Theoretical Studies on the Bimolecular Nucleophilic Substitution Reactions for Y-substituted Benzene Sulphonyl Isothiocyanate

초록

The kinetics and mechanism of the pyridinolysis (XC5H4N) of Y-substituted benzene sulphonyl isothiocyanate (Y-C6H4O(S(=O)2)NCS) in acetonitrile are investigated at room temperature at 25.0℃. Physical and thermodynamic parameters as well as molecular orbital overlapping indicate both the front and rear-side nucleophilic attack of pyridines and leaving group (-NCS) departure strategies. According to the literature and several experimental evidences, concerted or a stepwise mechanistic route during the expulsion of isothiocyanate (NCS) leaving group from the intermediate or TS is possible, where positive and negative ρX, and βX values including thermodynamic parameters imply the characteristics of the nucleophilic attack. In addition, the steric effects of the ligands and two S=O orbital inflation can play an important role in determining the rates of the reactions