Mass spectroscopic observation of an ester formation reaction between benzoic acid and alcohol initiated by multiphoton excitation in a liquid beam

An alcohol solution of benzoic acid, C6H5COOH, was introduced into a vacuum as a continuous liquid flow (liquid beam) and irradiated with a laser beam at a wavelength of 272 nm; the alcohols used were ethanol and propanol. Ions produced by multiphoton excitation in the liquid beam and ejected from it were analyzed by time-of-flight mass spectrometry. The mass spectra of the ions produced from benzoic acid in these different alcohol solutions led us to conclude that a protonated benzoic acid, C6H5C(OH)(2)(+), produced by laser irradiation reacts with an alcohol molecule, ROH, in the solution and that C6H5C(OH)(2)(ROH)(+) and C6H5C(OH)(OR)(+) are produced. Some of the product ions are regarded as reaction intermediates of ester formation from benzoic acid and the alcohols.