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International Symposium on Thermal Analysis.

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pounds of the naphthalene dianion and two [AIEt2]+ or two
[TH F-AIEt21"
cations and not derivatives of dihydronaphthalene. They can be only slightly dissociated, however,
for the specific conductance of a 0.5 M solution of the T H F
~
ohm-I/cm at 2OoC,
adduct of (3) in T H F is 1 . 3 10-5
whereas that of a 0.5 M solution of ( I ) is I. I x 10-3 ohm-l/cm.
Compounds corresponding to the T H F adduct of (3) can be
obtained by dehalogenation of EtZAICI o r EtAIC12 with
solutions of alkali metal arenes ( e . g . anthracenesodium or
naphthalenelithium) in ethers (e.g. T H F or dimethyl ether).
The T H F adduct of bisdiethylaluminobiphenyl obtained
from sodium biphenyl and E t 2 A I C k T H F decomposes at
2OoC/15 mm with release of biphenyl. A free EtZAIG-THF
radical, which becomes stabilized by disproportionation t o
form aluminum, T H F , and E t 3 A l t T H F , is formed as an
intermediate in this reaction.
Received: May 25th, 1965
[Z 9921818 1El
German version: Angew. Chem. 77, 623 (1965)
~~
..
oxide according t o Koenigs and Knorr [4]. The trimethylsily
groups can then be removed with a mixture of methanol
water, and glacial acetic acid (20:20: 1 v/v) at room temperature. The excess 2.4-dinitrophenol is separated by
chromatography on silica gel with benzene as eluant. The
2,4-dinitrophenyl glycoside is then eluted with ethyl acetate.
The anomers of the 2,4-dinitrophenyl glycosides can be
separated by thin-layer chromatography with benzene/
methanol (2: 1 v/v) as solvent or by column chromatography
o n silica gel with ethyl acetate as eluant.
2.4-Dinitrophenyl
glycoside
1-D-Galactoside
8-D-Galactoside
P-D-Glucoside [bl
?-D-Mannoside
a-L-Arabinoside
[j-L-Arabinoside
-~
[I] Experimental work i n collaboration with H. Nehl.
Synthesis of 2,CDinitrophenyl
13-0-Glycosides
M-
1
M. p. ['Cl
(decomp.)
I
Yield
"73 [a]
158
150- I 5 1
10O-lO1
I49
I67
I58
10
28
i
I
32
I
rglZ,L
i 322 ", c
-105 ', c
-92.8 ",c =
t 161 c =
- 103 c .
- t 3 6 7 ', c =
'.
O,
0.66 [cl
1.0 [cl
1.06 [c]
1.0 [c]
1.05 [dl
0.96 [dl
[a] Based on the amount of ethyl thioglycoside taken.
[bl Crystals contain 1 mole of acetone.
[c] I n methanol.
[d] In dimethylformamide.
and
By Dipl.-Chem. W. Hengstenberg and Prof. Dr. K. Wallenfels
Chemisches Laboratorium
der Universitat Freiburg/Breisgau (Germany)
2,4-Dinitrophenyl glycosides were previously known only in
the form of acetylated derivatives [ l ] since the very labile
2,4-dinitrophenyl-O-glycosidicbond cannot withstand acidic
or basic deacetylation.
We have prepared free 2,4-dinitrophenyl glycosides in the
following manner. Ethyl thioglycosides are protected according to Bently et al. (21 with a trimethylsilyl group, which
is easy t o remove by hydrolysis. The ethylthio residue is then
replaced by a bromo substituent by treatment of the protected glycosides with bromine in carbon tetrachloride [3]. The
sirupy trimethylsilylated bromohexose obtained is converted into the glycoside of 2,4-dinitrophenol with silver
2,4-Dintitrophenyl Ij-D-galactoside and 2,4-dinitrophenyl aL-arabinoside are both split rapidly by the @-galactosidase
from Escherichia coli. 2,4-Dinitrophenyl Ij-D-giucoside is also
a substrate - albeit a very poor one - for this crystalline
Ij-galactosidase. 2,4-Dinitrophenyl a-D-galactoside is a substrate only of the a-galactosidase from coffee beans. Dilute
alkali hydrolyses all the glycosides listed in the table.
Received: May 31st. 1965
[Z 9931821 IEI
German version: Angew. Chem. 77, 623 (1965)
~.
[ I ] H . G. Latham, 1. R . E. L . May, and E. Mosettig, J . org.
Chemistry IS, 884 (1950).
[2] C. C. Sweeley, R . Bentley, M . Mnkita, and W . W . Wells,
J. Amer. chem. SOC.85, 2497 (1963).
[ 3 ] W. A. Bonner, J. Amer. chem. SOC.70, 770, 3491 (1948);
F. Weygand and H . Ziemnnn, Liebigs Ann. Chem. 657,179 (1962).
[4] W. Koenigs and E. Knorr, Ber. dtsch. chem. Ges. 34, 957
(1901).
CONFERENCE REPORTS
International Symposium on Thermal Analysis
On April 13th and 14th, 1965, the Chemistry Department
of the Northern Polytechnic in London (England) arranged
a Symposium on Thermal Analysis.
F r o m t h e lectures:
Differential Thermal Analysis of Polymer Dissolution
D. A . Blackadder and H . M . Schleinitz, Cambridge (England)
Polyethylene precipitated from a dilute solution crystallizes
in thin diamond-shaped lamellae whose thickness increases
regularly with temperature of crystallisation. Annealing crystals in a solvent at a temperature between the crystallization
and melting temperatures causes partial dissolution starting
at the crystal edges and subsequent reprecipitation o n the
same sites at a thickness characteristic of the annealing temperature. The melting or dissolution temperature is dependent
upon the thickness and consequently upon the thermal history
of the crystals.
Differential thermal analysis at low heating rates was
applied to suspensions of polyethylene single crystals in
Angew. Cliern. internat. Edit.
/
Vol. 4 (1965)
I No. 7
various solvents. The melting point of the crystals increases
monotonically with the temperature of crystallization. It was
found that crystals prepared at lower temperatures anneal to
a greater extent and at a greater rate than those prepared at
higher temperatures. Samples annealed for short times showed a multiplicity of peaks characteristic of both the original
crystallization temperature and the annealing temperature.
The implication is that under annealing conditions the crystals d o not thicken regularly. Either some crystals thicken as
expected and others not at all, or else only parts of each crystal thicken. Electron microscopy revealed that the latter
interpretation is correct.
Simultaneous Thermogravimetric and Differential
T h e r m a l Analysis of the Decomposition of C h r o m a t e s
and D i c h r o m a t e s
E. L. Clinrlsley and J . P . Redfern, London (England)
Thermal decompositions can be studied by thermogravimetric analysis (TGA), but the results often must be supplemented with other data, notably from differential thermal analysis
60 1
(DTA). Correlation of the two sets of data often is difficult,
since the instruments used normally d o not employ the same
experimental conditions. A Stanton HT-D thermobalance
was therefore modified to enable simultaneous DTA and TGA
measurements to be made.
With this instrument, the thermal decompositions of numerous chromates and dichromates were investigated, where the
following reactions occur (among others):
MxCr04.n H20 (s) + M ~ C r 0 4(s)
[x = 1 or 21
+ n H20 (9)
An acetamido group in the meta position of styrene increases
the thermal stability of the resultant homopolymers (4) and (5)
to a lesser degree than an amino group does, whereas the acetylated copolymer (6) has a thermal stability similar to that of
the acetylated homopolymers (4)and (5) but shows enhanced
thermal stability over the amino copolymer (3). The molecular weight apparently has no effect upon the thermal stability.
On pyrolysis in nitrogen, practically n o difference was found
for the polymers ( I ) , ( 5 ) , and (6) from the pyrolysis in air.
(1)
Thermogravimetric Analysis of Oxides
This reaction may be multi-stage.
H . Uwenfs, Drogenlos (Belgium)
MxCr04 (s)
+
2 MxCr04 ( s )
+ 2 MxOCrzO3 (s)
MxCr04 (1)
2 MxO-Crz03(s) +
2 MxO-Cr203(s) +
(24
+ 3/2 0 2 (g)
MxOCr203 (s) + MxO (s)
2 MxO (s) + Cr203 (s)
(2b)
(3a)
(3b)
These reactions may be simultaneous to or even precede
reaction 2(b)
MIIOCrrO3 (s)
+ MO (s)
- + M2ICr204 (s)
+ 1/2 0 2 (g)
(4)
Thermal Analysis of Inorganic Azides
H . Rosenwasser and 0.F. Kezer, Fort Belvoir, Virginia (U.S.A.)
The reaction of rare earth sesquioxides with hydrazoic acid
yields basic azides. These compounds containing the elements
from lanthanum through dysprosium in the lanthanide series
have a metal to nitrogen ratio of 1 : 6 and may be formulated
as Ln(0H) (N3)2.1.5 H20, whereas the heavier lanthanide elements (and yttrium) formcompounds with lower azidecontents,
which fit the formula L ~ z ( O H ) ~ N ~ . HInfrared
~O.
spectra,
however, indicate that the compounds have a n 0x0-structure.
These compounds were studied by means of differential thermal analysis. In general, the thermograms show the endothermic peaks caused by loss of water, and exothermic peaks due
to the conversion of azide groups to nitrogen molecules. Both
processes sometimes occur simultaneously. From thermogravimetric analyses, an oxyazide and an oxyhydroxide are
postulated as intermediates in the decompositions.
Although the thermal decomposition of the basic azides of
lanthanum and praseodymium proceeds smoothly in air, the
reactions taking place in vacuum often lead to explosions.
Studies with a DuPont micro-DTA unit show the effect of
heating rate as a factor in determining whether or not the
samples will explode. Information recorded on the thermograms includes crystalline phase transitions, melting points,
and decomposition of the azide ions. In the case of thallium
azide, a crystal structure change has been indicated for the
first time.
Thermal Analysis of Poly-(m-Aminostyrene) and
Related Polymers
R . H. Still and C. J . Keuttcli, Hatfield and Boreham Wood
(England)
m-Aminostyrene was homopolymerized using two different
concentrations of cc,a’-azobisisobutyronitrileto yield two homopolymers ( I ) and (2) of differing molecular weight. Copolymerization with styrene yielded a 2:1 copolymer (3) (2 moles
styrene : 1 mole m-aminostyrene). Acetylation of these polymers yielded poly-(m-acetamidostyrene) (4) and ( 5 ) , and the
corresponding 2:l copolymer (6). These substances were
studied by TGA in static air. The homopolymers ( I ) and (2),
owing to the presence of amino groups, are thermally more
stable than polystyrene, but the copolymer ( 3 ) showed no
enhanced thermal stability.
602
The reduction of simple oxides in a hydrogen atmosphere or
hydrogen stream using a thermobalance allows their stoichiometry to be determined.
This method was extended to mixtures of a non-volatile
(AmO,) and a volatile (BnOy) oxide. After preparation under
conditions (calcination at high temperature) where partial
evaporation of the volatile compound could be expected, the
composition of the final product was determined by the following procedure: The weight loss on reduction gave the total
amount of oxygen bound in the mixture. From the weight of
the residue the total quantity of metal (A+B) became known.
In a separate run the volatile oxide BnOy was evaporated at
high temperature under vacuum. The subsequent reduction of
the residue gave the amount of the metal A. The quantity of
the metal B was calculated by difference.
When the oxides form a solid compound (ApBqO,), a n excess of the volatile oxide can be removed at high temperature
and atmospheric pressure. Subsequent reduction of the residue
gives the amount of the combined metallic components
(ApBq). The oxygen content of the combination ApBqO, is
obtalned by the weight loss during reduction. Finally the
amount of component A is determined as decribed above.
German version: Angew.
[VB 922/229 IE]
Chem. 77, 592 (1965)
Microanalytical Redox Titrations
J . Z$ka, Prague (Czechoslovakia)
Suitable solutions for redox microtitrations include lead(1V)
acetate in glacial acetic as an oxidizing agent and hydrazine
sulfate or hydroquinone as reducing agents. The redox
potentials of other solutions can be shifted by combining the
oxidized or reduced form of the reagent in a complex or
sparingly soluble product. Examples of this are titrations
with iron(I1) sulfate in triethanolamine [l]. Under alkaline
conditions and in the presence of triethanolamine, iron(I1)
sulfate is a strong reducing agent. Compounds of trivalent
manganese, copper(I1) and bismuth(II1) salts, as well as
dichromates and tellurates can be titrated directly. The
titration of dichromate by this method is more sensitive
than in acid solution. It is suitable for the microdetermination
of dichromate in the presence of vanadate(V) which is not
reduced under these conditions. Tellurates can be determined
in the presence of tellurites and compounds of four- and
six-valent selenium. The method can also be used for the
potentiometric microdetermination of aromatic nitro groups
(reduction to NHz groups) and of nitroso and azo compounds.
[Osterreichische Gesellschaft fur Mikrochemie und
Analytische Chemie, Leoben (Austria),
January 29th and 30th, 19651
[VB 912p20 IEJ
German version: Angew. Chem. 77, 626 (1965)
[ I ] J . Doleial, E. Lukfyte, V . RybaCek, and J. Z+ka, Coll. czechoslov. chem. Commun. 29, 2597 (1964).
Angew. Chem. internat. Edit. 1 Vol. 4 (1965) 1 NO. 7
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