Evidence of proton-induced cyclization of α,ω-diamines from ion mobility measurements

Abstract

The mobilities in air at 250°C of protonated normal primary aliphatic amines, cyclic amines and α,ω-diamines were measured by ion mobility spectrometry (IMS) techniques. The mobility of the protonated α,ω-diamines was higher than that of the protonated cyclic amines, which was higher than that of the protonated normal primary amines. It was found that cyclization leads to an increase in mobility, which is slightly mass dependent, and charge delocalization in the diamines leads to a further increase in the reduced mobility. These results indicate that upon protonation, internal hydrogen bonding takes place in the α,ω-diamines.