Methylketene. Ion Chemistry and Proton Affinity

Article abstract of DOI:10.1021/ja00535a040

The gas-phase ion chemistry of methylketene has been investigated using a quadrupole ion store (quistor) as an ion/molecule reaction chamber.The reaction sequences have been elucidated by the new technique quistor resonance ejection (QRE), which closely resembles ion cyclotron double resonance (ICDR).The ion chemistry of methylketene is analogous to that of ketene, and the nonreactive species m/z 57 (C3H5O⁺) is a major product at long storage times.The equilibrium for proton transfer between methyl acetate and methyl ketene ((CH3COOCH3)H⁺ + CH3CHCO = CH3CH2CO⁺ = CH3COOCH3) has been studied and the proton affinity (PA) of methylketene was found to be 845 +/- 3 kJ mol^-1, based on a value for PA(CH3CO2CH3) of 839 kJ mol^-1 relative to the PA(i-C4H8) at 828 kJ mol^-1.