Quantum mechanical studies of the kinetics, mechanisms and thermodynamics of gas-phase thermal decomposition of ethyl dithiocarbonate (xanthate)

Abstract

Theoretical studies were carried out to investigate the thermal decomposition of ethyl dithiocarbonates (xanthate) using Hartree-Fock at the HF/321-G* level and the density functional method with Becke 3 Lee Yang pair DFT/(B3LYP), 6-31G*, 6-31G**, 6-31+G*, MP2 and CCSD in the ab initio method of calculation using Spartan 10. Geometric parameters, such as the bond length, bond angles, dihedral angles, heat of formation, atomic charges and vibrational frequencies, were obtained. The data were used to calculate the thermodynamics parameters, change in entropy S, enthalpy change H, free energy G, pre-exponential factor A, rate k at 623 K, and variation of rate k with temperatures from 498-623 K at temperature intervals of 25 K. It was observed that the values obtained are in good agreement with the experimental values for the ab initio methods, and according to Arrhenius theory, the calculated rate k increases with increasing temperature.

Computational modelling Procedures for Geometry Optimization, Kinetic and Thermodynamic Calculations using Spartan Software - A Review

“…This detailed and simple progressive procedure for calculations described using Spartan software has been used for computational modeling of kinetic and thermodynamic [9][10][11][12][13][14][15][16] studies of various reactions.…”

Computational Investigation Into the Kinetics, Mechanism and Thermodynamics Properties of the Gas-Phase Thermal Decomposition of 1-Phenyl Ethyl Acetate

“…Consequently, the use of theoretical methods has become a desirable approach to probe chemical reactions and overcome the disadvantages of trial and error of the experimental approach (Ogunyemi and Bosisade, 2020). A large number of studied unimolecular reactions (thermal decomposition) in the gas phase apparently occurred through 4-and center cyclic activated complexes (Warren Hehre 2003;Blades , 1954;Hurd and Blunck, 1938;Saheb and Hosseini, 2013;Adejoro et al, 2017). The mechanisms of ethyl acetate previously reported show that various pathways for the unimolecular reactions are possible [8][9][10].…”

“…According to experimental reports (Blades 1954), thermal decomposition of 1-phenylethyl acetate proceeds through a concerted six-membered cyclic transition state type of mechanism. The presence of a Cβ-H on the alkyl side of organic esters, such as acetates, leads to elimination through a six-centered cyclic transition type of mechanism (Adejoro and Bamkole, 2005;Esan et al, 2020;Brusco et al, 2009;Adejoro et al,2013). The importance of the breaking of the carbon-hydrogen and carbon-oxygen single bonds aids the formation of olefinic bond stability of ester at higher yield.…”