ROH Molecule Assisted Elimination of F- from (CF3)2CH- and (CF3)2CD- in Gas-Phase Elcb-Type Reactions

Article abstract of DOI:10.1021/ja00258a016

The gas-phase reactions of the carbanion (CF3)2CH^- with the following series of ROH molecules, (CF3)2CHOH, CF3CH2OH, (CH3)3COH, CH3OH, and H2O, are described.In each case, formation of ROH assisted Elcb elimination cluster ion F^-(HOR)_χ (χ =/> 1) was the major or exclusive reaction channel.The reactions of (CF3)2CD^- with these ROH molecules were also examined to observe if D/H exchange occurred in the carbanion-HOR collisions and if deuterium was incorporated into the cluster ion of ROH assisted Elcb elimination.The results from the reactions of (CF3)2CH^- and (CF3)2CD^-6 with (CH3)3COH (i) the primary product ion was F^-(HOC(CH3)3)2; (ii) extensive D/H exchange was observed in (CF3)2CD^-, but no deuterium was observed in the fluoride cluster ion product; and (iii) D/H exchange and elimination occurred with the same rate constants> led to the proposal that coordination of (CH3)3COH occurred at two separate sites in the carbanion, C2 for D/H exchange and fluorine of a CF3 group for the ROH assisted Elcb elimination.The results from the collision limited reactions of (CF3)2CHOH and CF3CH2OH are consistent with this mechanistic proposal.The reactions of the carbanions with CH3OH and H2O were too slow to allow for detailed analysis.