The methylamine radical cation [CH3NH2] and its stable isomer the methylenammonium radical cation [CH2NH3]

Willem J. Bouma*, Judith M. Dawes, Leo Radom

*Corresponding author for this work

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The potential energy surface for the [CH5N] system has been investigated using ab initio molecular orbital calculations with large, polarization basis sets and incorporating valence‐electron correlation. Two [CH5N] isomers can be distinguished: the well known methylamine radical cation, [CH3NH2], and the less familiar methylenammonium radical cation, [CH2NH3]. The latter is calculated to lie 8 kJ mol−1 lower in energy. A substantial barrier (176 kJ mol−1) is predicted for rearrangement of [CH2NH3] to [CH3NH2]. In addition, a large barrier (202 kJ mol−1) is found for loss of a hydrogen radical from [CH2NH3] via direct N—H bond cleavage to give the aminomethyl cation [CH2NH2]+. These results are consistent with the existence of the methylenammonium ion [CH2NH3] as a stable observable species. The barrier to loss of a hydrogen radical from [CH3NH2] is calculated to be 140 kJ mol−1.

Original languageEnglish
Pages (from-to)12-15
Number of pages4
JournalOrganic Mass Spectrometry
Issue number1
Publication statusPublished - 1983
Externally publishedYes


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