KINETICS OF REACTIONS OF CYCLOPROPANE DERIVATIVES .1. GAS-PHASE UNIMOLECULAR THERMAL ISOMERISATION OF 1,1-DICHLOROCYCLOPROPANE

The gas-phase thermal isomerisation of 1,1-dichlorocyclopropane to 2,3-dichloropropene at 342-441° and 20-120 torr is first-order and unaffected by changes in surface-to-volume ratio or by the addition of nitric oxide or propene. The first-order rate constants fit the Arrhenius equation: log10k(sec.-1) = (15.13±0.10) - (57,810±300)/4.576T. The nature of the product virtually excludes a mechanism in which ring-expansion or formation of a biradical intermediate is important, and the reaction is interpreted as a unimolecular process in which the transition state is formed basically by migration of a chlorine atom along the ring with little distortion of the carbon skeleton.