The potential energy surface for gas-phase reactions of ammonium ion with alcohols was examinedby ab initio and DFT methods. Transition structures for inversion (SN2) and retention (SNF)mechanisms were located for 2-propanol and exo-2-norbornanol. The SNF (retention) process wasfound to be 6−8 kcal/mol higher in energy than the inversion SN2 counterpart for the 2-propanolsystem. The retention process in the 2-exo-norbornanol/ammonium ion system was favored by 1.3kcal/mol.