Endocyclic versus exocyclic mechanisms for methyl migration in protonated N,N'- Dimethylpropane-1,3-diamine

Abstract

A recent paper has suggested that an endocyclic methyl transfer pathway occurs in competition with methylamine loss for protonated N,N'-dimethylpropane- 1,3-diamine under conditions of low-energy collision induced dissociation [X. Zhang, S. Yao and Y. Guo, Int. J. Mass Spectrom. 214, 277 (2008)]. However, such endocyclic methyl transfers appear to be unprecedented in the gas phase. Therefore, in order to gain additional insights into the competition between methylamine loss and methyl transfer in this system, DFT calculations were performed at the B3LYP/6-311+G(d,p) level of theory for a number of competing mechanisms. Three mechanisms were considered for loss of methylamine: (i) a 1,2-elimi..