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Oligoamides and their Role in Lactam Polymerization.

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band is observed which is so sharp that it cannot be attributed
to a relaxation effect; its nature has not yet been elucidated.
E. W. Jones and W. J. Orville-Thomas (Aberystwyth, Wales,
Great Britain) have carried out measurements of ultrasonic
absorption to determine the difference between enthalpies
(AH N 0.9 to 2.1 kcal/mole) of rotational isomers in the
liquid state. These values differ appreciably from those
obtained from infrared measurements (AH
0 to 0.83
kcal/mole). The data o n sound absorption apparently lead
to incorrect values of AH. It can be shown that, in the case
of rotation around a C-C bond, the basic assumptions used
for calculating the enthalpies are incorrect. On the other
hand, the values obtained for the activation energies are
acceptable.
-
Relaxation of Excited Molecular Vibrational States
R . C. Millikan (Schenectady, N.Y., U.S.A.) surveyed the
processes of energy transfer in the gas phase. In favorable
cases, the vibrational relaxation times can be found with a n
accuracy of & 20%. Millikan also discussed the effect of
rotation on the vibrational relaxation, the exchange of
vibrational energy on collision, and the energy transfer
between molecular vibrational states and excited electronic
states of atoms and free electrons.
H. J . Bauer and H . Roesler (Stuttgart, Germany) dealt with
the relaxation of the vibrational degrees of freedom in
binary mixtures of diatomic gases. An exchange reaction
between the excited and the non-excited molecules of different
components of mixtures ensures a coupling between the
relaxation processes of the two components. The two relaxation times for the sound absorption of the entire system
depend in a complicated manner o n the composition. The
reciprocal relaxation times give a conic curve when plotted
against the mole fraction. They were determined experimentally by measuring the sound absorption in 02/Nz
and in 02/CO mixtures. With the aid of these values, the
transition probability for the return to the ground state at
300 and 365 OK was found, e.g. for 0 2 / 0 2 collision at 300 OK,
t o be 8 . 3 10-9.
~
P B 956/263 IE]
German version: Angew. Chem. 78, 120 (1966)
Translated by Express Translation Service, London
Oligoamides and their Role in Lactam
Polymerization
M . Rothe, Mainz (Germany) [I]
Higher linear oligomers or pleionomers of E-aminocaproic
acid containing up to 14 monomer units per chain and their
derivatives with protected amino and carboxyl functions
were synthesized via the carbobenzoxyoligoamide benzyl
esters using the phosphite method conventionally [2] or occasionally on a polymeric support [3]. Cyclic oligomers containing up to 8 monomer units per ring were obtained by
cyclizing the chain compound by the phosphite method [2].
Separation of the linear oligomers with up to 7 monomer
units was achieved by thin-layer electrophoresis and the
separation of cyclic oligomers containing up to 8 monomer
residues by thin-layer chromatography with n-butanol/
acetic acid/ammonia (1 :4)/water ( 6 : 1 : 1 : 2) or with ethyl
acetate/acetone/water (10: 10: 2).
In the absence of water, oligomers with N-terminal amidinium
groups ( I ) d o not initiate cationic lactam polymerization
even on heating them with the monomer at 250 “C for several
hours. Hence the formation of terminal amidinium groups
during lactam polymerization [4] does not contribute to
normal chain propagation [ S ] , but causes chain termination. Higher lactams, e.g. caprylolactam or laurolactam do
not form amidine rings in appreciable amounts, since these
would have to have 9 or 13 ring members.
[Lecture at Marl (Germany),
June 16th, 19651
[Vd 945/252 IE]
German version: Angew. Chem. 78, 151 (1966)
[ I ] In collaboration with D . Es.yig, I. Rothe, and H . Schneider.
[2] M. Rothe et al., Makromolekulare Chem. 75, 122 (1964).
[3] R. B. Merrifield, J. Amer. chem. Soc. 85, 2149 (1963).
141 P. Schlack, Z . ges. Textilind. 1963, 1052; reported in a lecture at the Synthetic Fibre Symposium, Berlin, March 30th, 1965.
[5] M . Rothe ef at., Makromolekulare Chem. 54, 183 (1962).
The Influence of Neutral Salts on the Hydrogen
Ion Activity
K . Schwabe, Dresden (Germany)
It was shown by comparison of potentiometric, polarographic,
and spectrophotometric measurements of pH in dilute
solutions of strong acids and bases that the addition
of large amounts of neutral salts produces a genuine,
occasionally large change in the pH. The conventional
p H value was determined using glass and hydrogen
electrodes. Simultaneous measurements of the pwH and
ptH values [l] revealed that shifts sometimes as large as 2 p H
units were caused by a change in the activity coefficient of the
hydrogen ion at constant hydrogen ion concentration. In
salts with a common anion, the p H shift to lower values
increases as the radius of the cation decreases; with very large
cations, e.g. quaternary ammonium ions, an increase in p H
may be observed. With a common cation, the shift to higher
p H values becomes greater, the smaller the radius of the
anion. Salts with large, non-hydrated ions e.g. NH4CNS,
cause only small changes in pH, even at very high concentrations (> 20 moles/kg). The decrease in the p H of acids usually is proportional to the molality m of the salt. The same
applies for some cations, e . g . Lie, for the reduction in the
p H of alkali metal hydroxide solutions; in other cases, e . g .
with sodium salts, the p H of sodium hydroxide solution
passes through a minimum as the amount of salt added
increases.
The results can be interpreted by assuming that the change in
the activity coefficients of H e (or OHe) is caused by the
electrostatic interaction of the charge of the H e (or OH@)
ions, which is “smeared out” uniformly over the whole
solvent on account of the rapid exchange with water molecules, and the cations and anions of the salt. With the additional assumption that this interaction increases with the
number of water molecules held in the hydration sphere of
the salt ions, an equation can be set up for the excess Gibbs
free energy of the Heions which fits at least the experimental
values for the decreases in the p H of acids ApH/Am,,lt.
The binding of water molecules by hydration of the salt and
the resultant increase in the H e concentration in the “quasieutectic” system and the observed decrease in the product
mHWmOHQ at high salt concentrations may also contribute
to the change in pH. It was shown that the kinetics of decomposition of acetoacetic ester and of the anodic dissolution of
F e and Co depend o n the H e activity, but that cathodic discharge of He depends upon the He concentration.
[Lecture at Saarbriicken (Germany), July 16th, 19651
[VB 953/254 IE]
German version:
Angew. Chem. internnt. Edit.
/ Vol. 5
(1966)
/ No. I
Angew.
Chrm. 78, 151 (1966)
141
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lactam, role, polymerization, oligoamide
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