Structure of the Protonated Ester

Protonation of the tetrahedral intermediate at the hydroxyl-O leads to the water adduct of the protonated ester. Water is the leaving group of an E1 water elimination across a C-O bond. The loss of water yields protonated methyl formate. The elimination of water requires about 16.8 kcal/mol.

Figure. The MP2(full)/6-31G* optimized structure of the protonated ester.