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Detection of Mesomeric Limiting Structures by Electron Spin Resonance.

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C O N F E R E N C E REPORTS
Cross-Linked Polymers from
x , x'-p-Phenylenediacrylonitrile
larger amounts of or-cyanostyrene ( 4 ) were identified by
hydrogenation, IR spectra, and formation of the dimer.
By W. Funkel*]
Lecture at the Chemischen Werken Huls A.-G., Marl (Germany)
IVB 48 IE]
o n December 7th. 1966
German version: Angew. Chem. 79, 624 (1967)
p-Phenylenediacetonitrile reacts with formaldehyde (molar
ratio 1:2) in a homogeneous medium (nitrile 0.128 mmole
per ml of CH30H; CH30Na 0.57 mole per mole of nitrile;
ca. 65 OC; 1 h) as well as in heterogeneous medium (nitrile
0.04 mmole per ml o f H20; NaOH 0.22 mole per mole of
nitrile; 60-100 'C; 1 h), yielding or&'-p-phenylenediacrylonitrile which, however, like the or-cyanostyrene that arises
from phenylacetonitrile and formaldehyde, cannot be
isolated because it immediately polymerises anionically [I].
Unlike the products formed in a homogeneous medium, the
cross-linked polymers of a,a'-p-phenylenediacrylonitrilethat
are obtained from a heterogeneous medium contain only
?CH and -CH20H as end-groups, so that quantitative
determination of the end-groups and study of the initiation
and termination steps would appear to be simpler. Nevertheless, quantitative analysis of the end-groups is not completely satisfactory for the cross-linked polymers, so that the
end-groups were investigated for the linear polymers (5)
prepared from phenylacetonitrile and formaldehyde via
a-cyanostyrene. It has been shown earlier that, for reactions
in a homogeneous medium, these linear polymers are good
models for the cross-linked polymers.
The hydroxymethyl end-groups were determined by titration
with phenyl isocyanate and by nuclear resonance spectroscopy. The ratio of hydroxymethyl to phenyl groups was
calculated from the oxygen and nitrogen contents. The ratio
of >CH to phenyl groups was evaluated by nuclear resonance
spectroscopy. In this way the fCH/CHzOH ratio was found
to be 2.7 to 3.0, whence it is concluded that the phenylacetonitrile anion is the preferred initiator for anionic polymerization of the intermediate monomer, even in the presence
of water, and that addition of a proton to the anionic end of
the chain in a termination reaction is not the only way in
which the >CH end-groups are formed.
CN
[*I Doz. Dr. W. Funke
Forschungsinstitut fur Pigmente und Lacke e.V.
WiederholdstraBe l0jl
7 Stuttgart N (Germany)
[l] W. Funke, Makromolekulare Chem. 93, 33 (1966).
Detection of Mesomeric Limiting Structures by
Electron Spin Resonance
By H. B. Stegmann and K . Schefler[*l
4-Amino-2,6-di-t-butylphenolscan be converted into stable
paramagnetic compounds by oxidation with alkaline ferricyanide solution or by heavy-metal oxides in solvents such
as alcohols, ether, benzene, or pyridine.
:0:
R = H, CH3, CH(CH3)2, CsH5
In the ESR spectra of these radicals, a hyperfine structure is
recognizable that is to be attributed to interaction of the
unpaired electron with the nitrogen, as well as with the
protons of the amino group and of the substituent R. This
indicates that in descriptions of such systems, in addition to
the usual mesomeric limiting structures of aroxyls, structures
must be considered in which there is an appreciable spin
density at the nitrogen atom.
CN
~6- C H ~ O H
H O C H , - ~- C H ~ O H
CN
Excess C,H,-CH,CN
I
?=cH,
1
~
0
(4)
\
I
Excess C H z O
I
C,H,-CH,CN
(3), R
=
CHzOH
:CH,O= 1 : I
When a large excess of formaldehyde (molar ratio 1O:l) was
used in a heterogeneous medium at 64 " C , or+-bis(hydroxymethy1)phenylacetonitrile ( I ) was isolated, and dimeric
or-cyanostyrene (2) and its formaldehyde adduct (3) were
identified. When a shorter reaction time (10 min) was used,
Angew. Chem. internal. Edit. / Vol. 6 (1967) / N o . 7
The hyperfine structure is very strongly dependent on
temperature; this can be ascribed to a decrease in the nitrogen
coupling constant U N and in the splitting of the amino-proton
coupling constant UNH with increasing temperature. The
temperature-dependence of both coupling constants is linear
between 200 and 500°K and when R = H the gradients are
-13 mG/'K for UNH and -1.3 mG/'K for U N . The
relationships can be best described, qualitatively, by a model
in which the amino group carries out hindered rotation
bond. The hindering potential is
around the Caro,.-N
derived, not from the steric situation, but from the gain in
delocalization energy connected with the orientation of the
molecule at low temperatures.
639
In experimental study of 4-amino-2,5-di-t-butylphenoxyl,
qualitatively and quantitatively the same temperaturedependence for nitrogen and amino-protons was observed
even though the steric environment had been considerably
altered. Further, an increase in spin density in the aroxyl
ring can be assumed from the increase, with temperature, of
the coupling parameters of the proton in position 6. Thus
aminoaroxyls can be described as mesomeric radicals in
which limiting structures that account for free electron
density on the nitrogen contribute a considerable part,
although with rising temperature these limiting forms
decrease significantly in favor of “aroxyl structures”.
Lecture at Isny/Allgau on January 25th, 1967
[VB 62 IE1
German version: Angew. Chem. 79, 625 (1967)
[*] Dr. H. B. Stegmann and Dr. K. Scheffler
Chemisches Institut der Universitat
Wilhelrnstr. 33
74 Tiibingen (Germany)
The stationary states brought about by active transport are a
special case of the dynamic states characteristic of life.
There is a further special case when organic compounds
occur in organisms in stationary concentrations that surpass
those given by equilibria; an example is the coexistence of
serum albumin with the amino acids of which it is composed.
Supply of free energy (for albumin by way of adenosine
triphosphate) is necessary also for preservation of these
dynamic conditions.
Since work is required for the maintainance of stationary
states, even in conditions of strongly depressed life activity,
we have measured the respiration of spores of Baciflus
cereus. It corresponded (in water at 30°C) to a half-life for
“self consumption” of several hundred years, and was smaller
by powers of ten than the respiration of the vegitative forms.
At 19°C or in the dry condition, the respiration of the
spores was immeasurably small, but it was much increased
by exogenous glucose or dinitrophenol. It is possible that
on further improvement of the sensitivity of the radiochemical methods an energy metabolism can be demonstrated
in all cryptobiotic systems.
Active Transport of Ions through Biogenic
Membranes
Colloquium at Berlin-Dahlem (Germany)
on February 7th, 1967
[VB 68 IE]
German version: Angew. Chem. 79, 624 (1967)
By E. Broda *I
[*I Prof. Dr. E. Broda
Active transport is the movement of a solute against the
gradient of the electrochemical potential; it is observed only
at biogenic membranes. For instance, NaCl is enriched on
the inner side of surviving frog skin; thus separation occurs
if an NaCl solution is divided by a frog skin. Experiments
with other salts, and in particular experiments by Ussing and
Zerahn’s “short circuit” method [*I, have shown that, in the
frog skin, active transport is specific for sodium - the counterion follows the resulting potential difference. According
to Ussing the electrical potential between the two sides of
frog skin first observed by DuBois-Reymond in 1848 is to be
ascribed to active transport.
Active transport increases the total free energy of the solutions separated by the membrane, and decreases their
entropy. Clearly a compensating decrease in free energy and
increase in entropy results from metabolic processes in the
membrane. Presumably it is adenosine triphosphate formed
in metabolism that drives the “ion pump”, and its efficiency
IS found to be considerable (ca. one half). The unknown
endogenous substrate can be replaced experimentally by a
defined exogenous substrate (radioglucose). The C02
formed can be measured with a gas counter and a consumption of 10-12 mole cm-2 h-1 can be determined. The
share of the glucose in transport work, as found experimentally, can be represented over five powers of ten in
glucose concentration by a mechanism according to which
glucose-6-phosphate resulting from hexokinase reaction
competes with endogenous (non-radioactive) glucose-6phosphate.
Apparently all biogenic membranes are capable of specific
active transport of some substance or other (even neutral
molecules), and by participation of “passive” diffusion in
the opposite direction this leads finally to a stationary state.
Radiochemical experiments with ChforeIIu algae show that
the energy for transport of potassium (uptake from the
nutrient solution) is made available either by respiration or
by illumination (photophosphorylation). The mechanism for
transport of potassium is largely specific for that element
(and for rubidium). Bromide is also subject to active transport
by the algae; the bromide transport system can also bring
chloride into the interior of the cells, but not other anions.
It is at present not clear why glucose inhibits active transport
of bromide; this is not due to an osmotic effect since galactose and mannitol are ineffective. Trace elements also, e x .
zinc, can be enriched actively by algae. However, proof is
more difficult with polyvalent cations as these are also taken
up strongly by ion exchange, i.e. a passive process.
6 40
Institut fur Physikalische Chernie der Universitat
Wahringerstr. 42
Wien IX (Austria)
[l] H . H. Ussing and K . Zerahn, Acta physiol. scand. 23, 110
(1951).
A New Class of Lewis Acids
By F. WesseIy[*J
Condensation products from cyclic malonyl acylals ( I ) and
aldehydes or open-chain or cyclic ketones can be titrated as
monoprotic acids. Chemical and physicochemical measurements as well as quantum mechanical calculation (after
Polansky et af.) show that an HOO or alkoxide ion B”
is attached to the (3-carbon atom with formation of the
anion (2), which is stabilized by delocalization of the
negative charge.
0
0
6
(1)
Q
(2)
The evidence is :
la) In most cases, e.g. R = H, R1 = alkyl or aryl, compound
( I ) yields no CH4 with the Zerewitinoff reagent.
lb) Formation of compound (3) is proved by degradation
reactions.
0
lc) Alkaline solutions of compounds ( I ) cannot be catalytically hydrogenated.
2a) Compounds ( I ) in neutral solution give a UV spectrum
that changes characteristically when the anion is formed in
alkaline solution. A band is formed that is peculiar to the
anion (5) of Meldrum’s acid (4).This anion is also stabilized
by delocalization of the negative charge.
Angew. Chem. internat. Edit.
Vol. 6 (1967) 1 No. 7
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