Acetalization of 2-Hydroxybenzaldehyde mechanism using halogen acid catalysts based on ab initio methods

The computational calculation was performed on the acetalization of 2-hydroxybenzaldehyde by using ab initio method. Ab initio method is derived directly from theoretical principles with no inclusion of experimental data and this is an approximate quantum mechanical calculation. The aim of this research was to studies the acetalization of 2-hydroxybenzaldehyde mechanism using halogen acid catalysts. Computational calculation which was applied on the acetalization of 2-hydroxybenzaldehyde using halogen acid catalysts provided possible reaction steps. The first step was formation of a labile hemiacetal because it is essentially tetrahedral intermediates containing a leaving group. The second step was formation of a stable acetal. The results of computational calculation of acetalization of 2-hydroxybenzaldehyde provided possible energy change in the each step of the reaction process. A labile hemiacetal showed higher energy (481.04 kJ/mol) than 2-hydroxybenzaldehyde dimethyl acetal (65.32 kJ/mol) and 2-hydroxybenzaldehyde (0 kJ/mol) due to its instability. In general, acetalization of 2-hydroxybenzaldehyde reaction is a reversible reaction. The effect of Lewis acidity on halogen acid catalysts was also studied in this research. Based on the Mulliken charge on the H atom, it is found that HF has the highest Lewis acidity compared to other halogen acids with order HF> HCl> HBr> HI. As a result, HF was the efficient catalysts for acetalization of 2-Hydroxybenzaldehyde.