UNIMOLECULAR REARRANGEMENTS OF CARBANIONS IN THE GAS-PHASE .2. CYCLOPROPYL ANIONS

We have examined the gas-phase unimolecular rearrangements of a series of substituted cyclopropyl anions (CHXCH2CY-; X = H, Y = Ph, CHO, and CN; X = Y = CO2CH3) with a variable temperature flowing afterglow device. The ring-opening barriers range from 19 to greater-than-or-equal-to 36 kcal mol-1 and are well reproduced by ab initio molecular orbital calculations. An analysis of eight monosubstituted cyclopropyl anions reveals that the flexibility (ease of inversion) and thermodynamic stability of these ions account for their tendency to isomerize.