Quantum mechanical study on the kinetics and thermodynamics of O-alkyl S-methyl dithiocarbonates through α-and β-elimination pathways

The study of αand β-elimination pathways through pyrolysis on the kinetics and thermodynamics of O-alkyl S-methyl Xanthates in which the alkyl groups are ethyl, n-propyl, i-propyl, n-butyl, i-butyl and t-butyl were carried out in the gas-phase using density functional theory (DFT) with B3LYP at 6-311++G** using Spartan. The mechanism proceeded through a six-centered cyclic transition state. The result obtained for the C-H, C-O and S-H bond lengthening character in a single step suggested that the reaction is a concerted and asynchronous. The energy of formation for the α–elimination pathways is lower compared to the β-elimination initiated from the hydrogen of the βcarbon. The activation parameters obtained for the β-elimination pathways ranged from ∆H* (161.34-133.87 kJ/mol), ∆S* (-31.18-25.65 J/mol/K), ∆G* (180.65-149.77 kJ/mol) Ea (166.49-136.82 kJ/mol), k =1.14·10-6.0·10S), A (3.06·10-5.89·10). In addition, α-elimination pathway activation Quantum mechanical study on the kinetics and thermodynamics of O-alkyl S-methyl dithiocarbonates through αand β-elimination pathways Oluwaseun T. ESAN, Isaiah A. ADEJORO, Babatunde T. OGUNYEMI, Oluwatoba E. OYENEYIN 2 parameters for ipropyl and tbutyl are in good agreement with the experimental values.