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Colloquium on Macromolecular Chemistry.

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A mixture of 1 mole of ketone and 2 moles of ester is added
dropwise within 1-4 h to a stirred solution in alcohol or
ether of 2 moles of condensing agent. The whole is then left
standing for 1 --2days at O O C . Alkaline alcoholic solutions
vacuum sublimation of the residue left after evaporation of
the ether from the extract. Compound (2c) is isolated as
its picrate, made by boiling the (3-dicarbonyl compound with
picric acid in ethanol.
__
R2
Solvent
COOCrH5
COOH
Alcohol
Ether
Ether
Ether
Ether
Ether
Alcohol
[a I
fbl
H
CHI
CHC12
H
COOCzHs
COOH
CH2CI
CHO
Condensing
agent
Reaction
temp. [ “C
NaOCzHS
NaOC2Hs
NaOC2H5
NaOC2Hs
Na
NaOC2Hs
NaOC2Hs
-15
-15
0
0
-15
-15
0
Yield
I %I
__
75
80
40
25
50
45
40
[bl Obtained from (2ci by refluxing in acetic acid for 1 h with SnCl2.
Icl Obtained from ( 2 ; ) via the pyridinium salt, m.p. 223-224°C
(decomp.), and the nitrone, m.p. 207 “ C (decomp.).
are then acidified with alcoholic sulfuric acid, filtered, and
concentrated in vacuo. If alcohol-free sodium ethoxide or
metallic sodium in ether is used as condensing agent, the
reaction mixture is subsequently treated with water, and the
pyrone is isolated by acidification, extraction with ether, and
Ref.
118-119
238 (decomp.)
103- 104
86-87
141-142
132-133
127-128
280 (decomp.)
124-125
121-122
90
[cl
[a] Obtained from (2gJ by hydrolysis with conc HCI.
M. p. [ “C]
The chlorine atoms in (2e) are very firmly attached and can
be removed only under drastic conditions with simultaneous
ring-opening. Catalytic hydrogenation of (2e) over palladium-charcoal in ethanol affords a 90 yield of (2d).
Received: April 8th and May 3rd, 1965
[Z 976,402 IE]
German version: Angew. Chem. 77, 547 (1965)
[ I ] W. Borscheand W. Peter, Liebigs Ann. Chem. 453, 148(1927).
[2] S . Ruhemann, J. chern. SOC.(London) 93, 431 (1908).
[3] W. Parker, R. A . Raphael, and D. I. Wiikinson, J. chem. SOC.
(London) 1958, 3871.
C O N F E R E N C E REPORTS
Colloquium on Macromolecular Chemistry
A Colloquium on Macromolecular Chemistry, organized by
the Institut fur Makromolekulare Chemie der Universitat
Freiburg/Breisgau, was held in Freiburg/Breisgau (Germany)
on March I I-13th. 1965.
On the Chemistry of the Recombination of Insulin
Chains to Give Biologically Active Insulin
H . Znhn, B. Gutte
[*I, and 0.Brinkhofl,
Aachen (Germany)
Chemical Synthesis and Biosynthesis of Coding
Nucleic Acids
F. Cramer, Gottingen (Germany)
Condensation of thymidylic and adenylic acids with
picryl
chloride,
N,N-dimethylformamide
dichloride,
(CH3)2NCHC12, or dicyclohexylcarbodiimide leads to oligothymidylic acids and oligoadenylic acids containing up to
20 units per chain. Dinucleotides and trinucleotides of the
deoxy series can be condensed analogously to give oligodoublets and oligo-triplets. The method was used to make
(pCpT)n and (pGpApT),. Some of the oligonucleotides
prepared can be used for coding, i. e. in enzymatic tests they
function as templates for the synthesis of “copied” deoxyribonucleic acids or messenger ribonucleic acids.
When protective groups are used, oligoribonucleotides also
can be synthesized; the largest molecule of this type made so
far is a trinucleoside diphosphate, viz. UpUpC. The enzyme
polynucleotide phosphorylase was used to make mixed polynucleotides, for example poly-UG (79: 1) This ribonucleic
acid is cleaved by TI ribonuclease adjacent to the guanylic
acid residues exclusively, yielding UpUp. . . . UpC, a
polynucleotide with the terminal triplet UUG. When this
polynucleotide is used for ribosorre adaptation, it codes the
amino acid leucine, which proves that U U G is the code
triplet for leucine.
528
Crystallized bovine insulin was reduced in urea solution with
mercaptoethanol at pH 5. The mixture of SH-chains was
oxidized with air at pH 9 and 4-8 O C and dialysed. Gel filtration on Bio-Gel P-150 in ammonium hydrogen carbonate
buffer of pH 8.15 gave in 50 % yield a fraction with a molecular weight of about 140000. In this fraction, the proportion
of B-chains was 70 % (determined by amino acid analysis,
amperometric disulfide analysis, and lysine analysis with the
FDNB method [l]). In the position of native insulin, the
recombination product was found in only 5 % yield. In the
last peak, the content of A-chains is higher. The main reason
for the low yield on recombination of reduced A- and Bchains appears to be the formation of polydisulfides from Band A-chains.
Du, Jiang, and Tsou [2] achieved yields of 50 ”/, on the renaturation of insulin. Presumably polymerization is prevented here by the high pH of 10.6, since according to Fredericq [ 3 ] insulin does not aggregate at this pH.
Using another route up to 44 2 14 %, yields of insulin were
obtained, as determined o n the basis of the oxydation of
[*] B. G u f t e , Diploma Thesis, Technische Hochschule Aachen
1964.
[ I ] FDNB = fluorodinitrobenzene.
[2] Y.-C. Du, R.-Q. Jiang, and C.-L. Tsou, Scientia Sinica (Peking)
14, 229 (1965).
[3] E. Fredericq, Nature (London) 171, 570 (1953).
Angew. Chem. internat. Edit.
VoI. 4 (1965) J No. 6
glucose in rat adipose tissue: The reduced A-chain alone was
oxidized with air a t pH 8.8 for the time necessary in order to
give a n optimum yield of biologicaliy active insulin on subsequent combination with the reduced B-chain. In one experiment, the regenerated activity was optimum after 60 min
of preoxydation, in another after 100 minutes.
On gel-filtration on Sephadex G-25, these products of renaturation give a definite peak in the position expected for
native insulin. They can also be extracted with acid/secbutanol according to the method of Du et al. [4].The yield
of insulin crystals was about 20-25 % of the total activity.
Oligomerization of Peptides by Enzymatic Catalysis
H. Defernzonn, Frankfurt/Main (Germany)
In the reverse reaction of peptide proteolysis, only condensation products of relatively low molecular weight are obtained
when well-defined oligopeptides are used in the “plastein reaction”
oligop-ptide
pepsin
, polypeptide.
Thirty such peptide “monomers” - mostly pentapeptides with acidic, basic, or neutral character, of very good to good
solubilities, and with various amino acids in the chain and at
the ends, gave rise to mixtures of homologous oligomers, provided they could be condensed at all. Earlier, however, the
formation of protein-like macromolecules from protein
hydrolysates of complex composition had been reported.
Hydrolysates of this type were now separated according to
molecular weight on Sephadex G-25; subsequent treatment
of the low molecular-weight fractions with pepsin also produced only low molecular-weight plasteins. It is probable
that the products of high molecular weight described in the
older literature - where they are already contested - are to be
explained by inclusion of larger aggregates in the peptide mixture used, or by association. - The specificity of pepsin for
hydrolysis and condensations is the same with regard to the
carboxyl groups involved. Attempts were made to explain the
premature standstill that occurs in the condensation reaction
on the basis of thermodynamic considerations and a n assumption of the mechanism of pepsin catalysis.
Specific Polysaccharides of Enterobacteria
0. Westplral, 0. Liideritz, Barhnra Jnntz, and K. Jonn,
Freiburg/Breisgau (Germany)
Comparative analyses of the cell-wall lipopolysaccharides of
the S-forms of over one-hundred strains of Salmonella and as
many Esclzerichia coii strains indicated that these bacteria can
synthesize a large number of monosaccharides, including
hitherto unknown deoxyhexoses and aminohexoses, and build
them into their highly branched polysaccharides. All these
polysaccharides are constructed according to the same principle: there is a main chain of poly(heptose phosphate)
to which long side-chains are attached, which in turn may be
branched. They are the carriers of the immunological species
specificity (serotypes). The structures of the side chains were
determined by chemical, immunochemical, and biochemical
procedures; valuable information was derived from studies
of mutants (R-forms) with enzyme blocks (of synthetases
and transferases) in the polysaccharide biosynthesis. Serological and chemical analysis of the R-forms revealed
that all the polysaccharides from Salmonella S-forms (wild
strains) have a common basic skeleton (bas21 polysaccharide)
in which short oligosaccharide chains containing glucose,
galactose, and glucosainine are linked to poiy(heptose phos[4] Y.-C. Du, Y.-S. Zhang, Z:X.
Sinica (Peking) 10, 84 (1961).
Atigew. Chem. internot.
phate). I n S-forms, the recurrent units of the long 0-specific
side chains are attached to the terminal glucosamine residue
of the basal polysaccharide.
Chemical and genetic classification of Snlmotiella and other
enterobacterial genera will be possible o n the basis of the
structure of the recurrent oligosaccharide units and their
structural variation. On treatment with phages, various structures can be transformed into others (lysogenic conversion).
In this way, the serological classification (Kauffmann-White
scheme) is supplemented by a biochemical-genetic system of
classification.
Many strains of E . coli form not only cell-wall (1ipo)polysaccharide (0-antigen) but also a capsule antigen (K-antigen),
which forms a layer on the cell wall over the 0-antigen. Many,
but not all K-antigens have been found to be long-chain polysaccharides containing uronic acids. The structural principle
of some K-antigens and the structures of their determinant
group(s) were determined. - In addition to 0- and K-antigens, mucoid coli bacteria produce another mucoid substance
(M-antigen; called colanic acid by W. F. Coebel), which is
also a n acidic polysaccharide. With the aid of the phenol/
water procedure, all the polysaccharides can be extracted
from the bacteria and can then be separated with Cetavlon
[ 5 ] into purified K- and M-antigens (acidic polysaccharides)
and 0-antigen (lipopolysaccharide). Highly diverse sugar
monomers can be involved in the construction of the K-, M-,
and 0-specific polysaccharides from one and the same bacterium.
An Enzymatic Method for Kinetic Investigations
of Endohydrolases: Assay of the Activity of u-Amylase
R . Werner and C . Keilich, Freiburg/Breisgau (Germany)
The kinetics of the degradation of polysaccharides by endohydrolases - which split the macromolecule within the
chain - normally can be studied accurately only if the alterations in molecular weight are followed. Determination of the
number-average molecular weight is possible with the aid of
an exohydrolase, which splits off single monomers from the
chain ends, because the rate of reaction of the exohydrolase
depends o n the number of end groups available. Since the
action of the endohydrolase gives rise to new end groups, the
rate of the exohydrolase reaction increases; its acceleration
is therefore a measure for the activity of the endohydrolase.
This new method for assaying endohydrolases was illustrated
with a-amylase. The exohydrolase used was a polysaccharide
phosphorylase. Its rate of reaction can be measured by
determining spectrophotometrically the glucose- 1-phosphate
formed using phosphoglucomutase and glucose-6-phosphate
dehydrogenase. The activity of the a-amylase is expressed directly in international units, namely pnoles of glucosidic
bonds hydrolysed per minute. The method can in principle be
applied to any endohydrolase, provided specific exohydrolases are known for its substrate.
The Molecular Weights of Native Dextrans
K. Ehert, Miinchen (Germany)
On the basis of determinations carried out in the ultracentrifuge or by light scattering, extremely high values, viz. about
5 x 108, had been obtained for the molecular weights of
native dextrans. According to molecular kinetic estimations,
based on the molecular activity of the synthesizing enzymes,
such large molecules should be formed only after prolonged
reaction times.
A method was developed for measuring the number-average
molecular weights (Mn) of native dextrans: the terminal saccharose grouping is split off with a n enzyme and the resulting
aldehydic end group is reduced with tritium-labelled lithium
Lu, and C.-L. Tsou, Scientia
Edit. VoI. 4 (1965) / No. 6
[ S ] Cetyltrimethylarnmonium bromide.
529
borohydride; the specific radioactivity can then be correlated
to M,. In this way, M, values of around 2 x l o 5 were obtained for dextrans formed at low substrate concentrations.
These values are in agreement with the results of fractionation
in a Baker-Williams column. The higher values previously
found are ascribed to aggregates.
Kinetic Studies on the Biosynthesis of Cellulose
the fibril already present there, and are bonded by hydrogen
bridges. The layers of parallel fibrils result because a system of
synthesis tubes slides along the cell wall, carried along by the
flow of the cell plasma.
Fractionation of High Molecular-Weight Materials on
Silica Gels Having a Defined Cavity Structure
H. W . Kuhlschiitter, Darrnstadt (Germany)
M. Marx-Figini, Mainz (Germany)
The amounts of cellulose and its degree of polymerization in
hairs from cottonseed a t different stages of ripening were
determined and correlated with the age of the seeds.
The results showed that the biosynthesis of cellulose proceeds
in two phases. In the first phase, the synthesis is slow, and
only little cellulose is formed. The majority is produced during the second stage, which starts spontaneously; here the
synthesis proceeds much faster. The assignment of the first
and second phase to the formation of the primary and
secondary cell wall, respectively, was confirmed by the values
found for the degrees of polymerization (D. P.) and by the
swelling properties of the seed hairs, the longitudinal growth,
and the amount of non-cellulosic materials formed at the
various stages of maturity.
The DP increases by almost one order of magnitude o n passing from the first to the second reaction phase and then remains constant throughout the entire synthesis of the secondary cell wall. It is independent of the conversion and the rate
of reaction and is practically completely uniform. It must
therefore be concluded that during the biosynthesis of cellulose in higher plants, templates ensure the maintenance of a
constant DP.
In connection with systematic investigations of the structural
material, the cavity systems, the surface, and the natural grain
formation of silica gel, high molecular-weight polystyrenes
dissolved in chloroform were fractionated and polystyrene/
paraffin mixtures were separated on silica gel columns. The
separations are occasioned by partition of the dissolved
materials between the mobile phase of the solvent flowing
around the silica gel grains and the quasi-stationary phase of
the solvent entrained within the large pores in the grains. The
partition of the dissolved materials and the separatory efficiency of the column can be related by a simple equation. The
chromatograms were evaluated with the aid of molecularweight determinations. The component with the highest
molecular weight correponds to the smallest, that with the
Lowest molecular-weight to the greatest retention volume.
The efficiency of the columns increased when silica gel preparations with larger specific pore volumes were used.
The same silica gel preparations were used to separate inorganic salts and colloids in aqueous solutions. Analogous relationships were found between the particle weights and the
retention volumes, and between the specific pore volume of
the silica gel and the separatory efficiency of the columns.
Polychelated Siloxanes
Model Concepts of Cellulose Synthesis and of the
Formation of Plant Cell Walls
G. V. Schulz, Mainz (Germany)
The studies of M . Marx-Figini (see report above) make it
appear probable that the biosynthesis of cellulose is controlled by templates. Attempts were made to develop concepts as to the nature of the synthesizing system on the basis
of the properties of cellulose and of morphological observations. It follows from the molecular weight that the template
must be about 5 x 14000 A = 7 p long.
Electron micrographs of cell walls (Frey-Wyssling, Miihlethaler, Preston) reveal that the secondary cell wall consists of
fibrils of uncertain lengths and with diameters between 50 and
150 A. These are arranged parallel in layers which cross at
definite angles. This structure excludes the possibility that
cellulose molecules synthesized o n the template are released
directly into the cell plasma. If this were so, the long glucosidic chains would fold up into single molecule crystals
(Bittiger and Husemann), which could afterwards hardly combine to form fibrils and become properly oriented in the
highly organized tissue of the secondary cell wall. Moreover,
a simple calculation, and degradation experiments carried out
with cellulose (Rrjnby), have made it appear likely that the
crystallographic micelle described by Hengstenberg and
) is in reality a folded single
Mark’[ca. 50 x 100 x ( ~ 6 0 0A31
molecule and that the fibrils are linear sequences of folded
molecules.
By consideration of the electron-microscopical observations
of Miihlethaler and Ledbetter, a mechanism is proposed for
cellulose synthesis which incorporates three partial processes:
( I ) synthesis, (2) fibril formation (spinning process), and (3)
deposition of fibrils in criss-cross layers (weaving process).
The template occurs (stretched or spirally coiled) in a pipeor tube-like structure. The interlinking ofthe glucose units begins at one end in such a way that a continuously folding
chain molecule is formed which on completion reaches the
other end of the tube in the form of a “folded package”. There
the loops of the folds become inserted into those of the end of
530
A . Hofer [TI, H. Kuckertz, and M . Sander,
FrankfurtlMain (Germany)
Polymethylsiloxanes of types ( 1 ) and (2) containing metal
chelate groups were synthesized in various ways. Type (I)
compounds contained mainly M = Be or A1 with p-diketones
(acetylacetone) as chelating agents. The siloxanes containing
beryllium attain a viscosity number of 0.4 dl/g, are solid at
room temperature, and have a broad plasticity range between 60 and 20OoC. They decompose above 170°C, the
main pyrolysis gas being methane.
Type (2) compounds could be obtained only with titanium
chelates (8-hydroxyquinoline). These polymers are generally brittle up to 100 OC. Above 200 ‘ C , rearrangements of
Si-0-Ti bonds to Si-0-Si and Ti-0-Ti bonds occur.
The Preparation and Polyaddition Reactions of
Ferrocene Derivatives with Two Dimethylsilyl Groups
G. Greber and M . L . Hallensleben, Freiburg/Breisgau
(Germany)
Reduction of 1 ,1’-bisdimethylethoxysilylferroceneand 1,l’bis(dimethy1-n-butoxysily1methyl)ferrocenewith LiAIH4 leads
to good yields of 1 ,I,-bisdimethylsilylferrocene( I a) and 1 , I , bis(dimethylsily1methyl)ferrocene ( 1 b ) , respectively.
In the presence of H2PtC16 as catalyst, these add onto acetylene to form 1,I’-bis(dimethylvinylsilyl)ferrocene ( 2 a ) and
1,l’-bis(dimethylvinylsilylmethyl)ferrocene(2 b ) , respectively.
[t] Since deceased.
Angew. Chem. infernat.Edit. / Vol. 4 (1965)
1 No. 6
Polyaddition of ( I n ) and ( 2 u ) or of ( I b) and ( 2 b) as well as of
( I ( I ) or ( I b) and other organosilicon compounds containing
two alkenylsilyl end groups or of (20) or (2b) and other organosilicon compounds containing two terminal H-Si groups
reactions were studied using the model reaction between
caprolactam and N-methylacetamide hydrochloride, which
gives rise to acetylcaprolactam and oligo(aminocaproy1)-Nmethylacetamides.
(2b), n =
affords thermostable polymers containing ferrocene residues as
links in the main chain. Depending on the ratio of the reagents used, the end groups in the final product may be either
two hydrosilyl or two alkenylsilyl moieties.
On heating for 6 h at 300”C, polyadducts made from ( l u )
and (20) decrease in weight by only 0.1
whereas those
from ( l b ) and (2b) by about 5 %,.
x,
Polymeric Reaction Products Made from Formaldehyde
and Nitriles Containing Activated Methylene Groups
W. Frrtrke, Stuttgart (Germany)
Oligomers Obtained in Cationic and Anionic Polymerization of e-Caprolactarn
M . Rotlie, Mainz (Germany)
The mechanism of the cationic and anionic polymerization
of e-caprolactam and the structures of the resultant polymers
were studied using oligomers of uniform molecular size [6].
Reaction of e-caprolactam for short times with equimolar
amounts of initiator (in cationic polymerization: HCI, sulfonic acids, ortho-, pyro-, or polyphosphoric acid, or
BF3,HzO; in anionic polymerization: Na lactamate plus Nacyl-e-caprolactam) yielded mixtures of oligomers which
were separated by chromatography and electrophoresis; the
products were studied by spectroscopy and identified by
comparison with authentic synthetic samples of caprolactam
oligomers.
On cationic polymerization, oligo-(e-aminocaproy1)caprolactams up to the hexamer were detected and isolated o n a micropreparative scale. Their structures were confirmed either by
their synthesis from N-protected oligoaminocaproyl chlorides and caprolactam with subsequent removal of the
protecting group (carbobenzoxy or azido residues) or by their
reaction with hydroxylamine, which cleaves o f fthe terminal
lactam rings to give the corresponding oligoaminocaproylhydroxamic acids. The chain initiation and chain growth
[6] In collaboration with H. Boenisch, D. Essig, K . Gehrke,
G. Reinisch. and I. Rothe.
Vol. 4 (196.5)
Radical Polymerization of Itaconic Acid
D. Brortn and I . A . Aziz El Sayed, Darmstadt (Germany)
During free-radical polymerization of itaconic acid
When phenylacetonitrile is condensed with formaldehyde in
methanol in the presence of sodium methoxide as catalyst,
liquid or crystalline polymeric products of relatively low
molecular weights are obtained, depending on the molar
proportions of the reactants and on the reaction conditions.
Insoluble polymers are obtained similarly from phenylenediace t on i t r i le .
Experiments with low molecular-weight model substances
based on phenylacetonitrile revealed that under the conditions used, the condensation reaction leads first to a-cyanostyrene and that it depends largely o n the ratios of coreactants and o n the temperature whether this product undergoes
a Michael addition with unchanged phenylacetonitrile to form
2,4-diphenylglutarodinitrile or whether a n anionic polymerization occurs in which low molecular-weight poly-a-cyanostyrene is formed as a result of premature chain termination.
The polymers obtained contain methoxy and some hydroxymethyl end groups. In addition, some terminal nitrile groups
are converted into imino ether groupings.
Angew. Cliern. iiitermrt. Edit.
In anionic polymerizations, the first three members of the
series of N-acetyloligo(aminocaproyl)caprolactams were
detected. In order t o test for branching, bis-(e-aminocaproy1)-e-aminocaproic acid was synthesized.
Cationic and anionic lactam polymerization lead via different
mechanisms to polymers with the same litctam end-groups.
/
No. 6
the carboxyl group content in the polymerizing system
decreases in proportion to the amount of polymer formed. At
the same time. carbon dioxide is liberated to an extent
independent of the nature of the initiator and of the solvent.
The polymers have only about one-half of the carboxyl
group content to be expected for poly(itaconic acid). - In
free-radical copolymerizations of itaconic acid, carbon
dioxide is also evolved.
The carbon dioxide liberated originates from the primary
carboxyl group in the monomer ( I ) ; no carbon dioxide is
released during the polymerization of the corresponding
monoester of itaconic acid.
Analytical and spectroscopic investigations of the polymers
yield some information concerning their structures. Subsequent reactions of the carboxyl radicals split off give rise to
hydroxyl and formyl radicals during the polymerization, and
some of these are incorporated into the polymer and can
later be determined therein.
The mechanism of the free-radical polymerization of itaconic
acid is not yet completely explained, but model reactions
permit conclusions to be drawn as to the nature of the course
of reaction.
Metal Chelate Complexes as Polymerization lnitiators
N . Nuarmtrnn, Ludwigshafen/Rhein (Germany)
Metal chelates (acetylacetonates) can be used to initiate
vinyl polymerizations.
The efficiency of the complexes as initiators depends on the
central atom and on the complexing ligand, as illustrated by
the polymerization of styrene. Manganese(II1) and cobalt(II1)
chelates of aliphatic P-dicarbonyl compounds are the most
effective.
The metal chelate initiators can be activated by high-energy
radiation or by combination with cocatalysts such as organic
halogen compounds ( e . g . n-amyl chloride) or polyunsaturated
hydrocarbons ( e . g . cyclooctadiene).
Several findings indicate a free-radical mechanism. The
central metal atom influences the steric structure of the
polymer chains. Thus the content of cis-l,.l-residues in polybutadiene is particularly large when the chelated metals have
ionic radii of 0.6-0.7 A. A minimum content of cis-1,4linkages occurs when the ionic radius lies around 1.0 A.
53 1
Emulsion polymerization of butadiene with metal chelate
complexes as initiators gives polymers with significantly
higher contents of cis-1,4-configurations and correspondingly
low glass transition temperatures.
G r a f t Polymerization of Vinyl C o m p o u n d s o n t o
Ethyleneflinyl Acetate Copolymers
H. Bnrtl and D . Hordt, Leverkusen (Germany)
Because of their active hydrogen atoms, ethylene/vinyl
acetate copolymers form good bases for graft polymers. They
were used as substrates for graft polymers with vinyl acetate,
acrylic and methacrylic esters, acrylonitrile, styrene,vinylidene
chloride, and vinyl chloride. The greatest amount of grafting
is achieved by using the technique of suspension polymerization; here the ethylene/vinyl acetate copolymer is dissolved
in monomer, the solution is dispersed In water containing a
protective colloid, and allowed to polymerize.
The tendency towards graft polymerization is proportional
to the activity of the monomer radicals (under comparable
conditions): vinyl chloride captures the greatest amounts of
substrate, and the acrylic esters and acrylonitrile respectively
less; styrene has only a very low capacity for grafting on
ethylene/vinyl acetate copolymers.
The physical properties of the graft copolymers depend
largely on whether the final products are mutually compatible.
Styrene graft polymers have a low compatibility, while vinyl
chloride graft polymers are compatible at all compositions
and even i n admixture with pure poly(viny1 chloride). Graft
copolymers with high vinyl chloride contents have properties
akin to hard poly(viny1 chlorides) of high impact strength,
while those with high substrate contents are similar to soft
poly(viny1 chlorides).
Polymerization o f Formaldehyde b y Adsorbed W a t e r
G. Schruder, Darmstadt (Germany)
If anhydrous gaseous formaldehyde is passed into a suspension of a n inorganic salt in a hydrocarbon, high molecular-weight polyoxymethylene dihydrates are obtained
under certain conditions. Experimental findings lead to the
conclusion that the polymerization proceeds by a n anionic
mechanism. The reaction is started at the crystal surface by
the water adsorbed there. Although the polymer deposited is
compact, the inorganic salt can be readily extracted with
water.
This process has the following technical advantages over the
polymerization of formaldehyde in the presence of tertiary
amines:
I . Because of the compactness of the polymer formed,
reactors of a given capacity can be used more economically.
2. Any traces of catalyst remaining in the polymer d o not
accelerate degradation of the polymer during subsequent
processing.
3. The demands placed on the purity of the monomer and
solvents in order to attain technically utilizable molecular
weights are less stringent.
Transfer Reactions during the Cationic Polymerization
of Trioxane
V. Jnncks, Mainz (Germany)
During the cationic polymerization of trioxane in the presence
of low molecular-weight esters, anhydrides, acetals, or
readily hydrolysable ethers, transfer reactions occur leading
to thermostable polyoxymethylenes containing ester or ether
end-groups. Analogous transfer reactions can also occur
at the C-0-C groups of high molecular-weight polyesters,
532
polyethers, or polyacetals. The products are then thermostable block or graft polymers, depending on whether the
transferring group is in the main chain of the polymer, as for
example in poly-l,3-dioxolane or poly(ethy1ene terephthalate), or in a side group as in poly(viny1 acetate). The influence exerted on the transfer reaction by water was discussed.
I t is surprising that polyoxymethylenes stable to heat and
alkalies are obtained in yields up t o 65 % of the total products
during homopolymerization of highly purified trioxane as
well ; this is ascribed to intramolecular transfer reactions.
Copolymerization of Formaldehyde with Cyclic Formals
H.-D. Hermant?,Frankfurt/Main-Hochst (Germany)
Formaldehyde was copolymerized with cyclic formals in the
presence of cationic catalysts. Pure monomeric formaldehyde
was passed into an inert hydrocarbon in which the catalyst
was dissolved, the comonomer being added simultaneously.
Series of experiments were conducted by varying the polymerization temperature between -20 and +80 "C, the catalyst
concentration between 0.01 and 0.2 % by weight (based on
the monomers), and the comonomer concentration between
2 and 2 0 % by weight. The comonomers used were 1,3dioxolane, 1,3-dioxane, 1,3-dioxacycloheptane, 1,3,6-trioxacyclooctane, and 1,3-dioxa-5-cycloheptene.The catalysts
were TiC14, B F ~ . ( C ~ H ~ ) ZSbCl5,
O,
and SnC14.
The copolymerization did not follow the equation of M o p
and Lewis. It is striking that the incorporation of comonomer
is favored by increase in temperature and catalyst concentration. The nature of the catalyst is also an important factor
influencing the composition of the copolymer. Antimony
pentachloride and tin tetrachloride proved to be particularly
effective catalysts.
Chemically uniform copolymers of high molecular weight,
stable towards alkali, were obtained only over a restricted
range of polymerization conditions, e. g. from formaldehyde
plus 10% by weight of 1,3-dioxacycloheptane with about
0.05 by weight (based on monomers) of SnC14 at 60-80 "C.
The anomalous behavior of the copolymerization reaction
is explained by transacetalizations between polymer molecules. This transacetalization [7] is promoted by increases in
temperature and catalyst concentration, and its occurrence
is proved by the fact that a uniform copolymer was obtained
o n polymerization of formaldehyde in the presence of a
prepolymer containing formal groups.
Synthesis and Autoxidation of Poly(vinylthio1)
W. H. Daly, K. Burg, and C. G. Overberger, Brooklyn
New York (U.S.A.) and Mainz (Germany)
S-Vinyl-0-t-butyl thiocarbonate was produced by simultaneous esterification and dehydrohalogenation of S-@chloroethyl) chlorothioformate with potassium t-butoxide.
On polymerization with free-radical initiators, it yielded
poly-(S-vinyl-0-t-butyl thiocarbonate), which was transformed into poly(vinylthio1) by removal of the t-butoxycarbonyl groups either by treatment with anhydrous hydrogen
bromide or by thermolysis of the thiocarbonate substituents.
The course of the latter reaction is analogous to that of the
decomposition of methyl xanthate according to Tschugaeff.
The autoxidation of poly(vinylthio1) to the disulfide was
studied in dimethyl sulfoxide using ferric sulfate as catalyst.
The rates of oxidation of low molecular-weight dithiols were
measured under standardized conditions and compared with
that of the polymer; the following sequence of reactivities
was observed: poly(vinylthiol)>2,4-pentanedithiol>2,5hexanedithiol>2,6-heptanedithiol. The reaction was of the
[7] CJ K. Weissermel, E. Fischer, K . Gutweiler, and H . D. Hermann, Kunststoffe 54, 410 (1964).
Airgew. Chem. itlternot. Edit.
1 Vol. 4 (1965) !No. 6
first order with respect to the Fe(1lI) ion and zero order
with respect t o the thiol content of the dithiols within the
concentration range examined. A redox reaction between an
Fe(II1)- and a n Fe(I1)-thiol complex is postulated as a step of
the autoxidation. The oxidation of the poly(vinylthio1) was
not independent of the thiol concentration. Shielding of
mercapto groups within the polymer coil and their reduced
mobility may be possible explanations.
Investigations on the Molecular-Weight
Jump Reaction of 1,4-cis-Polybutadiene
W. Ring and H.-J. Caritow, Maid (Germany)
The stereospecific polymerization of butadiene according to
Ziegler to give cis-polybutadienes with a catalyst system
containing a n organocobalt and a n organoaluminum compound occurs in homogeneous solution. Limits are set to the
technical polymerization by the increase in viscosity resulting
from the progress of thereaction and the increase in molecular
weight of the polymer. However, an increase in molecular
weight can be achieved after conclusion of the polymerization
by adding reagents such as alkyl or acyl halides [8].
The mechanism of this molecular-weight jump reaction and
its influence on the structure of the molecules was studied. It
was shown that a cationic reaction mechanism is involved by
using [14C]-t-b~tyl chloride as reagent for boosting the
molecular weight, by determining the molecular-weight
distribution using a Baker-Williams column, and by viscometry and light-scattering photometry.
The average molecular weight, the distribution of molecular
weights, and the molecular configuration can be controlled
by selecting suitable reactlon conditions.
Oxidation of Transition Elements by Organic Halides ;
Detection of Radicals by Polymerization Kinetics
G. Henrici-Olive and S. OlivB, Zurich (Switzerland)
Colloidal suspensions of transition elements in tetrahydrofuran undergo electron transfer reactions with organic halides
such as carbon tetrachloride or benzyl chloride. The metal is
oxidized, e . g . Coo --f C O ~ ' and
~ , the carbon-halogen bond is
split, giving rise to a free radical capable of initiating the
polymerization of vinyl compounds.
Polymerization of methyl methacrylate was started in this
way with the following metals: VO, Cro, Feo, Coo, Nio, and
Pto. The free-radical mechanism of the polymerization was
proved by the observed validity of the usual rate equations
for free-radical kinetics and by copolymerization of methacrylate and styrene.
The rate of formation of the free radicals can be estimated
from the overall rate of polymerization by following the
reaction dilatometrically, and is different from one metal to
another. For example, under comparable conditions at 9 0 "C,
it is at least 300 times slower for vanadium than for cobalt.
Consequently, the polymerizations can be carried out with
VO at this temperature to high conversions with a practically
constant free-radical concentration, whereas the concentration
of free radicals from Coo falls off with a half-life of 4-5 min.
Some New Aspects for the Quantitative Interpretation
of Flow Birefringence
H. Janeschifz-Kriegl and U.Dnum, Delft (Holland)
The flow properties of solutions of macromolecular substances are generally characterized by two phenomena :
a) the dependence of the viscosity on the velocity gradient,
and b) the occurrence of elastic stresses.
[ 8 ] E. F. Engel, Marl (Germany), 3rd International Synthetlc
Rubber Symposium, London, October 13-15th, 1964.
Angew. Cheni. internat. Edit.
V d . 4 (1965) / No. 6
Investigation of flow birefringence proves to be a powerful
tool for appraisal of the elastic properties. With this technique, the average coil expansion occurring during flow
can be determined for dilute solutions at least [9]. This
parameter can be considered as a (reduced) contribution of
the individual molecules to the (elastic) tensile stress in the
direction of flow. The experimental results obtained with
solutions of anionically prepared polystyrenes show that the
theory developed by Zimm [lo] for the dynamic behavior
of macromolecules applies up to an expansion which corresponds to an average increase in the end-to-end distance of
about 10 7; (relative to the value at rest). Surprisingly, even
for these small expansions, tensile stresses can be expected in
dilute solutions of a magnitude corresponding to viscometrically determined shearing stresses.
The situation becomes more complicated with polydisperse
substances. The coil expansion corresponding to the tensile
stress becomes an effective parameter which can be referred
to the average expansion of the molecules with the aid of a
polydispersity factor (Peteriin). The polydispersity factor
increases sharply as the molecular-weight distribution becomes wider. When the distribution of molecular weights I S
broad, it also depends critically on the form of the distribution
function. For example, the applicability of a Schulz distribution could be excluded for Marlex 5065 - a linear polyethylene - on the basis of the flow birefringence of its solution
in trnns-decalin at 135 "C.
Crystalline Compounds of Poly(ethy1ene oxides) and
Polyesters with Urea and Thiourea
A. Kohier, G . Hild, and R.M n y e r , Strasbourg (France)
Crystalline adducts of urea with poly(ethy1ene oxide), its
derivatives containing end groups, or its block copolymers,
are formed in a heterogeneous reaction on saturation of
crystalline urea with a solution of the polymer in benzene.
On the average, these adducts contain 28 % poly(ethy1ene
oxide).
These compounds have a hexagonal crystal lattice which
however does not resemble that of the channel-like inclusion
compounds of urea.
Thiourea behaves similarly, but the content of poly(ethy1ene
oxide) in its adducts is much higher.
Adducts of urea with polyesters are obtained in both heterogeneous and homogeneous medla. They have a maximum
polymer content of 33 and belong to the hexagonal crystal
system which characterizes the classical inclusion compounds
of paraffins in urea.
We can now interpret the fractionation of polyesters on urea
observed by W. Kern as being due to selective addition of the
urea to the polymer fractions with the highest molecular
weights. Poly(ethy1ene oxides) can also be fractionated by
formation of their urea adducts.
<:
Chlorinated Poly(viny1 chloride)
W. Trcrurvetter, Troisdorf (Germany)
The technical chlorination of poly(viny1 chloride) is carried
out mainly by two methods: 1 . in solution, and 2. in gels
made by swelling PVC in a non-solvent. The products have
the same chlorine contents but different properties (shape
retention, solubility, stability, etc.).
The causes for the differences in properties were investigated,
assuming that chlorinated products with approximately
-(CHCI-CHC1)-,
and
equal amounts of -(CHz-CHCI)-,
-(CHZ-CCl*)units are formed by both processes. Crosslinking during the chlorination of the gels or great non[9] A . Peterlin, J. chem. Physics 39, 224 (1963).
[lo] B. H. Zimm, J. chem. Physics 24, 269 (1956).
533
uniformity in the degree of chlorination as possible explanations may be excluded. It is probable that products are
formed during the chlorination in gels with great differences
in the lengths of the sequences of the three basic structural
units.
Elucidation o f the Microstructure of Polymers by
Nuclear Magnetic Resonance Specrroscopy
U. Johnsen, Darmstadt (Germany)
The proton resonance spectra of vinyl polymers with a
simple cc-substituent are much easier to analyse when the
coupling between the a- and @-protonsis cancelled by double
resonance. This method was used t o elucidate the microstructures of some poly(viny1 chlorides).
The spectra reveal that o n chlorination of PVC, the methylene
groups are substituted with three to four times higher
probability than the chloromethylene groups. I n addition t o
non-chlorinated monomer units, the chains contain only the
structural units -(CHCI-CHCI)and -(CCI~-CHZ)-. The
frequency of recurrence of these structural units, the average
lengths of uniform blocks made UD of these units. and the
chlorine contents of the products studied were determined.
KGa02 is the first compound of the KFeO2 structure-family
with a proven structure. According to powder photographs
this family includes the cubic or pseudocubic compounds
KFeOz (a = 7.958 8)111, RbFeO2 (a = 8.10 A) [2], CsFeO2
(a = 8.32 8)[21, KAlO2 (a = 7.79 A) 131, RbAlO2 (a =
7.73 A) [41, CsA102 (d = 8.10 A) [4], RbGa02 (rhombic,
a = 5.64 A, b = 11.37 A, c = 16.19 A, isotypic with KGa02)
141, CsGaO2 (rhombic, a = 5.83 A, b = 11.68 A, c = 16.50 A,
perhaps isotypic with KGa02, possibly also cubic with
a = 16.50 A) [41, and, according to single-crystal investigations, the cubic CsScOz (a = 17.45 A) [4]. As already supposed from powder photographs these compounds have a
“filled framework structure” of the $-cristobalite type.
Distances for K G a 0 2 : Ga-0 = 1.68-1.95 8 ( 4 x ) ; K - 0 =
2.53-3.52
A
(8x).
NaGaO2 [51 occurs as two modifications; the low-temperature form (a) is of the B-NaFe02 type according to
single-crystal investigations, and is a variant of the wurtzitetype. The rhombic unit cell with a = 5.301 A, b = 5.519 A,
c = 7.201 A, space group CZv-P2lnb, contains four formula
units; all particles occupy the equivalent positions 4 (a), with
the parameters:
l x
[VB 910/228 IE)
Na
Ga
German sersion: Angew. Chem. 77. 509 (1965)
01
0 2
0.240
0.746
(0.81)
0.418
I -B
I y
0.410
0.061
0.395
0.060
0.126
0.123
0.173
0.102
2.70
1.05
1.70
1.60
On the Chemistry of Amphoteric Oxides
R. Hoppe, Miinster (Germany)
Amphoteric metal oxides can react with “acidic” non-metal
oxides [e.g. T I 2 0 3
3 SO3 + Tl~(S04)3] as well as with
“basic” metal oxides [ e . g . TI203 + NazO -f 2 NaT1021.
Little has been reported on ternary oxides of the alkali metals
which, like NaT102, belong to the second group of compounds.
+
Many new oxides have been prepared which, according to
their crystal structure, represent transitions between the
extreme types“mixed oxide” and ‘‘0x0 complex”. Of these, the
following are noteworthy:
The previously unknown oxogallates KGa02, RbGaOz, and
CsGaO2 were prepared at 400-450 ”C in 20-24 hours under
dry nitrogen, e.g.
2 CsO1.25
+ Ga203
+ 2 CsGaOz
They are colorless powders and extremely sensitive to moisture. The crystal structure of KGaO2 was determinedon
single-crystals using Fourier methods. KGaOZ crystallizes
pseudocubic, orthorhonibic with a = 5.515 A, b = 11.076 8,
and c = 15.818 A, with Z = 16 formula units per unit cell
Idx-ray = 3.87 and dpyk = 3.78 g.cm-31 in the space group
D:;-Pbca. All particles occupy the equivalent position 8 (c)
with the following provisional parameters:
X
Y
2
-B
0.260
0.279
0.749
0.008
0.189
0.065
0.062
0.186
0.014
0.100
0.59
0.68
1.71
1.12
0.796
0.578
0.170
0.286
0.905
0.264
0.014
0.264
0.298
0.404
0.173
0.479
0.155
0.224
C. Boron, Djjon (France)
Preparative, enzymological, and physiological investigations
of two liver enzymes were discussed. These enzymes play
a role in the metabolism of healthy and cancerous cells which
has but little been studied. They are catalase, an otherwise
well-investigated enzyme, and amine oxidase, of the properties of which relatively little is known.
As catalase has a healing effect on skin injuries, experiments
with artificially (by calcium triphosphate) produced granulomas were performed. Catalase caused intensive fibroblast
proliferation and the formation of collagen fibres.
The enzyme preparations were crystalline catalase and less
pure amine oxidase preparations. This second enzyme is
firmly attached to mitochondria and thus difficult to enrich.
Detergents, especially a 0.2 %, solution of sodium lauryl
sulfate at p H 7 and 20 OC, proved most effective in loosening
this attachment. In this way, it was possibIe to bring into
solution about 30 of the enzyme, without loss of activity,
in the first step, and a further 20 % in the second step. The
preparations were free from diamine oxidase activity.
2.46
0.46
1.75
2.77
Of 976 possible reflections (Okl) to (4kl), 663 have been
observed; Mo-K, radiation; I, determined photometrically
from “integrated” Weissenberg photographs, R = 0.153 and
R‘ = 0.25.
534
Recent Investigations on Oxidases and Peroxidases
[ I ] S . Hilpert and A . Lindner, Z. physik. Chern. B 22, 395 (1933).
[2] C.-J. Brendel, G. Wehrmeyer, and W. Klemm, unpublished
work; cf. G. Wehrmeyer, Ph. D. Thesis, Universitat Miinster 1959.
[3] L . T . Brownmiller, Amer. J. Sci. 29, 260 (1935); T. F. W.
Earth, J. chem. Physics 3, 323 (1935).
[4] Author’s own investigations.
[ S ] Recently prepared by B. N . Ivanov-Emin and J . I . Rabovik,
Zhur. obshch. Khim. 17, 1061 (1947).
Angew. C h m . internut. Edit.
Vol. 4 (1965) 1 No. 6
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