Reaction Mechanism of Poly(vinyl chloride) Degradation. Molecular Orbital Calculations

摘要

The formation of conjugated polyene sequences with hydrogen chloride evolution by thermal degradation of poly(vinyl chloride) (PVC) is a chain reaction with a special mechanism called "zipper elimination." After slow HCl elimination generates isolated double bonds, fast allylic activated dehydrochlorination forms conjugated polyenes. The process is stopped at double bond sequences from 1 to approximately 30 double bonds. Although there is a wide consensus about this overall reaction sequence, the mechanism of individual reaction steps is still controversial. Free radical, ionic and molecular concerted mechanisms were proposed based on different experimental evidence.