Theoretical Studies on Nucleophilic Substitution Reactions of Phenyl Thiophosphonyl Isothiocyante with Pyridnes Through Frontal Approach

초록

We have studied phosphoryl and phosphonyl transfer reactions with pyridines, anilines and benzylamins. The phosphoryl transfer systems are proceeded either through concerted or stepwise pathway. There are many examples in the literatures where mechanistic changeover is taking place during the process. Our present study focuses on the mutual interaction of the substituents in the nucleophile and substrate, energy correlation analysis and the cross interaction constant4 (CIC), ρXY. In this work, the reaction mechanism for the pyridinolysis of phenyl thiophosphonyl isothiocyanates are investigated using the CPCM approach in acetonitrile at the B3LYP/6-311+G(d,p) level of theory. We optimized all the reactant complexes, transition states, and product complexes to obtain the potential energy surfaces for seven different substituents of X and Y for nucleophiles and substrates, respectively. Frequency calculations were performed to confirm the stationary species and to provide thermodynamic properties. The reaction mechanism is discussed in terms of Hammett reaction constants, ρX, ρY, and cross interaction constant ρXY and the structure-energy relationships.