Thermochemical properties of small oxygenated sulfur hydrocarbons and kinetics - reaction pathways of methylthiomethyl radical with oxygen

Author

Fei Jin, New Jersey Institute of Technology

Document Type

Thesis

Date of Award

Fall 1-31-2004

Degree Name

Master of Science in Applied Chemistry - (M.S.)

Department

Chemistry and Environmental Science

First Advisor

Joseph W. Bozzelli

Second Advisor

Lev N. Krasnoperov

Third Advisor

Tamara M. Gund

Abstract

The thermochemical properties on CH₃SCH₂OOH and the corresponding two radicals resulting from loss of H atom: CH₃SCH₂OO and CH₂SCH₂OOH are important to understand the stability, reaction paths and kinetics of reactions of dimethyl sulfide and other sulfur hydrocarbons (sulfides) in the atmosphere and combustion processes. Thermochemical properties for species and transition states in the methylthiomethyl radical (CH₃SCH₂) + O₂ reaction system are analyzed to evaluate reaction paths and kinetics under these conditions. Isodesmic working reaction are employed to determine the enthalpies of formation (ΔH_f°₂₉₈) using density functional (B3LYP/6-3 1 1G(d,p)) and complete basis set extrapolation (CBS-QB3) computational methods. Entropy (S°₂₉₈) and heat capacities C_P(T) ( 300≤T/K≤1500) are determined using geometric parameters and vibration frequencies obtained at B3LYP/6-3 11 G(d,p) level of calculation. Quantum Rice-Ramsperger-Kassel(QRRK) analysis is used to calculate energy- dependent rate constants, k(E) and master equation is used to account for collisional stabilization of adduct and isomer. The methyithiomethyl radical adds to oxygen to form a methylperoxy racial with a 37.82 kcal/mol well depth. The peroxy radical can undergo dissociation back to reactants, isomerize via hydrogen shift (TS1, E_a=17.06kcal/mol) to form a hydroperoxide methyl radical CH₂SCH₂OOH, decompose via hydrogen transfer (TS2, E_a=37.79kcal/mol) to form CH₃SC(=O)H plus OH radical , or the peroxy radical can also attack the sulfur atom via TS3 (E_a=32.92kcal/mol) to form CH₃S(=O) + CH₂O. The CH₂SCH₂OOH isomer can decompose via TS4 (E_a=24.O9kcal/mol) to form CH₂O+CH₂S+OH, or through a four-member ring transition state (TS5, E_a= 30.77kcal/mol) to form 1,3-Oxathietane + OH.

Structures and thermochemical properties on Sulfenic Acids (RSOH R = CH₃, CH₃CH₂, CH₂=CH,) and their radicals are determined by CBS-QB3 calculation. Molecular structures and vibration frequencies are calculated at B3LYP/6-311G(d,p) levels. ΔH_F°298, S°₂₉₈ and C(T) for the concerned species are calculated in this study. Enthalpies of formation are determined using the ΔH°_rxn(298) and known enthalpies in each of different working reactions. Contributions to entropy and heat capacity from internal rotation are also determined.

Recommended Citation

Jin, Fei, "Thermochemical properties of small oxygenated sulfur hydrocarbons and kinetics - reaction pathways of methylthiomethyl radical with oxygen" (2004). Theses. 586.
https://digitalcommons.njit.edu/theses/586