Degradation and stabilization of poly(vinyl chloride). III. Correlation of activation enthalpies and entropies for dehydrochlorination of chloroalkanes, chloralkenes and poly(vinyl chloride)

• Published in: Polymer degradation and stability Vol. 45; no. 3; pp. 325 - 338
• Main Authors: Bacaloglu, Radu, Fisch, Michael
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 1994
• ISSN: 0141-3910; 1873-2321
• DOI: 10.1016/0141-3910(94)90202-X

Activation enthalpy-entropy correlations for the experimental data available for dehydrochlorination of chloroalkanes and chloroalkenes in the gas and in the liquid phase or non-polar solvents show that this reaction has two possible mechanisms: chloroalkanes, 3-chloro-1-alkenes ▪ and trans 1-alkyl-3-chloro-1-alkenes ▪ (gas phase) eliminate HCl through a transition state of four centers requiring a synperiplanar conformation of the ▪ group (Scheme 1). Cis 1-alkyl-3-chloro-1-alkenes ▪ and trans 1-alkyl-3-chloro-1-alkenes (liquid phase) and conjugated 1-alkyl-5-chloro-1,3-alkadienes ▪ eliminate HCl through a transition state of six centers requiring a cis configuration of the double bond (Scheme 2). The activation parameters for the elementary reactions of PVC degradation fit on the same correlation lines supporting, for the initiation reaction, a mechanism involving a transition state of four centers and for propagation and termination reactions, a mechanism involving a transition state of six centers.