Thermochemical properties, bond energies and internal rotor potentials in methyl ethyl sulfide and oxygenated sulfur hydrocarbons intermediates for modeling its combustion and atmospheric chemistry

Author

Guanghui Song, New Jersey Institute of Technology

Document Type

Thesis

Date of Award

Spring 5-31-2011

Degree Name

Master of Science in Chemical Engineering - (M.S.)

Department

Chemical, Biological and Pharmaceutical Engineering

First Advisor

Joseph W. Bozzelli

Second Advisor

R. P. T. Tomkins

Third Advisor

Tamara M. Gund

Fourth Advisor

Rubik Asatryan

Abstract

Small (1 to 4 carbon) hydrocarbon sulfides and thiols are formed in the biosphere by microorganisms and subsequently emitted into the lithosphere, hydrosphere and atmosphere. In the atmosphere they are oxidized by photochemical and radical reactions to intermediate hydrocarbon and to sulfur oxides. The oxides of these sulfur compounds and the intermediates from the oxidation process are known to form aerosols that can counteract the global warming green house effect. Recent studies also suggest that some aerosols can also contribute to global warming. Sulfur oxides are also major contributors to acid rain as the results of the atmospheric chemistry oxidation reactions on sulfur hydrocarbons and H₂S involve SO₂ formation. It is of great value to understand the thermochemistry and the elementary reaction processes of these sulfur compounds in order to better model atmospheric chemistry and global warming. The oxidation chemistry is also of value in model development for improvement of combustion processes and pollutant reduction. This study determines the structures, internal rotor potentials, bond energies and thermochemical properties (ΔfH°, S° and Cp(T)) of methyl ethyl sulfide (CH₃SCH₂CH3), a widely used sulfuric hydrocarbon, and its main partial oxidation products in the atmosphere (CH₃SCH₂CHO, CH₃CH₂SCHO and CH₃SC(=O)CH₃). At the same time their radicals after losing one H atom, and some of the main partial reaction intermediate molecules and their main radicals after loss of an H atom have also been studied. The molecular structure and H-molecule bond energy are determined using Density Functional B3LYP/6-31G (d,p) and B3LYP/6-31+G(2d,p) together with the higher level composite CBS-QB3. Enthalpies of formation (Hf) for stable species are calculated in the levels of B3LYP/6-31G (d,p), B3LYP/6-31+G(2d,p) and CBS-QB3 using work reactions that are presumed isodesmic. Internal rotation barriers have also been determined with some other DFT methods. Then, thermochemical parameters (S° and Cp(T)) are determined with the help of the Hf values and the data of moments of inertia and frequencies from the CBS-QB3 output files.

Recommended Citation

Song, Guanghui, "Thermochemical properties, bond energies and internal rotor potentials in methyl ethyl sulfide and oxygenated sulfur hydrocarbons intermediates for modeling its combustion and atmospheric chemistry" (2011). Theses. 110.
https://digitalcommons.njit.edu/theses/110