Kinetics of the reactions of cyclopropane derivatives. Part I. The gas-phase unimolecular thermal isomerisation of 1,1-dichlorocyclopropane

Abstract

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.