Sharif Digital Repository

For the first time, the mechanism of Fischer esterification between acetic acid and ethanol over silica-functionalized propylsulfonic acid (silica-propyl-SO3H) catalyst was explored by means of computational modeling techniques. For this purpose, 6-edge-atom cage-like cluster comprising Si-O-Si sequences has been selected to represent the surface of the catalyst. The results indicate that the reaction goes through concerted transition states. In all optimized structures no proton (H+) transfer occurs from catalyst to the substrates and the role of the catalyst is via the activation of the substrates through the formation of strong hydrogen bonds (H-bonds). Furthermore, the energetic diagram... 

A task-specific Brønsted acidic ionic liquid (BAIL), 1-benzyl-3-methylimidazolium hydrogensulfate ([BnMIm]HSO4), was prepared and confined onto the high surface area silica gel. The catalyst has shown extraordinary activity in comparison of homogeneous ionic liquid (IL) system for Fischer esterification of fatty acid with ethanol. The ester derivatives were synthesized in high yields and catalyst was easily separated from the reaction mixture by simple filtration. The structure of the catalyst is theoretically modelized to investigate the unusual catalytic activity. Hence, a hydroxylated cage-like nano-cluster, H6Si8O12(OH)2, was selected to mimic the surface of silica gel. The interactions...