Kinetics of Unimolecular Decomposition of Excited Alkylamine Ions

The unimolecular reaction RCH2NH2+→R+CH2NH2+ has been studied for the n-alkylamines from ethyl- to n-heptylamine inclusive by a mass spectrometric technique. The intensity of the metastable ion produced in the above reaction was measured and used to determine the variation of the specific rate constant with the internal energy of the molecular ion. The results are compared with those predicted by various theories. The agreement of the data with the theories of Kassel and of Rosenstock is bad for the smallest molecules but improves with increasing number of oscillators in the molecule. Earlier evidence for intramolecular vibrational relaxation in the parent molecular ions is discussed in relation to the assumptions of Slater's theory. A simplified application of Slater's theory seems unable to explain all the data.