Science Record

SCIENCE RECORD _ New Ser. Vol. III, No. 1, 1959

CHEMISTRY

STUDIES ON THE POLYESTERIFICATION OF DIBASIC ACIDS AND GLYCOLS Il, ON THE RELATIONSHIPS BETWEEN THE VELOCITY CONSTANTS OF POLYESTERIFICATION AND THE MOLECULAR STRUCTURES OF DIBASIC ACIDS AND GLYCOLS*

Tance Au-cHIn** (BE#U), Yuo Kuo-sur (RE), Su CHu-rr (JB) anp Liv Cutn-po (x7) (Institute of Applied Chemistry, Academia Sinica)

On the basis of our own many experimental results and a great number of foreign authors’ data we have suggested a new mechanism of hydrogen ion catalysis in esterification, polyesterification and three dimensional polyesterification reactions and clarified the long disputed question of the order of the esterification and polyesterification reaction" *.

A fundamental assumption of the kinetics of polycondensation reactions is that all similar functional groups have the same reactivity and hence the same velocity constant K is independent of the chain-length of the molecules themselves. Flory’! has attempted to confirm this assumption with studies on the kinetics of polyesterification reactions between three pairs of dibasic acids and glycols, but due to the mechanism and the order of polyesterification reaction remaining unclarified, of course, the velocity constants calculated by him according to the kinetic equation of third order reaction are meaningless. The present report is chiefly concerned with the relationships between velocity constants and molecular structures of dibasic acids and glycols. Hence, in order to prove the fundamental assumption we have studied the kinetics of polyesterification reactions between thirty five pairs of dibasic acids and glycols.

According to the theoretical analysis of our first report''!, when dibasic acids and glycols react in equivalent quantity ratio in the absence of foreign acid, the results of polyesterification reactions satisfy the following kinetic equation:

3/2 2 (+) —1=2KCH:, (1)

*Received Nov, 19, 1958.

**Member of Academia Sinica ’