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

Document Type

Article

Publication Date

2-1-2018

Abstract

Hydroperoxides and the corresponding peroxy radicals are important intermediates during the partial oxidation of methyl ethyl sulfide (CH3SCH2CH3) in both atmospheric chemistry and in combustion. Structural parameters, internal rotor potentials, bond dissociation energies, and thermochemical properties (ΔHf o, So and Cp(T)) of 3 corresponding hydroperoxides CH2(OOH)SCH2CH3, CH3SCH(OOH)CH3, CH3SCH2CH2OOH of methyl ethyl sulfides, and the radicals formed via loss of a hydrogen atom are important to understanding the oxidation reactions of MES. The lowest energy molecular structures were identified using the density functional B3LYP/6-311G(2d,d,p) level of theory. Standard enthalpies of formation (ΔHf o 298) for the radicals and their parent molecules were calculated using the density functional B3LYP/6-31G(d,p), B3LYP/6-31 + G(2d,p), and the composite CBS-QB3 ab initio methods. Isodesmic reactions were used to determine ∆Hf o values. Internal rotation potential energy diagrams and rotation barriers were investigated using the B3LYP/6-31G(d,p) level theory. Contributions for So 298 and Cp(T) were calculated using the rigid rotor harmonic oscillator approximation based on the structures and vibrational frequencies obtained by the density functional calculations, with contributions from torsion frequencies replaced by internal rotor contributions. The recommended values for enthalpies of formation of the most stable conformers of CH3SCH2CH2, CH2(OOH)SCH2CH3, CH3SCH(OOH)CH3, and CH3SCH2CH2OOH are −14.0, −33.0, −37.2, and −32.7 kcal/mol, respectively. Group additivity values were developed for estimating properties of structurally similar and larger sulfur-containing peroxides. Groups for use in group additivity estimation of sulfur peroxide thermochemical properties were developed.

Identifier

85040716377 (Scopus)

Publication Title

Journal of Physical Organic Chemistry

External Full Text Location

https://doi.org/10.1002/poc.3751

e-ISSN

10991395

ISSN

08943230

Issue

2

Volume

31

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