Heat of formation for the methylenimmonium cation by photoionization mass spectrometry

Eur. J. Mass Spectrom. 10, 759–766 (2004)
DOI: 10.1255/ejms.681

Heat of formation for the methylenimmonium cation by photoionization mass spectrometry

Zoë A. Harvey and John C. Traeger^*
Department of Chemistry, La Trobe University, Victoria 3086, Australia. E-mail: j.traeger@latrobe.edu.au

ABSTRACT:

Photoionization mass spectrometry has been used to measure the CH₂NH₂⁺ appearance energies for six primary amines, resulting in a 298 K heat of formation of 749.5 ± 1.3 kJ mol^–1 for the methylenimmonium cation. An absolute proton affinity of 868.8 ± 2.5 kJ mol^–1 is derived for methylenimine. Based on experimental data for ethylenediamine, the 298 K heat of formation for the aminomethyl radical is found to be 153.6 ± 1.7 kJ mol^–1. These results are supported by high-level ab initio calculations.

Keywords: methylenimmonium cation (CH₂NH₂⁺), methylenimine (CH₂NH), aminomethyl (CH₂NH₂), photoionization, proton affinity, heat of formation, appearance energy

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