246
413
412
413
-6 .0 2 7
1 1 .0 2
3 5 .5 -3 6 .4
212
430
430
-6 .0 7 4
1 1 .2 0
3 6 .5 -3 7 .4
213
474
474
-6 .1 7 3
11.42
2 9 ,5 -3 0 .4
3 0 .5 -3 1 .4
31. 5 -3 2 .4
3 4 .5 -3 5 .4
d
Ln A
»-L n d
z
9 .9 2
100
loo
I
■
p ig .
j
i
|
i
I
:
!
4 a - - D i s a p p e a r a n p e - o f <f r e e j - r a d i c a l s
o f p ro p ionaldehytfe
!
;
I
■
in photoiypi-a
I
I
■ ■
■
—j--------j
90
A - a c t i v it y ,o f free ra d ic a ls • l/(tim e of m irro rrem o v aL
z - timfc o f t r a n s p o r t o f v a p o r f r o m l a m p t o m i r r o r s .
6>0
so..
L—
SO
-i-4
F ig .
\
.oc
4 b --D isa p p ea ra n c e of fre e r a d ic a ls in p h o to ly s is of prop io n ald eh y d e
z . r t i m e o f t r a n s p o r t o f v a p o r b e t w e e n l a m p and, m i r r o r s .
A « a c t i v i t y of f r e e r a d i c a l s r l / ( t i m e of m irro r rem oval)
-4.5D
cn
-550
of
3 .8
to ly sis
value
w ere
6
,
-3
x 10
see.
for
free
of p ro p io n ald eh y d e,
of
the
h alf-life
For purposes
of
con du cted
each
12,
18,
at
24,
u n d erg o in g
30,
pressure,
source
th at
of eth y l
of
in
fig .
are
V (c a lcu la tio n s
The
agreem ent
is
w ith
the
of
aceto n e.
in
h alf-life
of
F ig .
same
pressure
of
rad icals
from
p h o to ly sis
observed
h alf-life
of th e se
com pares
fav o rab ly
w ith
the
value
of
The
one.
v alid
of
d isap p earan ce
th e
of
is
Tt
5 * 3 x 10 ° s e c *
is
,
lamp
concave
w hich
v alid
first
of
in
th e
order
and th e
x 10“ ® s e c .
5 .5
for
case
(m ethyl)
150,
4 .6
P a n e t h ’ s® f i g u r e
the
tim es
c alcu latio n
free
is
and l i g h t
31
also
of aceto n e
tem p er­
average
30
lam p:
vapor
from
in the
are
rad icals
the
g rad ien t,
P earson
V ia and V Ib show t h a t
the
P a n e th 's
from th e
The c u r v e
correct
w ere
as
d istan ce
III)*
p ro p ionaldehyde
of
pho­
m irro r ex p erim en ts
co n d itio n s
re su lts
th at
co n stan t
30
acetone
ag ain st
the
reactio n
and P e a r s o n 's
stan d ard
u sin g
tab le
the
th e o re tic ally
co n siaeratio n s
of
six
p ro p io n ald eh y d e.
p lo tted
the
ra d ical.
u n d er th e
for
in
fo llo w in g d is ta n c e s
a n d 36 c m . ,
w ere u s e d
m irro r rem oval
d irectio n
the
produced
good a g r e e m e n t w ith
vapor v e lo c ity ,
of
in
in
ra d ic als
com parison,
p h o to ly sis
atu re,
upw ard
the
T his
x 10"® s e c .
m ethyl
rad icals# .
ii TrT v i e w o f t h e l i m i t a t i o n s on t h e a c c u r a c y o f t h i s m e t h o d ,
th e low v a l u e f o r t h e h a l f - l i f e i s n o t a s e r i o u s e r r o r .
The
m ere f a c t t h a t th e h a l f - l i f e o f t h e r a d i c a l s from p r o p i o n a l ­
d ehyde i s m a rk e d ly s h o r t e r th a n t h a t o f th e r a d i c a l s from
a c e t o n e , i s s u f f i c i e n t t o e s t a b l i s h t h e i r i d e n t i t i e s a s tw o
d i f f e r e n t m o lecu lar frag m en ts.
Sam ple
and
the
calcu latio n s
a ctiv ity
and a c e to n e ,
of
the
startin g
for
free
w ith
d eterm in in g
the
rad icals
both p ro p io n ald eh y d e
the
-2 6 -
tim e
of
in
m irro r
tim e
of
rem oval
tran sp o rt
and
TABLE I I I
Free
Radical
i
C
C oncentrations
(Column h e a d i n g s
have
the
same
In
Photolysis
significance
of A cetone
as
lit Table
III
Xg-Xj
Expt.
No.
Ti me o f
m irror
disap­
pearance
5.5-6*4
248
251
269
278
285
95
56
70
97
85
92
83
-4.425
2.455
249
252
262
265
270
280
28 b
115
105
165
123
103
115
81
115
-4.751
4.68
250
253
266.
271
275
281
225
162
166
163
140
226
180
-5.20
6.69
254
257
267
272
282
287
216
207
224
205
238
196
214
-5.375
8.41
255
258
259
268
273
283
288
260
275
265
237
266
269
260
262
-5.579
9.92
256
260
275
276
28 4
289
265
337
343
353
335
368
337
-5 .8 3
261
11.5-12.4
17.5-18.4
23.5-24.4
29.5-30.4
35.5-36.4
d
Ln A
■-Ln d
z
1 1 .2 0
B)
S od
Fig.
S- - T i m e
of m irror
removal
in p h o to ly s is
d - time o f m i r r o r rem o v al
X g - 20| x d i s t a n c e o f m i r r o r
of acetone
fro m lamp e x i t
300
ZOO
2.00
100
loo
15"
10
30
__ --------- n -----------1----------------------------
J _ -----------.------------ r— -— ^ --------------------
P i g . 6.a-t--Dls.appear a n c e [ o f f r e . e r a d i c a l s
i n ! p h o t o l y s is o f acetone
i
!
j
!
I
J A. '“ j a c t i v i t y p f f r p e r a d i c a l ? • 1 / t t i m e o f m i r r o r ! r e m o j r a t )
a s ! t i m e o f t r a n s p o r t o f v a p o r fro m lamp e x i t t o m i r r p r
[
50-
40
20
m
9.
L-
;
■
j
i
—IOO
:
;
r
j
no
50
I
Fig.
6b—
A -
Disappearance
of acetone
activity
z s time
of f r e e
of
free
radicals
in p h o to ly sis
radicals
-l/(tim e of m irror
removal)
of t r a n s p o r t o f v a p o r fro m lamp e x i t t o
m irrors.
- 5.00
cn
-5.5b
-Loo
cn
distance
from
the
of comparison,
dehyde
Fig.
Table
BA.
straight-lines
obtained
for
photolyses
included
on o n e g r a p h ,
lamp,
the
and a c e t o n e
are
shown i n
are
For purposes
the
propional­
VII.
G*
The
Test
question
for
arose,
Photosensitization
during
m irror active
particles
i.e.,
through
the
vapor
on p r o p i o n a l d e h y d e
this
research,
were p r o d u c e d
interm ediate
through p h o to s e n s itiz a tio n ^ ® ,
action
and a c e t o n e
whether or n o t
of
excited
mercury
m olecules.
Cool
quartz
mercury arcs are k n o wn t o p r o d u c e mu c h r e s o n a n c e r a d i a t i o n
of
the
w a v e l e n g t h 2 5 3 7 %.
of
the
few l i n e s
of
causing
ular
to
the
electronic
The e x c i t e d
energy
of
decom position,
arc
excitation
liberates
w ithout
of
frequency
spectrum
molecule
a free
the
to
radical,
intervention
proceed
into
ultim ate
outset,
this
difficulty
one
capable
or resonance.
im part enough
break
the
whereas
of
is
which a re
mercury atoms,
might c o n c e iv a b ly
propionaldehyde
bond which
particular
mercury
m ercury atoms
the
m ight s t i l l
This
partic­
the d i r e c t
mercury vapor,
m olecules
in
the
prim ary
step.
At th e
the
apparatus
no q u a n t i t y
the
quartz
the
entry
the
rest
wa s d e s i g n e d
of mercury
tube.
vapor of any im portance
A trap
the
system .
sources
of m ercury v a p o r
and
sloping
were
the
i n s u c h a way t h a t
cooled
o f any v a u o r from
of
prevented
had been a n t i c i p a t e d
the
There
in
manometer.
by l i q u i d
it
is
ever
nitrogen
mercury d if f u s io n
were
the
system;
the
entered
prevented
pump i n t o
McLeod g u a g e
from b o th th e s e
the
tube,
-2 7 -
believed
t wo o t h e r p o s s i b l e
Vapors
from e n t e r i n g
and
quartz
sources
by me an s o f
Fig.
7--Com parison o f r a te a of d is a p p e a r a n c e :of a lk y l r a d i c a l s
i n th e p h o t o l y s e 3 qf a c e to n e and p ro p io n a ld e h y d e
A = a c t i v i t y of f r e e r a d i c a l s s l / ( t i m e o f m i r r o r rem o v al)
z r time o f t r a n s p o r t o f v a p o r from lamp e x i t to m i r r o r s .
O p e n c i r c l e s : r e s u l t s on p r o p i o n a l d e h y d e
Vv A O
S o l i d c i r c l e s : r e s u l t s on a c e to n e
O
2 * icf^ (sec.)
o
t u b e 0,
liquid
tered
filled
with
nitrogen.
into
silver
Thus,
an amalgam;
the Hanovia A lpine
propionaldehyde
lamp r e v e a l s
exact
value
the
tive
is
This
free
m irro r experim ents:
im ately
the
s a me
same d i s t a n c e
experim ent
that
the
second
iately
bing
at
2 5 3 7 ft,
radiation.
This
experim ent,
o u t by means
in
beneath
screen
using
dispersal
conditions
the
illum inated
w ith a i r
should
radiation
the
of
of
quartz
w ith
zone,
due
to
prevent
from th e
mercury a r c ,
the
the
in
lamp.
air
In
operation
three
antimony
in
4 cm.
Th e
approx­
at
the
first
o rd er to
the
show
In
light
was
of
the m e ta l
i mme d ­
that
a further
absor­
of any background
the
third
experim ent,
c o o l i n g wa s o m i t t e d
mercury vapor c lo u d .
any m ir ro r
therm al e f f e c t s .
order
passage
fre­
be e f f e c ­
m irrors
cooling,
hot
prim ary s te p .
of
in
the
not m atter here.
the
cooling,
with a i r
tube,
other
m irro r removal
m inutes,
also
the
the
exact re­
and hence
in
None o f
caused v a r ia tio n
in
the
in
this
two a t
the
at
are does
lamp,
radicals
means t h a t
energy
produced
resulted
r e m o v a l was n o t
in
f r e q u e n c y whould n o t
are
nine
free
has a b so rb ed
its
mercury a rc ,
spectrum o f
split
through mercury vapor over a pool
resonance
also
line
lamp i t s e l f
wa s p e r f o r m e d
the m irro r
filtered
the
was b o r n e
from the
w ide-tube
of
c a u s e d by t h i s
tim e,
was l i q u e f i e d .
An i n s p e c t i o n
resonance
all
mercury vapor en­
produce
radicals
supposition
it
a hot
other frequencies
in any p h o t o l y s i s
ray
to
the
the
3t
o th er end,
and r e d i s t r i b u t e d
that
re m o v a l means
any
E» c o o l e d w i t h
was u s e d
resonance
Y/hat t h e s e
The p o i n t
end,
and t r a p
confirm ation,
vapor.
frequency
quencies.
the
a v ery broad
of
one
Sun-Lamp,
mercury vapor w ith in
sonance
at
at
F o r more c o m p l e t e
turnings,
these
to
prevent
different
result.
40
DI SCUSSI ON
It
that
If
has
free
been
radicals
none had
been
been c o n s id e r e d
lysis,
of
shown
because
found,
the
of
the
in
the
w ithin
the
to
appropriate
As m a t t e r s
Paneth m irro r
after
the
the
case
would
is
case.
as
the
static
tisin g
first
erable
curve.
in
could
it
to
the
as,
hardly
indicate
breakage
full
expect any la rg e
alone,
which
to o b s e r v e
free
t h a t no m echanism
the
hope
pyrolysis
by B u r t o n ,
Positive
free
if
or
is
critical
energy
the
better
the
reveals
three
The
more
Furtherm ore,
an
its
w o u l d be
analogue,
-29-
B
^ in
is
at
in
to
the
least
the
the
present
acetaldehyde
half-life,
of propionaldehyde
distinct
interm ediate
than
for
reciprocal
pyrolysis
order,
up
1
such a case
process,
that
pressure
a second
in
evidence
than,
that
and Davis
mechanism
sole
The
the
of propionaldehyde,
results
radical
not
of u t i l i z i n g
R icci,
initial
length,
the
from th e
Failure
against
line.
for
have
and p y ro ­
from c o l l i s i o n s
transm it
propionaldehyde.
pressure:
order
one
propionaldehyde.
photolysis
n o t be a b s o r b e d
would
the
H inshelw ood3 s t a t e s
when p l o t t e d
of
mechanism c o u ld
activation
there
utilized
that
good
e x p e r im e n t a l work
bond..
mechanism,
of
of
the
pyrolysis.
acetalaenyde.
a com peting
time
the
m olecule
method
indicate
pyrolysis
in
the
photolysis
for
acquire
now s t a n d ,
method
of
energy
to
of
R ice-H erzfeId
both
photolysis
exists
the
the
mercury a r c ,
be n e c e s s a r y
radicals
resjults
bond c o u l d
number o f m o le c u le s
would
in
the
invalid,
if
the
aopear
a carbon-carbon
spectrum
in
segments
interm ediate,
section
expected
is
and
in
w ith
a
of c o n s id ­
from a t r a n s i t i o n
acetaldehyde,
exhibits
a
th re e “halves
Th e
by NO,
pyrolysis
and c a u s e s
hydrogen,
is
o rd er curve
than
no d i r e c t
of
the
free
radical
long chains
decompose
for
inhibited
of a c e ta ld e h y d e .
w ith n i t r i c
mechanism.
If
out
to u l t i m a t e
of
oxide
the
are
to
more
orto-
While
there
Yrfork o f M i t c h e l l
indicates
m olecules
that
at
least
decomposed v i a
a
com peting mechanisms c o - e x i s t ,
may be p r e s e n t .
that
is
long chains,
propionaldehyde
Suppose
very high p re s s u re s .
propionaldehyde
pyrolysis
evidence
24
to
a g re a ter conversion of p ara-
the
and Hinshelwood
half
of
up
This
may be
shown a s
e v e r y 51 a c t i v a t e d
m olecules
in
the
follow s:
m olecules,
prim ary
50
step:
C g H 5 C H 0 ---------- CgHg ¥ CO
and
the
other
one d e c o m p o s e s
into
free
radicals:
C g H p C N O ------------ Cr>U^ f H O C
followed
by
CgH sH C O
i- C p I l K ----------------- C ^ H g
C - H k C C --------------
C Hr
whereupon s t e p s
surrounding
(2)
and
molecules
(3)
until
a recom bination process,
SCgHg r
or
the
ethyl
the
molecules
anism*
repeat
the
(2)
radical
are
Minute
(2 )
CO
(3 )
and
reaction
rate
the
free
the
number t a k i n g
radical
radical
into
(3)
(4)
C? HPHOO
are
(5)
r e p e a t e d 50 tim e s
decomposed
by th e
free
by h a l f ,
instead
in th e
radical
-3 0 -
of
exclusive.
prim ary
before
then on e-half
o f NO w o u l d t h e r e f o r e
mechanism were
part
the
enters
M — — — C 4 H1 0 1* M
by c o l l i s i o n ,
only
upon
such as
disappears
amounts
the
them selves
ethyl
C2Hc r H C O
steps
f
*• C ^ H ^C C
O
i..
If
(1)
free
mech­
decrease
by 98$
if
The s m a l l e r
radical
process,
the
g r e a t e r must
be
the
chain
length
to
account fo r th is
observation,
Taylor
of
and
processes
Burton^"**
can
exist
low and
interm ediate
the
order,
3/2
be a c c o u n t e d
level,
to
for
followed
free
grees
the
to
in
have
since
at
to
activation
activation
initial
pressure
acetaldehyde
than
fact
that
the
acetaldehyde
comolex,
dehyde
and
w ill
transition
therefore
be m o r e
into
well
55b°K.,
for
acquiring
pressure
that
the
perm its
level.
36.5
ultim ate
in
to
case
of
oropionaldehyde
the
case
of
acetaldehyde;. a t
rises
kcal.
is
42
tran­
kcal.
It
rat#
However,
more c o m p l e x
also
about
be m o r e
of
propional—
the
forbidden
The i n t e r p r e t a t i o n
the
and
results
reaction
mus t be s o m e w h a t d i f f e r e n t
-3 1 -
decom­
from 5 6 . 0
5 0 0 mm.
w ill
bringing
This
a t 3 0 mm.
before
field
least
pro­
propionaldehyde,
molecule
m olecules.
the
energy
kcal.
a sm aller concentration
effective
de­
external fie ld s
that a first-o rd e r
propionaldehyde
means
electronic
energy hyporsurfaoe,
about
to 63.5
in
w h i c h may
by way o f a " f o r b i d d e n "
equally
at
of
the v i b r a t i o n a l
of m olecules
another
energy,
k cal.,
At
of p r e d i s s o c i a t i o n
of the
ener-y,
its
is
a higher
a higher electronic
reached w ith .in c re a s in g
the
to
opportunities
to
reaction
45.5
process
m olecules,
argument a p p lie s
from
is
activation
concentration
The
3 5 0 mm.
the
energy
presence
radiation)
excitation
differs
is
mo r e
and t h e
ultim ate
a lower n o t
where
of a c e t a ld e h y d e .
At h i g h e r p r e s s u r e s ,
larger
s i t i o n / wi t h o u t
w ithout
pressures,
by a s p o n t a n e o u s
from c o l l i s i o n s ,
position
pyrolysis
activation
radicals.
by t h e
in th e
by i n i t i a l
of freedom
vided
h a v e s hown how s u c h a c o m p e t i t i o n
in
from
mechanism c o m p e tin g
w ith
at
the
production
a relatively
th a t the
* '*
a change
low
in
the
the
numbers
compounds
enabled
compounds*
velocities
not
is
entirely
ma d e u n d e r
Fig.
of
m irror
disappearance
are
extrapolated
of
for
the
to
: *0179 s e c .
(when t h e
numbers
they
isom ers,
by c o l l i s i o n
of
the
two,
are
low.
at
is
i
- -1
free
to
t wo
and
tim e,
the
the
logarithm s
Since
of
they
the
photolyses
the
of
shows
the
and
time
from
values
.0169 sec.
the
in
“ 1
for
the
and a c e t o n e
should d isa p p e a r
same
rate
in
in chain
both acetone
the
the
experim ental
expressed
involved
that
of
3S •
lamp e x i t ,
s a me w i t h i n
are
but
half-lives
transport
the
two
and th e
t h a t when t h e
same t y p e
at
the
circum stance,
of
of
source),
between
propionaldehyde
are no t
room t e m p e r a t u r e s
Herr
tine
namely to
is
light
reciprocal
shows
a n d by w a l l r e a c t i o n
on t h e
the
that
a result
open to doubt.
fo r propionaldehyde
radicals
by
Th e two
pressures
w o u l d be
vapors,
natural
provided
and
fortunate
plotted
radicals
is
conditions
be ma d e
both the
against
represent.)
VVork p e r f o r m e d
aldehyde
of
caused
to e s ta b lis h
identical
A com parison of
aero
free
acetone
are
the
is
produced as
pressure,
o th er circum stances
lamp e x i t
error
identity
on w h i c h
reaction
appears
were
com parison
unexpected.
VII,
explanation
and p r o p i o n a l d e h y d e .
a remarkable
the
activity
radicals
tem perature,
first-order
process.
antimony m ir r o r s
a direct
become
An a l t e r n a t i v e
studbd under alm ost
The
must
a first-order
of acetone
were
radicals
chain-ending
(same v e l o c i t y ,
which
of
of fre e
photolyses
free
pressure.
occurrence
The work w i t h
equal
of
stream s
reactions.
and p r o p i o n —
quantum y i e l d s
and N o y e s 43 r e p o r t e d $ ( q u a n t u m y i e l d )
equals
0*49 a t
the
1 , 2 3 cm,
acetone
decreasing
photolysis
at
to 0*22 a t
room
1 6 * 3 cm* p r e s s u r e
tem perature.
Leighton
in
and
44
Blacet
, perform ing
dehyde,
found c o rre s p o n d in g ly
Instead
of
free
radicals,
were
obtained.
were
also,
s h o wn
to
above
th at free
number
however,
This
the
guard
This
H atoms
produtBd,
are
for
different.
It
present
ana
is
has
than
and a r e
of
the
radicals
already
been
demonstrate
Z% o f t h e
total
most p ro b a b ly
in agreement w ith p re v io u s
acetaldehyde^
that
the
experim ents
less
quantum y i e l d .
of disappearance
that
result
the
half-lives
indication
com prise
of
of
the
rates
m irror
particles
photolysis
to
an
h y u rogen atoms
absent.
o f w o rk on p r o p i o n a l ­
low v a l u e s
values
s o me e x t e n t ,
that
type
different
is
w o r k on t h e
up
same
identical
of a c t i v e
entirely
the
the
h Cq
which
radical
indicates
is
no
stable
o
IQw C.-fr
,^
•>:- M o l e c u l a r h y d r o g e n h a s b e e n f o u n d a mo ng t h e p r o d u c t s o f
o t h e r n h o to ly s e s of p r o p i o n a l d e h y d e :
See
B e r t h e l o t and G aud ech o n , Comptes R en d u s, 1 5 1 , 478,0-910)
L e i g h t o n and B l a c e t , J . A m . C h e m . S o c . , 54, 3X65, ( 1 9 3 2 )
W in k le r, F l e t c h e r , and H inshelw ood, P r o c . R oy.S oc.
144A .
345,
(1 9 3 4 ).
F a r k a s a n d S a c h s s e , Z« P h y s . C h e m . , B 2 7 , 1 1 1 , ( 1 9 3 4 )
F r a n k e n b u r g e r e t a l 3 , Z. E l e k t r o c h e m . , 3 6 , 7 5 7 , ( 1 9 3 0 )
b u t L e i g h t o n and B l a c e t ( l o c , c i t . ) a t t r i b u t e t h i s t o a s e c o n ­
d a r y r e a c t i o n i n th e R i c e - H e r z f e I d mechanism f o r th e decom­
p o s i t i o n of ald eh y d e s:
2 HCO
and B l a c e t a n d Volman
HCO
The o r i g i n a l
>
Hg
+ 2 CO
(J.Am.Chem.
* H2 +
RCH0
Rice-H erzfeId
HCO
Soc.
CO
mechanism
60,
1243,(1 9 3 8 ))
4> RCO
included,
first
3
ight,
it
as
a step
* H i CO
w h i c n h a s b e e n d r o p p e d by s u b s e q u e n t w o r k e r s i n
i s c o n t r a r y to t h e r e s u l t s of t h i s r e s e a i c h .
At
to
would a p p e a r
-3 3 -
that
the
the
field
half-life
and
of
3.8
“3
x 10
sec.
found
propionaldehyde
3.9
x 1 0 " ®,
radicals,
is
in
lower
evidence
close
conclusive
whereas
acetone,
is
,
fui t h e
the
than
of
a n d more
findings
o f P a n e t h and
half-life
of
the
ing d ia m e ter
Since
the
im ately
his
tube
difference
in
half-life
conditions
of
the
of the
that
to
results
If
such
This
of
conclusion
x
3 .8
10
—3
aldehyde
disappearance
hydrogen,
research)
to
x
is
10“ 3
ethyl
»
with
are
is
occurs.
fo u n d e d on a p p r o x ­
possible
the case,
the
increas­
disappearance
30
it
that
that
from a d i f f e r e n c e
suggests
sec.
for
in
a stream
wholly
different
wholly
fortuitous,
sec.
is
radicals#.
# a recalculation
m^ans of t h e i r
shows t h a t t h e
of t h e i r d a ta ,
calcu latio n is
that
the
-3
3 . 9 x 10
and the v a l u e of
37
and L a u t s c h
for ethyl ra d ic als
3 .8
of
the
in
the
in
the
the
geometry
conclusion
follow s
d e te r m in e d in t h i s r e s e a r c h would te n d
2Q
those of
Pearson*s
o r / p a n e t h and H o f e d i t z .
than
last
our value
in
the case
b a se d upon th e
increases
particularly
is
ethyl
half-lives
be l o w e r
their
2 5
is
6.36,37,38
in w hich the
experim ents,
apparatus.
the
radicals
same n u m b e r o f d a t a ,
in
of
of
or experim ental e rro r.
co-workers
of P earso n
figure
presence
sec.
from
b o t h P a n e t h and P e a r s o n ,
interpretation,
same f r e e
of th e
data
the
“3
x 10
of
resulting
with P a n e th 's
foi
of 4.6
figures
likely
experim ents
the
evidence
insufficient
A nother,
radicals
agreement
value
the
free
much h i g h e r
the
half-life
sec.
(which,
of d i l u t e
conditions
and
than
The o b v i o u s
agreem ent between
that
given
of p ro p io n by P a n e t h
incidentally,
lead
present
our conditions,
would c o r r e s p o n d
explanation
for
tetraethyl
from th e
for
is
is
that,
exclusively
if
37
the
o f th e v a l u e s of P a n e t h and L a u t s c h
by
r e v is e d formula f o r th e tim e of t r a n s p o r t
h a l f - l i f e o f e t h y l r a d i c a l , on t h e b a s i s
i s a l s o l o w e r t h a n 3 . 9 x 10
sec.
This
given in the appendix.
ratio
the
of
same
port
the
half-lives
provided
of
both
longer
of
the
that
(as
is
nalf-life
photolysis
free
w o u l d be
A more
of
the
radicals
ethyl
atoms
to
in
the
question.
point
of
transfer
strengths
the
radicals
The
ketores
discrete
s ome
in
all
range,
tional
bands.
region
at
for
same
45
spectra
but a ll
presence
the
nossess
CH3 ¥
the
and p ro p io n a ld e h y d e
concentrations
zone,
H err
cf
free
that
line
realm
and N o y es'^ ^ave
—3 5 ”
( i . e . , 2^ )
m agnitude.
of
free
methyl
to
resolve
the
m olecule.
of
to
producing
aldehydes
shows
absorb
are
VII
a definite
discretely
by r o t a ­
always
shows
that
illum inated
approxim ately
produced
presented
and
(P redissociation?)
sim ilarly
)
The b o n d
possibility.
absorption
Fig.
mechanism
in p ro p io n ald eh y d e
may be m a s k e d
and
the
interesting
saturated
2 5 3 7 ft.
radicals
this
a rupture
a continuous
w ave-lengths,
in th e
an
bonds
effect
acetone
rich
in
present
of
involves
believed
a ma xi mum^® n e a r 2 8 0 0 ft.
an arc
presents
formaldehyde
reaches
with
of
C H gC H O
insufficient
are
trans­
reaction
of t h e
are
the
present
be
the
so
Only
also
an e f f e c t
clearly
,
w ithin
although
shorter
it
for
rem ains
some p a r t i c l e s
for
problem
sim ilar.
All
is
used
possibly
carbon-carbon
seems
region,
might
radicals
T h e ma x i mu m c o n c e n t r a t i o n
a photo-activated
the
absorption
are
are
- ^ - ---------
the
two
approxim ately
methyl
in
of
radicals
be
here
speculation,
energy
are
presented
However,
for
then
possible
C H 3 C H 2 CHO
The e v i d e n c e
media a re
account
could
ethyl
here),
which
cause
formed
case
and
oropionalaeayde•
inadequate
orobable
sim ilar
than
hydrogen
of m ethyl
in
evidence
the
wh e n
(i.e.,
equal
irradiated
w hich suggests
( in view o f
with
mechanism.
it
increase
decreasing pressure,
photolysis
tion
the
by
acetone
If
acetone
follows
proceeds
of
that
of
the
among o t h e r
proceeds
we a s s u m e
Cg Hg / CO r a t i o
and
nrooionaldehyde
the
photolysis
exclusively
by a f r e e
3b—
of
at
via
products
that
the
a free
radical
the
same l i g h t
absorp-
the
wavelergths
used
propionaldehyde
radical
the
observations)
exclusively
approxim ately
in
mechanism.
also
46
,
SUMMARY
1.
of
Free
alkyl
radicals
propionaldehyde
life
of
with
the
value
of
free
ethyl
radicels.
for
2
the
by t h e
.
sim ilar
radicals
known
slightly
3.
lished
been
that
free
use
free
2#
of
that
free
w ith
of
sec.,
in
the
The
half-
good a g r e e m e n t
produced
x 10” ® s e c .
radicals,
as
photolysis
by P a n e t h and L a u t s c h
acetone
4.6
in
method.
given
by P e a r s o n
lead
the
com pletely
—3
sec.
methyl
the
5.3
guard-m irror
hydrogen
probably
free
Acetone
half-life
x 10“
of
sec.
3
is
under
atoms
total
of
absent.
formyl
certainly
number
photolysis
active
propionaldehyde,
is
result
stable
has
estab­
do n o t c o m p ris e
of m irro r
This
radical
technique
and
supports
up
to
particles
are
the
view
tem peratures
1 0 0 °C.
4
.
viscosity
used,
duce
It
the
m irror
x 10
—3
found
conditions.
cf
in
of
x 10
reported
produced
the
3.3
experim ents
different
The
than
3.9
is
been
Paneth
having a h a l f - l i f e
to produce
which has
more
particles
have
is
propionaldehyde
under
the
and
conditions
and u n d e P ^ c o n & r ti o n s
approxim ately
shown t h a t
acetone
equal
this
of
of
vapors
tem perature
illum ination
concentrations
m i g h t mean
-3 7 -
have
that
of
the
and
appear
alkyl
the
s a me
pressure
to
pro­
radicals.
photolysis
of
propionaldehyde
radical
5.
6
.
alm ost e x c lu s iv e ly
by a f r e e
mechanism.
The
possibility
may be c o m p e t i n g
tolysis
proceeds
cf
free
is
also
radical
discussed
that
decom positions
there
in the
pho­
nrcpionalaehyde.
The
experim ental
lysis
of propionaldehyde
sults
of
the
pyrolysis
evidence
obtained
may be u s e d
to
in the
explain
of propionaldehyde.
the
photo­
re­
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uhemische
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and B u r t o n ,
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282.
APPENDIX
It
error
is
in
believed
the
■27
i c a l ° f ; and
the
that
P a n e th and h i s
calculation
in
an
article
disappearance
m ir r o r method
in
of
free
of
38
the
in
h alf-life
which i t
radicals,
a sufficiently
co-workers
long
of
rad-
was m a i n t a i n e d
that
when s t u d i e d
tube,
is
than a f i r s t - o r d e r r e a c tio n . (Paneth,
38
Wunsch
p l o t t e d l o g A a g a i n s t z_ t o p r o d u c e
sults
It
is
on t h e
incorrect,
results
not
basis
and
the
of Paneth*s
1.
clear
his
01
just
w r ite r has
data
H alf-life
in
H ofeditz,
a curve,
arithm etic
therefore
these
of ethyl
v * 2125 cm ./s-ec.
a * . 0 1 7 mm. H g / c m .
Xau).
hi3
by t h e
of a higher
how P e i n e t h a r r i v e d
data;
in
ethyl
order
upward)*
the
were
at
and
concave
his
appears
recalculated
to
re­
be
the
two c a s e s .
r a d i c a l 37
(Paneth
p - 2 . 0 mm.
says .0017, but
uses
.017).
Assume f l a m e a t b e g i n n i n g o f t u b e .
C o n s i d e r t w o p o i n t s , Xo a n d X * c m . f r o m s t a r t .
X2 s 1 2 c m .
Xltr 0
X2 * ■ 2 8 c m .
d
— 40 s e c .
d* s 1 4 0 s e c *
In A s In
Ln A ’ s Ln
( 1 / d ) •* I n
( l / d ' ) s In
* 0 2 5 — —3 . b 9 5
.00714 - - 4 .9 b
z -
12
2125
-
. 0 1 7 x 12 2
2 X 2125 X 2 .0
tt . 0 0 5 3 6
Z* -
28
2125“
-
. 0 1 7 x 282
2 x 2125 x 2 .0
-
ti r
(b)
( l n 2 ) (z. - z* ) s
l n A* - I n A
. 693 ( * 0 Q 5 3 6 - . Q l l b 2 ) m . 0 0 3 4
-4 .9 b * 3.695
A s s u m e f l a m e 15 c m . f r o m
zone, ( v , £ , and a th e
( a a n d A* a l s o
rem ain
Xg a 2 7 c m .
^2** ^
z r
zt
27 - 15
2125 ’
- 4 3 -____
15
"*
2125
a Z --n
L« A -
.01162
b e g in n in g of c o n s t r i c t e d
same as b e f o r e ) .
thesame).
om*
®^
cm*
- , 0 1 7 ( 2 7 2 - 1 5 2_)_
2 x 2 1 2 5 X 2 .(5
-
. 0 1 7 (, 44 /3 - 1 5 )
2 X 2!: 1 2 5 x 2 . 0
- .00464
- .00992
~ z<> r , 6 9 3 ( . 0 0 4 6 4 Ln A*
-41-
sec.
-4.96
f
.00992)
3.965
«. . 0 0 2 9
sec.
E ither re su lt
value
of
g0059
th e ir paper,
ticles
(the
of h a l f - l i f e
Order of
values
is
*0038 s e c .
in
reality
to
of
yield
observed
in a l l
radicals
(fig.
8
that
first
order reaction
the
of
flame
before
it;
the curve
iably
a siraight
the
is
at
if
the
line
).
It
length
the
be
is
beginning
and
they are
give
25
(25 -
42
(42 -
5,9
(59
78
(78
95
(95 -
115
(115
133
(133
-
as
slightly
to
It
of
constricted
is
believe
assumed
downward,
z(P anethf s)
100/340)/1035
* .00938
525/340)/1035
• .0224
1764/340)/1035
- .035o
3490/340)/1035
- .0471
6090/340/1035
- .0581
9025/340)/1035
— .Ob6 l
- 13200/340)/1035
- .0737
-"17700/340)/1035
» .0782
-4 2 -
that
be m a i n t a i n e d r e ­
tube.
concave
the
of free
that
tube or
anywhere dow nstream from t h i s
z. ( w r i t e r ' s )
-
compared
a ourve,
same n a t u r e
w ill
of
f r o m P a n e t h 1s
d i f f e r e n t from a s t r a i g h t l i n e .
v r 1035 c m . / s e c .
a/p -
(10
calculation
reasonable
the
par­
of m ethyl r a d i c a l s ^9
determ inations
rate
the
research
in h is
results
therefore
of the
the
o f CH3 a n d C g H^ .
w riter
of the
other h a lf - li f e
located
w ill
X2(cm.)
10
in e r r o r
of
that
in th is
transport),
calculations
lower than
belief
a mixture
be
w rite r's
gardless
the
found
W h i l e P a n e t h 1s c a l c u l a t e d
the
is
re a c tio n o f recom bination
z (tim e
the
sec.)
by P a n e th and L a u ts c h in
w eight to
believed
of
below w ith
data.
are
.0029
presented
and le n d s
Paneth
the
sec*
w riter* s)
2,
(.0034 o r
point,
but not apprec­
1/170
d(seo. )
AslO4
d
Log A
«00 b8
190
5 2 . b3
*1.721
.0175
360
27.78
1.443
.0300
600
16.67
1 .2 2 2
.0431
900
1 1 .1 1
1. 0 *6
.0584
1500
6.67
0.824
.0727
2040
4.90
0.690
.0901
2820
3.55
0.550
.1 0 6 8
3600
2 .7 8
0.444
•IH
Cl
£X
■H
P
O
a) co
c>
cd to
O tO
u to
D.
< n Ch
0)
<M r-H
0D
to o
O ffi
r-t 0)
>>.c
si o
E *-a
Cm
o x;
P
rC
CU O
u rn
3
<u g
t
H <m
I 1 O
p
cd
bO cd
«-t
tj
n
to o
CP
I* to
to P
«T*
oJ
The s l o p e
Since
decadie
and t i
life
ca,
-
of
the
logarithm s
, 6 9 3 / k ~ ,0 1 5 5
of methyl r a d i c a l
,005
straight
sec.
in
are
used,
sec,,
in
a 5 mm,
a
line
in f i g ,
k z 2,303
which a p p e a r s
10
mm,
tube.
L ] ) i k -i k v
V- V. L’ntv.
tube,
as
8 is
19,3,
x 19,3
to
s
be t h e
44,2
half-
compared w ith
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