Using trimethylamine as base (Figure ) resulted in an activation free energy (B3LYP+GD3+BJ/Def2-TZVPP/SCRF(DCM)) of +14.8 kcal/mol. To compare this energy with that of the subsequent reactions of 2 and 3, two models were investigated. The first is a supermolecule of the exo-TS containing a hydrogen-bond bound Me3NH + .Cl -, which emerged as 7.1 kcal/mol lower than the initial proton abstraction step k0. The second is an additive model of the exo-TS in which the free energy of Me3NH + .Cl -is added to that of the exo-TS and this emerges as 10.5 kcal/mol lower. This result supports the claim 9 that k0 is the slow step in the overall reaction and that the reactions k1-4 represent faster intramolecular reactions. We also note that the formation of 1 itself has some interesting stereochemical features. The second aspect is the process connecting the endo-and exo-transition states (kinv, Scheme1). Firstly, we note that the reversible proton transfers connecting species 1 with 2 or 3 (Scheme 1) serve as such a mechanism, noting previously that this process is higher in free energy than reactions k1-4.