Neighboring group participation of polar β substituents in the gas-phase pyrolysis of 2-substituted ethyl chlorides

✍ Scribed by Gabriel Chuchani; Ignacio Martin; Gonzalo Martin; David B. Bigley

• Publisher: John Wiley and Sons
• Year: 1979
• Tongue: English
• Weight: 362 KB
• Volume: 11
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550110202

✦ Synopsis

Abstract

The pyrolysis of 2‐dimethylaminoethyl chloride in the temperature range of 360–400°C and the pressure range of 60–271 mmHg is a homogeneous, unimolecular, first‐order reaction giving dimethylvinyl amine and hydrogen chloride. 2‐Methoxyethyl chloride pyrolysis in the temperature range of 450–490°C and the pressure range of 53–110 mmHg by a similar unimolecular, first‐order reaction yields methylvinyl ether and hydrogen chloride. These reactions were carried out in a seasoned reaction vessel and in the presence of a propene inhibitor. The methylvinyl ether decomposes slowly into other products at the temperature of pyrolysis. The rate constants are given by the Arrhenius equations

(a) 2‐dimethylaminoethyl chloride:

(b) 2‐methoxyethyl chloride:

The effects of polar β substituents in the 2 position of ethyl chloride are discussed in terms of anchimeric assistance and electron‐withdrawing deactivation in these elimination reactions. The present results are consistent with the heterolytic nature of the four‐centered cyclic transition state for the gas‐phase pyrolysis of alkyl halides.