The reaction between t-BuOH and FeCl3 to form tert-butyl cation is computed to be lower in free energy by 26.7 kcal•mol - 1 suggesting it is far more likely to occur. Considering the reaction is run in the presence of a strong Brønsted acid, we also examined how protonation of the alcohol group affects these energetics. First, protonation of the alcohol group by HCl is predicted to be significantly thermodynamically uphill (ΔG° = 28.8 kcal•mol -1 ). The free energy for subsequent cleavage of the C-O bond in the presence of FeCl3 and FeCl2 are computed using eq. 3 (ΔG°/ΔH° = -5.8/-4.0 kcal•mol -1 ) and 4 (ΔG°/ΔH° = 40.1/44.1 kcal•mol -1 ):