ISOMERIZATION-REACTIONS OF BETA-ETHYL ANIONS IN THE GAS-PHASE

Evidence based primarily on the technique of collisional activation mass spectrometry is presented which suggests that substituted beta-ethyl anions (XCH2CH2-) are at best transient species in the gas phase often rearranging to more stable isomers, e.g.. MeCOCH2CH2- --> MeCOCHMeBAR, PhCOCH2CH2- --> PhCOCHMeBAR, HOCOCH2CH2- --> MeCH2CO2- and CH2=CHCH2CH2 --> -CH2-CH=CH-Me. The beta-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.