MASS SPECTROMETRIC DETERMINATION OF PROTON AFFINITIES OF VARIOUS MOLECULES

The proton affinities of a number of simple molecules have been determined by a combination of techniques. Observation of proton transfer reactions between molecules establishes a relative order of proton affinities. Absolute values are then estimated by an empirical method involving measurement of translational energies of products of an ion-molecule reaction. The proton affinities found by these two methods are consistent with each other and with values obtained from appearance potentials. The proton affinities range from 126 kcal/mol for methane to 211 kcal/mol for methylamine.