SynopsisThe reactions of model molecules were considered to study the kinetics and the mechanism of the esterification and the alcoholysis reactions catalyzed by various metal compounds (Li, Na, K, Zn, Co, Mn, Ti). Ti was found to be the most active catalyst for both reactions and to be acting via a different mechanism (concerted). The possible structure of the active titanium intermediate was investigated by means of 'Hand 13C-NMR spectroscopy, FT-IR spectroscopy, and electroconductivity.
SynopsisWith a reaction conducted on model molecules with low amounts of catalysts and at low temperatures (170-225"C), it was shown that esterification is mainly catalyzed by the carboxylic acid groups and by the titanium derivatives; the activity of the other metals can only be seen when the concentration in carboxylic acid groups is low. In the alcoholysis reaction, the activity of Zn, Mn, and (much less) Ti, decreases when the percentage of ester in the reaction medium decreases, whereas it is the opposite with Sb. Moreover, Zn, Mn, and Co are sensitive to trace amounts of carboxylic groups (their activity decreases), whereas Ti is much less affected.
Theoretical and experimental data for the composition and structure (microheterogeneity) of copolymers obtained by nonequilibrium copolycondensation in homogeneous systems are considered. The effect of the relative reactivities of the comonomers, the reactivities of the first and second groups of the intermonomer, the order and duration of addition of the initial compounds to the reaction zone, and other factors on the composition and microheterogeneity of the copolymers has been demonstrated in relation to interbipolycondensation. The available experimental literature data have been compared with the results of calculations based on a quantitative theory of homogeneous copolycondensation. The bibliography includes 57 references.
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