Nucleophilic Reactions of F3C- at sp2 and sp3 Carbon in the Gas Phase. Characterization of Carbonyl Addition Adducts

Article abstract of DOI:10.1021/ja00363a010

The reactions of F3C^- with CH3Br and CH3Cl established the medium kinetic nucleophilicity of F3C^- on Bohme's reactivity scale for gas-phase S_N2 reactions.The reactions of F3C^- with (CH3)2C=O and CH3CO2CH3 proceeded by competitive bimolecular H⁺ transfer and termolecular carbonyl addition giving the corresponding adducts anions m/z 127 and 143, respectivaly.F3C^- reacted with esters C6H5CO2CH3, CF3CO2CH3, and (CH3O)2C=O both by S_N2 displacement forming the corresponding carboxylate anions and by carbonyl addition yielding the adduct anions; with CF3CO2C2H5 and CF3CO2C(CH3)3, the competitive bimolecular reaction channel involved E2 elimination giving CF3CO2^-.The major reaction channel of F3C^- with HCO2CH3 was the Riveros reaction that produced the series of cluster ions F3C^-(HOCH3), F3C^-(HOCH3)2, CH3O^-(HOCH3), and CH3O^-(HOCH3)2, along with a minor amount of carbonyl addition.The fast termolecular reaction of F3C^- with (CF3)2C=O exclusively formed the adduct (CF3)3CO^- (m/z 235) which was characterized as the bound, tetrahedral structure by bracketing its proton affinity.The reaction of F3C^- with CO2 giving CF3CO2^- was established as a termolecular process when the "apparent" bimolecular rate constant was shown to be P_He dependent.These results demonstrate unequivocally that the reactions of gas-phase nucleophiles with the carbonyl group of ketones and esters proceed by addition yielding the corresponding adduct oxyanions which is analogous to the related process in the condensed phase.