A kinetic and thermochemical database for organic sulfur and oxygen compounds

Abstract

Potential energy surfaces and reaction kinetics were calculated for 40 reactions involving sulfur and oxygen. This includes 11 H2O addition, 8 H2S addition, 11 hydrogen abstraction, 7 beta scission, and 3 elementary tautomerization reactions, which are potentially relevant in the combustion and desulfurization of sulfur compounds found in various fuel sources. Geometry optimizations and frequencies were calculated for reactants and transition states using B3LYP/CBSB7, and potential energies were calculated using CBS-QB3 and CCSD(T)-F12a/VTZ-F12. Rate coefficients were calculated using conventional transition state theory, with corrections for internal rotations and tunneling. Additionally, thermochemical parameters were calculated for each of the compounds involved in these reactions. With few exceptions, rate parameters calculated using the two potential energy methods agreed reasonably, with calculated activation energies differing by less than 5 kJ mol(-1). The computed rate coefficients and thermochemical parameters are expected to be useful for kinetic modeling.

Structures and thermochemistry of methyl ethyl sulfide and its hydroperoxides: HOOCH2SCH2CH3, CH3SCH(OOH)CH3, CH3SCH2CH2OOH, and radicals

“…The scaled vibrations and the moment of inertia are based on the lowest energy structures optimized in the CBS‐QB3 calculation . The scaling factor for zero‐point vibrational energy is 0.99 …”

“…The Benson group additivity method has been widely used for the estimation of thermodynamic properties of hydrocarbons and oxygenated hydrocarbons due to its good relative accuracy and straightforward application . Results from the group additivity method for the species where groups were available in the literature are listed for comparison.…”

“…The hydrogen‐bond increment (HBI) method is used for estimation of the thermochemical properties of radicals formed by removal of 1 H atom from the parent molecules . The hydrogen atom bond increment method developed by Lay et al has been illustrated in previous studies .…”

Reaction kinetics and thermochemistry of the chemically activated and stabilized primary ethyl radical of methyl ethyl sulfide, CH3SCH2CH2•, with O2 to CH3SCH2CH2OO•

“…35,36 The scaling factor for CBS-QB3 level zero-point vibrational energy is 0.99. [35][36][37][38] The internal rotor potentials and the lowest energy optimized conformer for each target, parent peroxide molecule, and radical were determined using the B3LYP/6-31+G(d,p) level DFT calculations. Internal rotor analysis was performed on each C-S, C-C, C-O, or O-O single bond rotors to determine the lowest energy structures.…”

“…where h p is the Planck's constant and к b is Boltzmann's constant, R is gas constant, and R = 1.987 cal mol −1 K −1 . 34,38,49,50 The high-pressure limit rate constant parameters are calculated based on the thermochemical properties of reactant, product, and transition state geometries optimized under the CBS-QB3 level. Temperature-and pressure-dependent rate constants are calculated using the multichannel, multifrequency quantum Rice-Ramsperger-Kassel (QRRK) analysis for k(E) based on a master equation analysis for falloff and stabilization as implemented in the CHEMASTER code.…”