Isomerisation reactions of β-ethyl anions in the gas phase

Abstract

Evidence based primarily on the technique of collisional activation mass spectrometry is presented which suggests that substituted β-ethyl anions (XCH₂CH₂^–) are at best transient species in the gas phase often rearranging to more stable isomers, e.g., MeCOCH₂CH₂^–→ MeCOCHMe, PhCOCH₂CH₂^–→ PhCOCHMe, HOCOCH₂CH₂^–→ MeCH₂CO₂^– and CH₂CHCH₂CH₂→^–CH₂–CHCH–Me. The β-methoxycarbonylethyl anion MeOCOCH₂CH₂^– is presumably unstable with respect to its radical since no peak corresponding to either this species or a stable isomer is observed.