Theoretical study of the internal elimination reactions of xanthate precursors

Abstract

The gas-phase internal elimination (E(i)) reaction of ethyl xanthate (CH(3)-CH(2)-S-CS-O-CH(3)) has been investigated by means of Hartree-Fock, second-order Møller-Plesset, and density functional theory (DFT) using the Becke three-parameter Lee-Yang-Parr (B3LYP) functional and the modified Perdew-Wang one-parameter model for kinetics (MPW1K). Considerable differences between the ground- and transition-state geometries and the calculated activation energies are observed from one approach to the other, which justifies first a careful calibration of the methods against the results of benchmark CCSD(T) calculations. Compared with these, DFT calculations along with the MPW1K functional are found to be an appropriate choice for describing the E(i) reaction of xanthate precursors. The precursor conformation and the transition states involved in the internal conversion of xanthate precursors of cyano derivatives of ethylene, and of cis- and trans-stilbene, are then characterized in detail by means of this functional.

Development and Assessment of a New Hybrid Density Functional Model for Thermochemical Kinetics

“…MPW1K is the modified Perdew-Wang-1-parameter model for kinetics based on the mPW1PW91 5 model, but with the percentage of Hartree−Fock exchange optimized against a kinetics database including 20 reactions . Several studies − have demonstrated that the MPW1K model gives remarkably good performance for kinetics.…”

Evaluation of Functionals O3LYP, KMLYP, and MPW1K in Comparison to B3LYP for Selected Transition-Metal Compounds

“…It uses the modified Perdew-Wang gradient-corrected exchange functional and the correlation functionals of Adamo and Barone . Comparing MPW1K to B3LYP, it is notable that it includes a larger proportion of the HF 9 exchange functional. ,, It was shown that geometries and vibrational frequencies of stationary points, enthalpies, and barrier heights for organic reactions obtained with the MPW1K method are in good agreement with experimental values or with higher order calculations. ,,,− MPW1K is claimed to be especially superior to other DFT methods for the calculation of large systems . Li et al investigated several hydrogen atom transfer reactions involved in atmospherical chemistry with hybrid DFT methods.…”

“…30,32,33 It was shown that geometries and vibrational frequencies of stationary points, enthalpies, and barrier heights for organic reactions obtained with the MPW1K method are in good agreement with experimental values or with higher order calculations. 19,29,30,[32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48] MPW1K is claimed to be especially superior to other DFT methods for the calculation of large systems. 35 Li et al 37 investigated several hydrogen atom transfer reactions involved in atmospherical chemistry with hybrid DFT methods.…”

Reaction mechanisms and kinetics of the elimination processes of 2-chloroethylsilane and derivatives: A DFT study using CTST, RRKM, and BET theories

“…The obtained results in the previous study need to be verified using more reliable exchange-correlation functionals and basis set. Due to the self-interaction error of commonly used B3LYP functional [25], transition barriers obtained with the B3LYP energy functional are usually strongly underestimated [26,27].…”