Alcohol Dehydration: Protonated Alcohol Substrate

The dehydration of alcohols requires acid catalysis. Protonation of the alcohol O atom converts the poor leaving group hydroxide into the excellent neutral water leaving group. The proton transfer from hydronium ion to the alcohol is exothermic by about 27.1 kcal/mol.

Figure. The MP2(full)/6-31G* optimized structure of protonated 2,3-dimethyl-2-butanol.