Intramolecular methyl migration in the protonated N,N′-dimethylpropane-1,3-diamine and N,N′-dimethylethane-1,2-diamine

Intramolecular methyl migration in the protonated N,N′-dimethylpropane-1,3-diamine and N,N′-dimethylethane-1,2-diamine were studied by tandem mass spectrometry. Using density function theory at B3lyp/6-31g (d) level, intramolecular SN2 methyl migration in the protonated N,N′-dimethylpropane-1,3-diamine and N,N′-dimethylethane-1,2-diamine were found to proceed by a high-energy inversion mechanism or by a high-energy retention mechanism. With the number of bond between two nitrogen atoms in diamine increasing, the inversion mechanism becomes more favorable.