Structural and thermochemical properties of methyl ethyl sulfide alcohols: HOCH₂SCH₂CH₃, CH₃SCH(OH)CH₃, CH₃SCH₂CH₂OH, and radicals corresponding to loss of H atom

Abstract

Sulfide alkoxy radicals are important intermediates during the partial oxidation of alkyl sulfides in atmospheric chemistry and in combustion. The atmospheric reaction sequence to formation of the alkoxy radicals includes (1) initial reaction with OH to create a radical on a carbon site, (2) the carbon radical then associates with 3 O 2 to form a peroxy radical, and (3) an NO radical reacts with the peroxy radical to form an alkoxy radical (RO•) plus NO 2 . This study determines structural parameters, internal rotor potentials, bond dissociation energies, and thermochemical properties (Δ f H°, S°, and C p (T)) of 3 corresponding alcohols HOCH 2 SCH 2 CH 3 , CH 3 SCH(OH)CH 3 , and CH 3 SCH 2 CH 2 OH of methyl ethyl sulfides studied in order to characterize the thermochemistry of the respective alkoxy radicals. The lowest energy molecular structures were calculated using the B3LYP density functional level of theory with the 6-311G(2d,d,p) basis set. Standard enthalpies of formation (Δ f H°2 98 ) for the radicals and their parent molecules were calculated using B3LYP/6-31 + G(2d,p), CBS-QB3, M062x/6-311 + g(2d,p), and G3MP2B3 methods. Isodesmic reactions were used to determine Δ f H°values. Internal rotation potential energy diagrams and rotation barriers were investigated using the B3LYP/6-31 + G(d,p) level theory. The contributions for S°2 98 and C p (T) were calculated using the rigid rotor harmonic oscillator approximation based on the structures and vibrational frequencies obtained by CBS-QB3 calculations, with contributions from torsion frequencies replaced by internal rotor contributions. Group additivity and hydrogen bond increment values were developed for estimating properties of structurally similar and larger sulfur-containing peroxide molecules and their radicals.

Probing the Chemistry of Sulfurous Pollutants: Accurate Thermochemistry Determination of Extensive Sulfur-Containing Species

“…Thermochemistry is an essential physical and chemical property for the essential chemical transformation of species such as combustion, pyrolysis, and catalysis. Previous studies − have reported the enthalpies of formation at 298 K for some sulfur-related compounds, as shown in Table . Nagy et al also calculated the entropy values of HSO, HOS, HOSO 2 , HSNO, SH, CH 2 SO, CH 2 SH, S 2 COH, and SCSOH.…”

Heat Capacity Estimation Using a Complete Set of Homodesmotic Reactions for Organic Compounds

“…Thus, in the 21st century, more than 500 scientific materials have been published that use the concept of homodesmoticity to obtain various types of thermochemical information. It may provide few illustrative examples of recent publications using the homodesmotic method for calculating the enthalpy characteristics of organic molecules and radicals [8][9][10][11][12][13][14][15][16], quantitative description of aromaticity [17][18][19], determination of strain energies in cyclic structures and compounds of a complex structure [20][21][22][23][24][25][26][27]. As with additive approaches, the homodesmotic method Molecules 2022, 27, 7814 2 of 15 is convenient for the algorithmization and application of computational technologies in thermochemical analysis [28][29][30][31][32][33].…”