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Macromolecular Colloquium.

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unsaturated intermediate (5) reacts with the diphosphine in
a second, rapid step, giving an intermediate (4) which forms
the chelate with loss of CO.
Received: May 12th, 1966
[Z 230 IE]
German version: Angew. Chem. 78, 646 (1966)
~~
.
A solution of ally1 isocyanate (20 g) and AIBN (1
bromotrichloromethane (200 g) is refluxed for 3 hr
steam bath. Evaporation of the excess of BrCCI3 gives
product ( l ) , which is distilled at 92-94OCi0.5 mm.
80 %, colorless oil, n2,a = 1.5269.
g) irr
on a
crude
Yield
--
[ I ] I<inetic Studies of Substitution Reactions of Metal Complcxcs, Part 4. - Part 3 : H . Werner and R. Prinz, Chem. Ber., in
press.
CHz-=CH--CH?-NCO + BrCCIS
->
[2] J . Chat? and H . R . Watson, J . chem. SOC.(London) 1961,
4980; F. Zingules and F. Canziuni, Gazz. chim. ital. 92, 343
( I 962).
[ 3 ] H . Werner and R. Prim, Angew. Chem. 77, 1041 (1965);
Angew. Chem. internat. Edit. 4 , 994 (1965); H . Werner, J. organomet. Chemistry 5 , 100 (1966).
Free-Radical Initiated Addition of
Bromotrichloromethane to Ally1 Isocyanate
By Dr. W. J. Farrissey, Jr., F. P. Recchia, and
Dr. A. A. R. Sayigh
The Upjohn Company. Carwin Research Laboratories,
North Haven, Connecticut (U.S.A.)
The addition of radical species to ally1 isocyanate has
previously not been examined. We have now found that
bromotrichloromethane undergoes rapid addition to the
C = C double bond in the presence of azobisisobutyronitrile
(AIBN) to form 2-bromo-4,4,4-trichlorobutyl isocyanate ( I ) .
CI3C-CH2-CHBr-CH:
NCO
i 1)
The N M R spectrum[ll of (1) comprises two doublets at
3.38 and 3.83 ppm (2 CH2 groups) and a 5-peak multiplet
at 4.45 ppm (CH group).
With methanol, ( I ) gives the urethane, m.p. 64-65.5"C;
with p-toluenesulfonamide in refluxing toluene it gives the
urea derivative, m.p. 185-186 'C.
With stoichiometric quantities (or less) of BrCC13 in the
synthesis of ( 1 ) the yield decreases and the amount of less
volatile material increases. Presumably telomerization occurs,
since the isocyanate function remains intact.
With CC14 in the presence of AIBN or benzoyl peroxide,
ally1 isocyanate reacts primarily at the isocyanate group.
Received: April 26th, I966
[Z 229 IEI
German version: Angew. Chem. 75, 616 (1966)
[ I ] Varian A-60 spectrometer; chloroform solution with tetramethylsilane as internal standard.
CONFERENCE REPORTS
Macromolecular Colloquium
This colloquium was held on March 3rd-5th, 1966, at the
Institut fur Makromolekulare Chemie der Universitlt Freiburg (Germany).
Studies of the Thermal Dehydrochlorination of
Poly(viny1 chloride)
D . Brriiin and M . Thallmaier, Darmstadt (Germany)
I n spite of numerous studies of the thermal removal of
hydrogen chloride from poly(viny1 chloride) (PVC), the
positions in the macromolecule responsible for initiation of
this reaction have hitherto remained obscure. To test the
effect of irregularities in structure of the PVC chains on
thermal decomposition, we have investigated the dehydrohalogenation of copolymers of vinyl chloride with small
amounts of diethyl fumarate (DEF), isobutene (IBu), vinyl
bromide (VBr), and 2-chloropropene (2-CP). The rate of
thermal dehydrohalogenation of the copolymers with VBr
and 2-CP between about 100 and 140 "Cis proportional to the
square of the mole fraction of these units in the copolymers;
it can thence be shown that the rate is proportional to the
mole fraction of those VBr or 2-CP units which are present
in sequences of two or more units. It follows that under the
experimental conditions used the liberation of a molecule of
hydrogen halide from an isolated, thermally labile structural
unit does not initiate further loss by a "zip" mechanism.
Longer polyene sequences arise only if loss of a second
molecule of hydrogen halide is possible owing to the neighboring presence of a second labile unit, or o n use of higher
temperatures. The significance of these results for the
mechanism of thermal removal of HCl from poly(viny1
chloride) and for the mode of action of heat stabilizers was
discussed.
Aiigew. Chem. internat. Edit.
/
Vol. 5 (1966) 1 No. 6
The polyene sequences arising on thermal decomposition can
be analysed by means of their electronic spectra. The regularities in polyene spectra permit approximate establishment of the distribution of polyene sequence lengths in PVC
and poly(viny1 bromide) (PVBr), and in vinyl chloride-DEF
and -1Bu copolymers. In degraded PVC, the frequency of
occurrence of sequences decreases continously with increasing
number of conjugated double bonds; in degraded PVBr,
oolvene seauences with a mean of 12 to 13 double bonds are
-~
commonest. For PVC, the ratio of the total number of
polyene sequences to the amount of HCI liberated decreases
with increasing time of degradation, i.e. with increasing
removal of HCI; the frequency distribution is shifted in
favor of shorter sequences, a result attributed to preferential
disappearance of the longer polyene sequences by secondary
reactions.
Solution Properties of Polyvinylpyrrolidone
W . Burchard, Freiburg (Germany)
Light-scattering measurements on polyvinylpyrrolidone(PVP)
in several solvents and in mixtures of solvent and precipitant show that the radius of gyration is clearly dependent
on the composition of the @-solvent (change of conformation). The change of one conformation into another is,
however, initiated far above the O-point by a relatively
small amount of precipitant. The conformational change is
particularly marked for aqueous solutions to which acetone
or dioxane has been added. Acetone causes expansion of the
coil, dioxane a contraction; ihese effects are not due to
intermolecular interactions. The conformational change is
cxplained as being due to preferential solvation of certain
groups in the macromolecule.
607
Measurements with alcohols containing alkyl groups of
various lengths also disclose a change of the unperturbed
radii of gyration with growinglength of the alkyl chain.Direct
proof of this is, however, difficult because the unperturbed
radius of gyration can no longer be taken as equal to the
radius of gyration at the @-point.
Determination of the Units in Homo- a n d
Co-polymers of Trioxane b y Pyrolysis
Gas C h r o m a t o g r a p h y
K . Burg, Frankfurt/Main-Hochst (Germany)
If homo- or co-polymers of trioxane are pyrolysed on a
platinum spiral and the products are immediately separated
by gas chromatography, the majority of the fragments
obtained at a pyrolysis temperature of 1000°C are very
hard to identify. Pyrolysis gas chromatograms of various
copolymers of trioxane show characteristic differences, so
that the method can be used for differentiation of polymers.
It is, however, not possible to draw conclusions about the
structure of the polymers from the nature of the fragments.
If small amounts of acidic reagents are mixed with the
polymers and pyrolysis is then carried out at 500°C with
subsequent gas-chromatographic analysis, considerably
simpler chromatograms are obtained. Only a few fragments
result which can be readily identified and correlated with the
structure of the polymers. The most important pyrolysis
products from polytrioxane are formaldehyde, trioxane, and
tetroxane, whereas the copolymer of trioxane and ethylene
oxide yields mainly formaldehyde, 1,3-dioxolane, trioxane,
1,3,5-trioxepane, diethylene glycol formal, and tetroxane.
Thus acetal linkages are catalytically cleaved o n pyrolysis
in the presence of an acidic reagent, the ether linkages
remaining intact. By quantitative evaluation of the chromatograms the ethylene oxide content can be determined for
copolymers of trioxane with ethylene oxide, as well as the
ratios of mono-, di-, and tri-oxyethylene units in the polymers.
Determination o f Molecular Heterogeneity of Polymers
b y Gel-Permeation C h r o m a t o g r a p h y
M. J. R . Cantow, R . S. Porter, and J . F. Johitson, Richmond,
California (U.S.A.)
Gel-permeation chromatography (GPC) permits rapid determination of the distribution of molecular size in polymers.
It consists of column-chromatography in which the stationary phase is a heteroporous swollen network whose
permeability varies over several orders of magnitudc. A
liquid phase containing dissolved polymer is passed through
the gel, whereby the polymer molecules diffuse into all parts
of the network not closed to them by virtue of their size. As a
result, the smaller molecules of the solute penetrate further
than the larger ones and are retained longer on the column.
A commerical G P C instrument (Waters), with a styrenedivinylbenzene copolymer as stationary phase, was used for
the investigation of polyisobutenes with wide and narrow
ranges of molecular weight. The average molecular weights
of the preparations lay between 2000 and 106. A computer
program is described for rapid evaluation of the experimental
results. The information fed in was the elution volume (as
measure of molecular size) and data from the registcring
refractometer (as measure of the amount of polymer). These
data are integrated numerically and the elution volumes
::re converted into molecular weights by means of a calibration curve. Two methods are described for setting up
calibration curves. The computer output consists of cumulative and differential distributions of molecular weight and
values for M,, M,, M,, M,, and M,,.1. By using these mean
values, the conventional heterogeneities, as defined by G . V.
Schulz, are calculated and tabulated. Standard deviations of
608
the differential frequency and mass distribution are also
obtained. The advantages of these values for the characterization of molecular-weight distributions by only one
parameter are discussed. By using the standard deviation,
a good correlation was obtained between non-Newtonian
viscosity and the width of the molecular-weight distribution.
Elasto-Osmometry
J . vniz Dnm, Delft (Holland)
In elasto-osmometry changes in tension in a stretched and
swollen strip of cross-linked silicone rubber are measured
at constant length. The changes in tension result from deswelling of the strip when pure solvent is replaced by polymer
solution. Swelling equilibrium is established in 10-1 5
minutes. The resulting change in tension is a function of the
chemical potential of the solvent and thus of the numberaverage molecular weight and the concentration of dissolved
polymer:
(:f1
6 C c=o
=
BRT/M,,
B is a constant dependent on the rubber used and on the
solvent.
The method gives good results for polystyrene and poly(viny1
acetate) in toluene and for cellulose triacetate in dioxane,
provided the molecular weight is above 5000. The upper
limit is a molecular weight of about 150000 with lo”/:,
accuracy.
Kinetics and Molecular-Weight Distributions in Anionic
Polymerizations in Weakly Solvating Solvents
R. V. Figitii, Mainz (Germany)
Previous studies of the kinetics and the corresponding molecular-weight distributions in anionic polymerizations were
carried out with naphthalenesodiiim as initiator and in relatively strongly solvating solvents [i-31. In order to analyse the
molecular-weight distributions more accurately, we have
selected cumylsodium as initiator, because this compound
gives only a monoactively growing chain on addition of the
monomcr; cumyl methyl ether was used as solvent, so that
the influence of its dissociative properties on the reactivity of
the ionic group could be studied simultaneously. The difference between the dielectric constant (3.7) of this ether and
those of tetrahydrofuran and tetrahydropyran (7.4 and 5.5,
respectively, at 25°C) would be expected to result in less
solvation.
The kinetic analysis showed addition of monomer in a
reaction of first order, as in systems studied earlier, and, as
expected, a smaller propagation constant of cn. 1 I.mole--1
sec-1 at -20.5”C, which is only slightly dependent on the
concentration of initiator. The dependence disappears entirely
on addition of an electrolyte (sodium tetraphenyloborate).
The mean molecular wcight increases during polyme-ization
in proportion to the monomer conversion. The molecularweight distributions of polyrners prepared without electrolyte
diverge strongly from a Poisson function; on addition of
electrolyte, the spread of the distribution decreases to such
an extent that thc dcviation from a Poisson function becomes
very small.
The results are interpreted by means of a reaction mechanism
involving two routes[I-31, in which free anions or ion pairs
[ I J If. Hostnlkn, R . V . Figin;, acid G. Y . Schulz, Makromolekulare
Chem. 7 1 , 198 (1964); R. V. Figiili, H . Hostalkn, K . Hurm,
G. Liihr, and G. V. Schulz, Z. physik. Chem. N.F. 45, 269 (1965);
H, Hostnllia and G . V . Sc!ii,/z, ibid. 45, 256 (1965).
121 IY. K . R. Bnr/iikol and G. V. Srt’ru/:, Makromolckularc Chcm.
68, 211 (1963); Sh, 298 (196s); 2. physik. Chem. N.F. 47, 89
(1965).
[3] D . N. Blrattacknryyn, C. L . Lee, J . Sinid, and M . Szworc,
Polymer 5 , 54 (1964); J. physic. Chem. 6 9 , 612 (1965).
Angew. Chem. internat. Edit.
1
Vol. 5 (1966) 1 No. 6
are considered to be propagators for the addition of monomer.
On this hypothesis, molecular-weight distributions have been
derived theoretically by the moment method [41; they agree
with the experimental results within the limits of error.
providing independent evidence for the reaction schcmc
proposcd.
Characterization of Baker-Williams Fractions by
Turbidimetric Titration
G. Gliick/rer, Dresden (Germany)
Analytical fractionation with a Baker-Williams column of
0.1-0.3 g of polymer gives many fractions containing only a
few milligrams of material. The molecular weights of such
small samples can be determined by turbidimetric titration.
Plots of turbidity vs. volume fraction of precipitant are
curves rising steeply from the abscissa. The corresponding
curves of the samples used for calibration, which were
obtained by fractional precipitation or “triangle” fractionation, rise only gradually and are S-shaped. It is therefore concluded that the Baker-Williams fractions are narrower than
those used for calibration.
The effect of the rate of elution from the Baker-Williams
column on the homogeneity of the fractions was studied. At
a rate about four times that normally used, no broadening
of the fractions could be detected turbidimetrically. S-shaped
titration curves are obtained only at substantially higher
rates of elution. This means that in the system studied
[poly(butyl methacrylate) in acetone/methanol], and presumably in other systems as well, more rapid elution than
previously thought permissible is possible.
I . Pyromellitic dianhydride and trimellitic anhydride with
p-aminophenol, ethanolamine, and p-aminobenzoic acid or
its esters afford monomeric imides containing two reactivc
groups. These iniides yield macromolecules by polycondensation with, or polyaddition to, suitable other reactants.
Thus, for instance, reaction of N,N’-bis(2-hydroxyethyl)pyromellitdiimide, the most soluble of these compounds,
with adipic acid, phosgene, or hexamethylene diisocyanate
leads to polyester-imides or polyurethane-imides, some of
which are soluble and fusible.
2. Polyimide derivatives which also are soluble and fusible
and which are stable up to more than 300°C are obtained
by polycondensation of pyromellitic dianhydride with c),f,)’bis(?-aminopropyl)polysilox~iiics( I ) :
However, use of the ester diamine (2) as diaminecomponent
yields only insoluble and infusible products.
H ~ P J -C,H, - c - 0( C H ~6-) 0C - C,H,- N H ~ (2)
It
6
0
Studies of Phase Equilibria as Basis for Fractionation
of Polymers
J . Klein, Munchen (Germany)
Investigation of Poly(viny1 dithioacetals) and their Use
as Radiation-Protecting Substances
K . Gollmrr and H. Riugsdorf, Marburg (Germany)
Vinyl dithioacetals (S-vinyl mercaptals, CH2 =CH-S-CHz-S-R)
have been prepared by dehydration of the corresponding
2-hydroxyethyl compounds and have been used for a kinetic
study of their polymerization and for the synthesis of
macromolecular compounds that might afford protection
against ionizing radiation (6OCo-y).
The over-all velocity (Vp, mole 1-1 sec--l) of polymerization
of the S-vinyl derivatives, initiated by radicals from azodiisobutyronitrile, is strongly dependent on the nature of the
substituent R :
R -iso-CjH,
iC3
V p - 0.074
C ~ H SCH3
0.553 1.056
CH=CH2 C6H5
5.67
0.767
Styrene
1.006
The assumption that there are overlapping inductive and
steric effects is supported by the results of viscosity measurcnients and by the N M R spectra of the monomers.
Investigation of the protection of mice against irradiation ‘51
has shown that copolymers of the vinyl dithioacetals with
vinylpyrrolidone are as effective as thiols of low molecular
weight but remain active for longer periods. It is, moreover,
characteristic of the polymers that they preferentially prevent
damage to the intestinal tract and consequent disturbance
of tl:e electrolyte and water balance.
Preparation and Polymerization of Difunctional
Imide Derivatives
G . Greber and R . Pense, Freiburg (Germany)
The preparation of soluble and fusible macromolecules
containing imide groups was attempted in two ways:
[4] R . V . Figitti, Makromolekulare Chem. 71, 193 (1964); R . V .
Figini, unpublished results.
[S] These investigations were carried out in collaboration with
W. Ruther at the Institut fur Strahlenbiologie und Isotopenfor-
schung der Universitat Marburg.
Angew. Cltem. internat. Edit. / Vol. 5 (1966)
/ No. 6
Fractionation of polymers is to be understood as a separation
process, dependent o n molecular weight, from a homogeneous system, with formation of a second phase. Analysis
of the phases that are in equilibrium with each other the dilute phase (sol phase) and the concentrated phase
(gel phase) - with respect to polymer content, solvent,
and precipitant shows that the phase equilibrium is univariant, as required by statistical thermodynamics.
Knowledge of the phase-equilibrium curve for the region of
the dilute solution (sol phase) is important for a description
of the fractionation, because this shows the maximum amount
of soluble polymer that can be obtained under the respective
conditions and, when the initial quantities in solution are
known, permits the fraction of polymer precipitated in one
fractionation step to be calculated.
The dependence of the equilibrium curve o n concentration
and molecular weight of the polymer, and on temperature,
were determined for the system polystyrene/benzene/methanol, with the following results:
1. Concentration: The relation between content y * of precipitant at the precipitation point (for constant M and T) and
the logarithm of the polymer concentration c* gives a
curve with a continuous curvature for measurements over a
fairly large range of concentrations.
2. Molecular weight: The content y* (for constant c and T)
is a linear function of l/Ma, where c( < 0.5, and varies with
concentration.
3. Temperature: y * is a linear function of the temperature T;
the slope of the lines is independent of c and M.
Polydispersity must be considered as a fourth parameter. By
using mixtures of samples of various molecular weights it
was shown that species of low molecular weight (which
change the number-average molecular weight) did not lead to
higher solubility ; the precipitation point is characteristic for
the partial concentration of polymer which is responsible for
the precipitation. Thence it can be concluded that the behavior of a polydisperse mixture can be described as the sum of
the behaviors of the individual components in their respective
partial concentrations. Thus the course of a fractionation
can be predicted, and the most effective system chosen, from
609
a knowledge of the analytically determined equilibrium
curves.
The above argument assumes that equilibrium is in fact
established in the fractionation process under consideration.
Effects of coprecipitation (precipitation fractionation) or
adsorption and transport phenomena (column fractionation)
can have further influences and may distort the molecularweight distribution predicted.
and 81121, Nylon 11 (H[Undl,OH, n = 2 to 5 and lo), and
Nylon 6 , 6 (H[B-A],OH, n = 2 to 5 and 10).
Synthetic procedure :
Step 1 : The initial members of the above oligoamide series
I) are converted into the readily soluble t-butoxy(n
carbonyl derivatives and these are attached by ester bonds
to chloromethylated polystyrene resin, e.g. :
~2
Studies of Mucopolysaccharides of Normal and
Sclerotic H u m a n Aortas
Alrnuth Klerner and D . Mempel, Miinster (Germany)
Normal and sclerotic human aortas, grouped according to
degree of sclerosis and age, were degraded with papain. The
contents of chondroitinsulfuric acid and heparitin sulfate were
determined by preparative chromatography. Figure 1 shows
the distribution pattern.
I t is remarkable that aortas of patients with slight sclerosis
show the highest content of chondroitinsulfuric acid.
Step 2: The amino group of the amino acid bound to the
resin is unblocked and condensed with the corresponding
BOC-amino acid by the DCC methodr31 or by the mixed
anhydride method ["I, so that the chain is lengthened by one
monomer unit.
Repetition of step 2 leads to further chain lengthening. At
the end of the synthesis the ester bond between the resin and
the oligomer is cleaved with HBr/glacial acetic acid. The
oligomer set free is precipitated as oligoamide hydrobromide.
T
Chemical Homogeneity of Binary Copolymers
G . Markert, Darmstadt (Germany)
N
gA
mA
sA
Fig. 1 . Content of chondroitinsulfuric acid ( C S ) a n d heparitin sulfate
(HMS) i n human aortas.
Ordinate: % by weight of mucopolysaccharide.
Abscissae: Degree of sclerosis.
N = normal aortas (mean age of patients: 35 years).
g A = slight arteriosclerosis (52 years).
mA = medium arteriosclerosis (63 years).
srvere arteriosclerosis (66 years)
sA
~
Relation between Synthesis of Antibodies and
Metabolism of Nucleic Acids
H. Kroger, Freiburg (Germany)
After a second immunization, spleen cells were removed from
rabbits that had been immunized with alcohol dehydrogenase.
These cells continued to form antibodies to the enzyme in
vitro. Puromycin and actinomycin D suppress this synthesis.
Therefrom it can be concluded that the antibody protein is
formed de novo, with the aid of an R N A that must originate
at the DNA. In order to investigate how the information
necessary for antibody synthesis is built u p during the first
immunization, the metabolism of D N A in rat spleen during
this period was studied. This metabolism was considerably
increased, but synthesis of R N A was only slightly greater
than in the controls.
Endoxan and 6-mercaptopurine disturb the synthesis of
antibodies. Both inhibit the synthesis of nucleic acids.
Attempts to discover a relation between the first immunization and the induction of enzymes led to the conclusion that
these processes have different mechanisms.
The changes in chemical composition of mixtures of methyl
methacrylate (MMA) and ethyl acrylate (EA) as a function
of the conversion were calculated by an iteration method
applied to the copolymerization equation. Extensive data
obtained from eight initial mixtures permit integral and
differential distribution curves to be drawn and regularities
to be derived relating to the heterogeneity of the copolymers.
The distribution curves show that the chemical composition
during polymerization changes the more the greater the
difference between the chemical composition of the starting
mixture and the polymer formed initially.
Some details can be deduced from the differential distribution
curves, namely:
Starting mixtures with 15-70 % by weight of MMA give
very heterogeneous polymers.
Of pairs mixed in reciprocal proportions the MMA-richer
polymerizes more homogeneously.
Distribution curves have the highest symmetry when heterogeneity is large.
Units for characterization of the chemical heterogeneity
proposed in the literature agree only partly with these
results. In contrast, the frequency of the various over-all
compositions provides a good measure of chemical homogeneity.
Molecular Properties and Mode of Action of
RNA Polymerase
R . L. Millette, E . Fuchs, and W. Zillig, Miinchen (Germany)
DNA-dependent RN A polymerase from E. coli has been
prepared by a method that largely precludes changes in the
~~
Synthesis of Ny l o n Oligomers by the Merrifield M e t h o d
of Peptide Synthesis on Synthetic Resins
P . Kusch, Aachen (Germany) [*I
Stimulated by the work of Merrifield[", we have prepared
oligoamides of the type of Nylon 6 (H[Cap],OH, n = 2 to 4
[*]
With collaboration by G. Kalawrytinos.
610
[I] R. B. Merrifield, Federat. Proc. 21, 412 (1962).
[2] Abbreviations:
[Cap] = -NH(CH&CO-,
[Und] =
-NH(CHz)loCO-; [B] = --NH(CHz)tjNH-, [A]' =
-OC(CH2)4CO-, BOC = (CH3)3C-O-CO-.
[3] J. C. Sheehan, G. P . Hem, and M . Goodman, J. Amer. chem.
SOC.77, 1067 (1955); 78, 1367 (1956).
[4] Th. Wieland and H . Bernhard, Liebigs Ann. Chem. 572, 190
(1951); R . A . Boissonnas, Helv. chim. Acta 34, 874 (1951).
Angew. Chem. internat. Edit.
1 Vol. 5 (1966) /
No. 6
enzyme during isolation. I t is based essentially on the high
sedimentation coefficient of the enzyme. Together with
differential centrifugation, chromatography on DEAE
cellulose, precipitation with ammonium sulfate, and separation by zone electrophoresis in a sucrose gradient lead to a
pure product that appears homogeneous in the analytical ultracentrifuge as well as on chromatography and electrophoresis. The physical and enzymatic properties of the
purified enzyme are in accord with the properties established
for the crude extract
+, 0,
~ is 24 S. The molecular
The Svedberg constant, S ~ O , W
weight is about 600000.
Electron micrographs (negative contrast) show the enzyme particles in two orientations. From these photographs a preliminary model can be derived in which six
cylindrical subunits form the wall of a hollow cylinder whose
internal “bore” has about the same cross-sectional area as a
single subunit. The length of the enzyme particle is about
95 A, the external diameter of the hollow cylinder is about
125 A, and of the “bore” about 40 A. Use of these dimensions
and this model, and assuming a partial specific volume of
0.74, permit calculation of the molecular weight as about
600000 (cf. above).
When the ionic strength is increased, the enzyme particle
dissociates reversibly into subunits of Svedberg constant
S20.w = 12 S and a molecular weight which is about one
third of the molecular weight of the 24 S particle. These
subunits no longer bind D N A and are thus enzymatically
inactive. The enzymatic activity of the enzyme concerned
with RNA synthesis is increased by raising the ionic strength.
Enzyme particles that synthesize R N A are thus neither
disintegrated nor separated from the DNA. Highly purified
enzyme, when disintegrated in 6 M urea solution at p H 3.5,
gives several bands on electrophoresis on starch gel, whence
a complex composition involving various polypeptide chains
appears probable.
The complex of DNA and polymerase can be recognized in
the electron microscope. Analysis of such photographs
provides information about the function of the enzyme.
In a cell-free DNA-dependent system from E. coii, synthesis
of proteins commences already with nascent RNA. Synthesis
of R N A and formation of protein thus proceed in the same
direction.
Activity C h a n g e s of Ziegler-Natta Catalysts by
Prepolymerization of Small Amounts of a-Olefins
H. Schnecko, P. Frevberg, M . Reinmoller, and W. Kerii,
Mainz (Germany)
Ageing of Ziegler-Natta catalysts, i.e. the action of the
catalyst components on one another at the temperature of
the subsequent polymerization, is usually carried out in
absence of the monomer. This paper reports experiments i n
which ageing of the catalyst [mainly the system AI(CzH&CI/’
Tic131 was effected in the presence of small amounts of
monomeric a-olefins (ethylene, propene, 1-hutene, or 1s
hexene). Partial polymerization of the olefins (prepolymerization) occurs during this time (usually 1 hour at 60°C).
The rate of suhsequefit actual polymerization (main polymerization) of ethylene or propene with catalysts aged i n
this way is markedly different from the initial rate. It is
lowered by preaddition of ethylene, but raised by preaddition
of propene or higher a-olefins. The differences disappear
with longcr polymerization times. It is probable that copolymers are formed between the olefins used for prepolymerization and main polymerization.
The positive and negative changes in activity of the catalyst
can in part be explained by the processes that occur in
normal ageing. However, in addition, changes in solubility
must be assumed to occur, caused by the products of the
prepolymerization.
The F o r m a t i o n of Oligomeric Amyloses b y the
E n z y m e Amylomaltase
G. V. Schulz, I f . Haselbarth, H. E. Ketler, and H. Schwinn
Mainz (Germany)
The amylomaltase discovered by Monod in 1948 has been
isolated in highly purified form. The enzyme has a sedimentation constant of 5.6 S and, o n the basis of its elution volume
from a Sephadex column, has a molecular weight of about
130000, in agreement with Wiesmeyer and Cohn’s results
(M = 124000). The turnover number is about 10500 moles of
maltose per mole of enzyme per minute, i.e. almost one order
of magnitude higher than given by Wiesmeyer and Cohn.
Amylomaltase catalyses establishment of the equilibria
Phase Separation in Solutions of Polydisperse Polymers
G. Rehuge, Aachen (Germany)
Isobaric phase-separation curves for binary systems are usually obtained from measurements of turbidity. The turbidity
curve alone does not suffice for a description of phase
separation in solutions of a polydisperse polymer. This was
shown by diffusion measurements on the system polystyrene/
cyclohexane, which shows a miscibility gap below 25 “C.
The phase-equilibrium curve varies with the initial concentration. The turbidity curve lies partly above and partly
below the phase-equilibrium curve. Its maximum is shifted
towards smaller polymer concentration and higher temperature with respect to the critical point. The position
of the critical point can be determined directly from the
course of the turbidity curve and the ratio of the phase
volumes, and indirectly from the dependence of the chemical
potential and the diffusion coefficient o n concentration. The
results are explained by means of a three-component system
consisting of the solvent and two polymeric components
of different molecular weights.
The effects observed are the stronger the higher the polydispersity of the macromolecular component. The difference
between the point of maximum turbidity and the critical
point is a sensitive criterion of polydispersity. This was demonstrated for polystyrenes prepared by anionic polymerization.
Angew. Chem. internat. Edit. / Vol. 5 (1966) / No. 6
(GI = glucose, G Z= maltose, etc.). The molar ratios of the
oligomers were determined by thin-layer chromatography
after the equilibria had been established, and the equilibrium
constants were calculated therefrom. Since separations can
be achieved up to maltopentaose, the constants K1, K2, and
K3 could be obtained and the mean equilibrium constant fT
could be calculated for the higher oligomers from their total
amounts. At 23 “C the values K1 = 0.91, K2 = 1.00, K3 =
1.03, and R = 1.04 were found.
Further experiments showed that the enzyme is not specific
for maltose but also catalyses establishment of the above
equilibriawith pure maltotriose or maltotetraose as substrate.
Thus the general reaction is
G n f Gm
+
G n + ~ -Gm-1.
t
Acid-Catalysed Degradation of Poly-3,Cacrolein
R. C. Schulz, G. Wegner, and W. Kern, Mainz (Germany)
Structurally homogeneous poly-3,4-acrolein ( I ) can be
prepared by anionic polymerization of acrolein with sodium
cyanide below 0 “C. Under these conditions, acrolein poly-
611
merizes exclusively at the C=O double bond. The polymers
are colorless powders, dissolve in many organic solvents,
and soften at 70 to 80°C. In contrast to other polymeric
then H, alkyl, or acyl, and X- is the weakly nucleophilic
anion of a strong acid. Friedel-Crafts catalysts are also
effective, and so are sulfuric acid and dialkyl sulfates, sulfonic acids and their alkyl esters, alkyl iodides, benzoyl p toluenesulfonyl anhydride, iodine, crystalline salts of 2-oxazolines with p-toluenesulfonic or perchloric acid, BF3
etherate, and p-nitrobenzenediazonium fluoroborate.
A mechanism for polymerization of 2-oxazolines is proposed
in which the active end groups consist of oxazolinium cations
that, formally from their oxonium limiting structures,
alkylate the basic monomers and thus lead to the formation
of new oxazolinium cations. According to this proposal,
“living polymers” should be formed with stable end groups
and narrow distributions of molecular weight.
Undiluted monomers are usually used for the polymerization,
but solvents may also be added.
aldehydes, which often decompose spontaneously even at
room temperature, poly-3,4-acrolein is remarkably stable,
though it also is degraded by acids. This acid-catalysed
degradation was followed viscometrically. The kinetic study
showed that degradation proceeds almost exclusively by
chain cleavage, which does not cause a “zip” reaction. The
activation energy of chain cleavage amounts to 10.6 kcal’
mole in dioxane and 12.8 kcal/mole in chloroform. Acidcatalysed depolymerization occurs only to a minor extent;
it was followed by ultraviolet-spectroscopic determination of
the monomeric acrolein formed on hydrolysis. The activation
energy of depolymerization i s 19.8 kcal/mole.
The stability of poly-3,4-acrolein towards acids is explained
by formation of a resonance-stabilized cationic fragment,
whereby the activation energy of depolymerization is greatly
increased.
Copolymerization in Systems with a PolymerizationDepolymerization Equilibrium
P . Wittmer, Ludwigshafen (Germany)
One of the conditions for validity of the well-known copolymerization equation [ I ] is irreversibility of all the growth
reactions. If this condition is not fulfilled, the depolyrnerization reaction must be taken into account. The following copolymerization equation has been derived for the case where
the propagation step in homopolymerization of one of the
two monomers (MI) is reversible:
Study of Structural Changes in Biopolymers by
Chemical Relaxation
G . Sciiwarz, Gottingen (Germany)
Structural changes of biopolymers in solution generally
comprise a very large number of individual steps. Use of
chemical relaxation for study of the kinetics of such processes
leads to relaxation curves with a complicated spectrum of
relaxation times from which a mean relaxation time can be
determined. A kinetic model of the structural change consisting of rapid growth steps and slow nucleation steps permits
the mean value to be calculated theoretically. For certain
conditions complete relaxation curves can also be calculated
on this model. A mean relaxation time of the order of 10-7
second is obtained for the helix-coil transformation of
polypeptides, and this is in agreement with current experimental results.
Polymerization of 2-Oxazolines
W . Seeliger and W. Tizier, Marl (Germany)
2-Oxazolines ( I ) can be converted into high-molecular polyN-acylethyleneimines (2) by cationic catalysts.
Polymerization of oxazolines is exothermal, the conversion of
the imino ester into the aniide structure being considered
to provide the driving force.
A temperature of at least 110°C is required for sufficiently
rapid polymerization of the 2-oxazolines. Complete conversion is generally achieved within a few hours. Interruption
of polymerization after incomplete conversion gives products
with relatively low values of the reduced viscosity.
Here K is the equilibrium constant between polymerization
and depolymerization, and X I is the fraction of the active
chains of the monomer MI with the sequence length 1. The
following equation holds for xi :
The equations contain three parameters, of which only two
are freely disposable, namely, the two r values; the third (K)
is determined by equilibrium measurements, carried out
independently of the copolymerization system.
cc-Methylstyrene was used as monomer whose polymerization
reaches an equilibrium. The constants K for various polymerization temperatures (0-100 “C) were taken from the
literature [*I. Methyl methacrylate and acrylonitrile were the
comonomers; polymerizations were radical-induced in the
absence of solvent. The new equations were found suitable
to describe the copolymerization. The temperature-dependence of the r values can be represented by Arrhenius
straight lines, as required by theory.
Preparation of Star-Shaped Polymers by Anionic
Polymerization
J.-G. Zilliox, D. Decker, and P . Rempp, Strasbourg (France)
The absence of spontaneous termination reactions in anionic
polymerizations can be utilized for various syntheses. Starshaped polystyrene molecules can be prepared by allowing
‘‘living’’ polystyrene to react with a polyfunctional deactivator, e.g. carbon tetrachloride, tribromomesitylene, or
tetra(chloromethy1)siloxane [31. The deactivation is, however,
~
~ .-.
[ I ] L. Kuchler: Polymerisationskinetik. Springer, Berlin-Gottin-
Compounds of formula ( 3 ) are suitable catalysts; they may
be added as such or produced in situ by adding strong acids
or their esters or anhydrides to the basic 2-oxazolines. R‘ is
612
gen-Heidelberg 1951, p. 162.
[2] H . W . McCormick, J. Polymer. Sci. 25, 488 (1957).
[A] See, e.g., S . P . Siao Yert, Makromolekulare Chem. 81, 152
(1965).
Angew. Chem. internat. Edit.
/ Vol. 5 (1966) / No. 6
not always quantitative, a n d steric hindrance can also occur.
I n the best cases t h e number of polystyrene chains linked t o
each other is equal to the functionality of the deactivator.
does not exceed 30‘;; of the tota amount of material.
Solvated polystyrene branches are responsible for the
solubility of the cross-linked stem which itself is insoluble.
A different method of preparing star-shaped molecules has
been developed in the authors’ laboratory: Divinylbenzene is
treated with monofunctional “living” polystyrene and
block-copolymerized. It is known that polymerization of
divinylbenzene leads t o a cross-linked insoluble polymer.
However, in the present case the polymer remains completely
soluble, provided that the amount of bifunctional monomer
T h e degree of branching depends o n the experimental
conditions and can reach high valucs. The polymeric products
can be separated by fractional precipitation; successive
fractions consist of star-shaped polymers with regularly
decreasing degrees of branching.
[VB 977 294 IE,]
Acetylation of Benzylisoquinolines
This produced mainiy 3-[2’-~-(N-ethoxycarbonyl-N-mcthylamino)ethyl - 4’3’- dimethoxyphenyi] - 6,7- dimethoxy- I - m e thylisoch:-oman (8),together with 2-[2-(N-ethoxycarbonyl-Nmethylaniino)ethyl]-2’-( 1 - hydroxyethylj - 4,4’,5,5’- tetramethoxy-tucrns-siilbeiie (7). This stilbene is a by-product and not
a n intern,eciiate in the formation of the isochroman ( 8 ) . The
N,N-dimethylamino base (70) corresponding t o (7) is converted by acid into 2-[2-(2-dimethylaminoethyl)-4’,5’-dimethoxyphenyl]-5,6-dimethoxy-3-methylindene (5’).
W . Wiegrehe, Brunsw ick (Germany )
According t o ArceIll, the reaction of the I-benzylisoquinoline
alkaloid papaverine ( I ) with acetic anhydyide and sulfuric
x
acid that affords the berbine derivative “coralyn” (2) can l
used t o identify papaverine. However, 6,7-methylenedioxy- 1(3,4-methylenedioxybenzyl)-3-methylisoquinoline(3) cannot
be converted into a coralyn derivative by acetylation. Several
hypotheses have been forwarded t o explain this failure of
coralyn formation from (3).
According t o the paraberine hypothesis, coralyn has a
paraberine and not a berbine structurc. This hypothesis
assumes, for example, that papaverine ( I ) rearranges t o
6,7-dimethoxy-3-(3’,4’-dimethoxybenzyl)isoquinoline ( 4 ) ,
from which a paraberine (4u) is formed after acetylation.
Compound ( 4 ) has been synthesized, but on acetylation docs
not give coralyn; this disproves the paraberine hypothesis.
G e r m a n version: Anqzw. Chem. 78, 638 (1966)
( 9 ) . li = OCH3’
O
R
Ji
Under the conditions of the acetylation, ( 3 ) gives 6,7methylenedioxy-1- (3’,4’-diacetoxybenzyl) - 3 -methylisoquinoline (5) and 6,7-methylenedioxy-1-(2’-acetyl-4’,5’-niethylenedioxybenzyl)-3-methylisoquinoline (6) ; the slructures of
both these products have been demonstrated by chemical
degradation a n d infrared and N M R spectroscopy and mass
spectrometry[*]. For comparison with the tetrahydroisoquinolylalcohol (6u) formed from (6), 1,2,3,4-tetrahydro-l-[2’-(1hydroxyethyl)-4’,5’-dimethoxybenzyl]-6,7- dimethoxy - 2 - m e .
thylisoquinoline was prepared and subjected t o degradation
with ethyl chloroformate r21.
eqN
0
\0
CO - C I l S
Regarding the question why (6) cannot be converted into a
coralyn analogue, Hulptrrrp [ I ] suggested that the ring closure
is prevented by the 3-methyl group, whereas Hevtel[ll
contended that it is hindered by the niethylenedioxy
substituents in the benzyl residue. The latter view is, however,
contradicted by the fact that 6,7-methylenedioxy-I-(3’-methylbenzy1)isoquinoline (10) and its I-( 3’,4’-methylene-dioxybenzyl)-6,7-~in-~ethoxyisocjuinoline
(11) yield coralyn analogues.
On the other hand, although 3-methylpapaverine ( I n ) can be
converted into its 2’-acetylbenzyl derivate (12), it does not
react further t o give a coralyn derivative, thus confirming
Hnlpuop’s view. The position of the acetyl group in (12) was
elucidated mainly by N M R spectraI31. The N M R spectra of
the bases and cations from ( I ) and (12) show that these
substances d o not possess the benzylidene structures (13)
that have been discussed as possible intermediates in
coralyn formation, despite their theoretical unlikelihood
Coralyn formation occurs by way of a (2’-acetylbenzyl)isoquinoline (14), in a mariner reiembiing the transformation
of berberine aldehyde $0 :he co-responding quaternary salt.
JJpCH3
b-J
OJ
__
[ I ] W . Awe, H. Halpaap, and 0. Hertel, Arzneirnittel-Forsch. 10,
936 (1960).
[ * ] We thank Drs. DolejS and HatiuS, Prague (CSR), for rneasur-
ing the mass spectra.
[2] J. Knabe and U . R . Shukla, Arch. Phar.naz. 295, S71 (1962).
Angew. Chem. internat. Edit.
1 Vol. 5
(1966)
1 No. 6
[Lecture a t Braunschweig (Germany), Jan. 24th, 19661
[VB 984 IE]
German version: Angew. Chem. 78, 647 (1966)
-~ .~
[3] L. Pohl and W . Wiegrebe, Z . Naturforxh. 20h, 1033 (1965).
613
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