Ion-Molecule Reaction between a Protonated Phenyl Ketone and an Alcohol Following Multiphoton Excitation in a Liquid Beam

Article abstract of DOI:10.1021/j100042a044

An alcohol solution of phenyl ketone C6H5COR1, where R1 is CH3, C2H5, H, or C6H5, was introduced into a vacuum as a continuous liquid flow (liquid beam) and irradiated with a laser beam at wavelengths of 250, 280, and 355 nm.Ions produced by multiphoton ionization in the liquid beam and ejected from it were analyzed by time-of-flight mass spectrometry.The mass spectra of the ions produced from various alcohol solutions of phenyl ketones at different excitation wavelengths indicate that a protonated phenyl ketone ion, C6H5C(OH)R1(1+), produced by laser irradiation reacts with an alcohol molecule, R2OH, in the solution and C6H5C(OR2)R1(1+) is produced.This reaction corresponds to the initial process for acetal formation from a phenyl ketone and an alcohol, and these product ions are identified to be its reaction intermediates.When an alcohol solution of benzophenone, C6H5COC6H5, was used, a pinacol ion, (C6H5)2C(OH)C(OH)(C6H5)2(1+) was produced in addition to C6H5C(OR2)C6H5(1+).The appearance of the pinacol ion suggests the presence of benzophenone dimers in the vicinity of the liquid surface.