Site of Gas-phase Methylation of 1-Phenyl-2-aminopropane

Article abstract of DOI:10.1002/oms.1210260610

The regioselectivity of methyl cation transfer from (CH3)2F(1+), (CH3)2Cl(1+) and (CH3)3O(1+) to 1-phenyl-2-aminopropane was studied by Fourier transform ion cyclotron resonance in combination with collision-induced dissociation and neutralization-reionization mass spectrometry of the stable (1+) ions formed in a chemical ionization source.The (CH3)2F(1+) ion transfers a methyl cation to the NH2 group and the phenyl ring with almost equal probability.Predominant CH3(1+) transfer to the NH2 group is observed for the (CH3)2Cl(1+) ion whereas the (CH3)3O(1+) ion reacts almost exclusively at the amino group.The preference for m ethylation at NH2 is discussed in terms of a lower methyl cation affinity of the phenyl ring than of the amino group and the existence of an energy barrier for methylation of the phenyl moiety.