| Popis: |
Ab initio molecular orbital and density functional theory calculations have been applied to determine the relative stability of the cyclopropylamine 1 and allylamine (CH 2 =CHCH 2 NH 2 +· 2 ) radical cations and their isomers. It is confirmed that, upon ionization, 1 undergoes barrier-free ring-opening giving the distonic species · CH 2 CH 2 CH=NH 2 + 3 . 2 also rearranges by a 1,2-H-shift to the more stable 3 (by 70 kJ/mol) which is, however, less stable than the 1-aminopropene ion (CH 3 –CH=CH–NH 2 +· 4 ) by 60 kJ/mol. The transition structure TS 2/3 lies 40 kJ/mol higher in energy than TS 3/4 . Although QCISD and B3LYP calculations of isotropic hyperfine coupling constants agree reasonably with observed values, supporting the presence of the distonic 3 in ESR matrix experiments, the exclusive observation of 3 , but not 4 , is intriguing. This emphasizes the role of the matrix in stabilizing 3 . |
Full Text from ScienceDirect