Theoretical study on the reaction mechanism of +SCX (X=O, S).

Abstract: Ab initio calculations of the two title reactions have been made to compare reactivities of OCS and CS₂ toward a nucleophile, . MP2/6-311++G(d, p) geometry optimizations on the singlet potential energy surface have demonstrated that respective channels start from key intermediates and have revealed that multistep paths give the most favorable products: (1) +OCS→H₂NS⁻ +CO; (2) +OCS→HS⁻ +HNCO; (3) +OCS→NCS⁻ +H₂O; (4) +OCS→NCO⁻ +H₂S; (5) +CS₂ →NCS⁻ +H₂S; (6) +CS₂ →HS⁻ +HNCS. Furthermore, to get more reliable energetic data, single-point calculations are carried out at CCSD/6-311++G(d, p) level. The calculated result is consistent with the measured large rate constant in experiment. A comparison of reaction mechanisms is offered between +OCS and +CS₂. [ABSTRACT FROM AUTHOR]