ON THE FORMATION OF THE CH2CH2CH = NH2-CATION UPON IONIZATION OF CYCLOPROPYLAMINE AND ALLYLAMINE( DISTONIC RADICAL)

Ab initio molecular orbital and density functional theory calculations have been applied to determine the relative stability of the cyclopro pylamine 1 and allylamine (CH2 = CHCH2NH2+ 2) radical cations and thei r isomers. It is confirmed that, upon ionization, 1 undergoes barrier- free ring-opening giving the distonic species CH2CH2CH = NH2+ 3. 2 als o rearranges by a 1,2-H-shift to the more stable 3 (by 70 kJ/mol) whic h is, however, less stable than the 1-aminopropene ion (CH3-CH = CH-NH 2+ 4) by 60 kJ/mol. The transition structure TS 2/3 lies 40 kJ/mol hig her in energy than TS 3/4, Although QCISD and B3LYP calculations of is otropic hyperfine coupling constants agree reasonably with observed va lues, supporting the presence of the distonic 3 in ESR matrix experime nts, the exclusive observation of 3, but not 4, is intriguing, This em phasizes the role of the matrix in stabilizing 3. (C) 1998 Elsevier Sc ience B.V. All rights reserved.