Theoretical study of acetylation of methanol

Abstract

Theoretical study of acetylation of methanol from the analysis of intermediate of the reaction was carried out. The study of acetylation of alcohols is of great interest by the utility of its products of reaction and is one of the most frequently used transformations in organic synthesis as it provides an efficient means for protecting hydroxyl groups in a synthetic process. Acetylation of alcohols is a nucleophilic substitution reaction. This reaction can be catalyzed by Brönsted acid. In the mechanism, the acetic anhydride first accepts a proton at the carbonyl oxygen and this change enhances the positive charge on the carbonyl carbon. This facilitates the successive attack nucleophilic of alcohol at the position to form a tetrahedral intermediate, step determinant of the rate of the reaction. Experimental and theoretical works agreed that this reaction takes place with the formation of a tetrahedral intermediate. In the present theoretical work were investigated the structure and energy of the tetrahedral intermediate of the reaction. Geometries of all species involved in the acetylation were made and identified. All of the geometry optimizations were performed and all energies were calculated using the method at the DFT/B3LYP level of theory and the MP2 method. Was adopted the 6-31+G* basis set. Following the same procedure it was identified the geometric parameters and energy of reaction intermediate. The calculations show 13.68 kcal/mol of activation energy for the reaction using the DFT method, which reported the lower energy values