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Autoxidation of Polyepoxides.

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amount of material that resists desorption depends on the
temperature, solvent, and pigment and, above a certain
concentration, is independent of the amount adsorbed. After
adsorption of acid the amount resisting desorption is greater
the more basic the pigment. It must thus be assumed that at
least part of the non-desorbable acid is bound chemically to
the pigment surface.
Reactive compounds do not lose their reactivity when firmly
bound to the surface. For instance, the acrylic or methacrylic
acid that cannot be desorbed from titanium dioxide (rutile)
copolymerizes with styrene. The polymer, which is firmly
bound to the pigment surface by its carboxyl groups, was
identified by elemental analysis and IR spectroscopy.
Lecture at Freudenstadt (Germany), Sept. 29th 1966 IVB 26b IEI
German version: Angew. Chem. 79, 192 (1967)
Autoxidation of Polyepoxides
were subjected in undiluted form to autoxidation in air as
well as in oxygen at temperatures from 50 to 1.50 OC and for
times from a few minutes to several hours. Degradation of
the substituted polyethylene oxides sets in at once (recognizable by a loss in weight), with simultaneous decrease
in the molecular weight (observable as a decrease in solution
viscosity); cross-linking does not occur. Only small amounts
of volatile products are formed from polyethylene oxide and
there is barely any decrease in molecular weight; degradation
occurs at higher temperatures (ca. 145 “C) than for the
substituted polymers.
The volatile products were identified by gas chromatography.
The first to volatilize from substituted polyethylene oxides
are the alcohols ROH derived from the substituent R, the
methyl ketones R-CO-CH3 isomeric with the monomer,
and the secondary alcohol R-CHOH-CH3
formally
derivable from these by reduction. Water was the only
volatile product observed to be formed from polyethylene
oxide.
The mechanism of the oxidation with molecular oxygen can
be interpreted as formation and decomposition of ether
hydroperoxides in the first step:
L. Dulog, Maim (Germany)
Substituted polyethylene oxides of the general formula
(-CHz-CHR-O-),
have been prepared from the monomers by use of modified organometallic catalysts, such as
partly hydrolysed aluminum alkyls subsequently treated
with acetylacetone. In each case the polymers have been
separated by solvent-extraction, e.g. with ether or acetone,
into a tactic and an atactic fraction. The difficultly soluble or
insoluble fractions are the isotactic ones according to X-ray
diffraction and I R spectra. This is in agreement with literature
data.
Isotactic polypropylene oxide, isotactic poly-1-butene oxide,
and isotactic polystyrene oxide, as well as polyethylene oxide
7
.--CH,-C-O-);..
/
?OH
...(-CH,-C -O-),...
i ROH
I
R
t+
\
01
...( -CH2- YH-O-)n...
R
o r cleavage of
bonds in polymer
chain
Lecture at Freudenstadt on September 29th and 30th, 1966 [VB 26c IE]
German version: Angew. Chem. 79, 192 (1967)
Symposium on Heterocyclic Chemistry
The Institut fur Organische Chemie of the Technische Hochschule Stuttgart (Germany) was host to the 1st German
Symposium on Heterocyclic Chemistry from the 5th to the
7th of October, 1966.
R2
l*R
1
@
(3)
F r o m t h e lectures:
The Aromatic Character of Six-Membered Ring Chelates
E. Daltrozzo and K. Feldmann, Munich (Germany)
Compounds of type ( I ) can form hydrogen-bridged chelates
(2) containing a six-membered ring in which the bridging
hydrogen can be replaced by metals.
x..H ‘IY
X,Y = NR, P R
0, S etc.
Such cyclic 6 x-electron systems may be classified as being
either cyclically conjugated (3) or not cyclically conjugated
(4). The characteristic difference between the aromatic (3)
and the “quasiaromatic”[lI system (4) is in the shift of the
NMR signals of the ring protons which is caused by the
ring current.
[l] Nomenclature according to D. M . G. Llopd and D. R .
Marshall, Chem. and Ind. 1964, 1760.
182
R2
R
*1
0
(4)
R
I
A
X.+Y
1
2 = H, metal
(5)
The possibility of aromatic (3) or “quasiaromatic” character ( 4 ) has been investigated in a series of H-bridged and
metal chelates of structure (5) (X = Y = NR or 0; R1,
Rz = H, alkyl, aryl, or aralkyl). In all cases, UV and NMR
results, when compared with those for model substances
in which the existence of cyclic or non-cyclic n-electron
conjugation is established, favor structure ( 4 ) , i.e. x-electron
interaction does not occur across the bridging atom Z.
This is the case for (a): the H-bridged chelates (2 = H;
X = Y = NR, where R = benzyl, phenyl, CzHs, or cyclohexyl; R1, RZ = H, alkyl, or aryl)[zJ], (b): the cyclic acetylacetonates [Z = H, Be, Zn, Al, Ga, In, Sc, Y , CO(III),Zr(rv),
Th(Iv), SnCIZ, SnBrz, SnI2, or Rh] for which aromatic
character has often been suggested, and (c): for compounds
(5) with X,Y = NR and Z = Li, Na, K, Cs, MgRz, BR, ZnR2,
[ 2 ] L. C. Dorman recently (Tetrahedron Letters 1966, 459)
assigned aromatic character to N-(3-benzylimino-l-methyl-lbuteny1)benzylarnine (X = Y = N-CHZ-C~H~,R1 = CH3,
RZ = H). The conclusionsdrawn from the UV and N M R spectra
of this compound and its salts are erroneous.
[ 3 ] Bases of type ( I ) exist as cis-trans equilibrium mixtures
( 1 ) f (2) and the position of the equilibrium is strongly dependent upon both the nature of the substituents and the solvent.
The same is true also for the metal derivatives. This should be
borne in mind when discussing the aromatic character of these
compounds.
Angew. Chent. internat. Edit.
Vol. 6 (1967)
1 No. 2
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