Structure of Methyl Formate

Acid-catalyed water elimination from the tetrahedral intermediate results in the formation of methyl formate. The most stable conformer of the ester is s-cis about the C-O bond. Isomerization between s-cis and s-trans structures is facile. The s-cis isomer is about 6.4 kcal/mol more stable than the s-trans conformation. If this energy difference is considered, then the overall reaction energy for the esterification reaction becomes exothermic by about 3.6 kcal/mol.

Figure. The MP2(full)/6-31G* optimized structure of methyl formate with the C-O s-cis conformation.