The possible reaction mechanisms for the gas-phase thermal deamination of isopropylamine, tert-buty-lamine, and dextroamphetamine in the presence of hydrogen bromide are investigated by DFT calculations with several functionals. In each case, QTAIM analysis supports the formation of an ion-pair complex, which subsequently decays through a six-membered cyclic transition state (TS). NBO charges and interatomic lengths suggest the polarization of the N-1(delta)center dot center dot center dot C-delta+(2) bond in the TS is rate determining. (C) 2018 Elsevier B.V. All rights reserved.