Anchimeric assistance in the gas phase dehydrohalogenation of 5‐chloro‐2‐methylpent‐2‐ene

5‐Chloro‐2‐methylpent‐2‐ene decomposes at temperatures of 370–420°C with initial pressures from 61to 158 torr to yield hydrogen chloride and a mixture of methylpentadiene isomers. In a static system, with seasoned vessel and propene inhibitor, the reaction is homogeneous, unimolecular, and of the first order. The rate coefficient is expressed by the following Arrhenius equation: log k (sec −1 ) = (13.43 ± 0.30) − (215.0 ± 3.7) kJ/mol/2.303 RT . The result ofthe present work additionally supports the participation of the neighboringaliphatic olefinic double bond in the rate of HCl elimination of alkenyl chlorides in the gas phase. Moreover, it also confirms the three‐membered conformation as the most favored structure for anchimeric assistance.