The mechanism of propene elimination from the immonium ions CH2N+(CH3)CH(CH3)2 and CH2N+(CH3)CH2CH2CH3

Abstract

It is shown by ²H-labelling experiments that β-hydrogen transfer from the propyl group to the nitrogen atom is not an adequate general explanation for propene loss from CH₂N⁺(CH₃)C₃H₇ ions: β-hydrogen transfer occurs for CH₂N⁺(CH₃)CH(CH₃)₂, in which the N-alkyl substituent corresponds to a stable isopropyl cation; but α- and γ-hydrogen transfer dominate for CH₂N⁺(CH₃)CH₂CH₂CH₃, in which isomerisation of the unstable incipient n-propyl cation precedes propene expulsion.