Date of Award

Summer 2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Environmental Science - (Ph.D.)

Department

Chemistry and Environmental Science

First Advisor

Joseph W. Bozzelli

Second Advisor

Tamara M. Gund

Third Advisor

Nancy L. Jackson

Fourth Advisor

Alexei Khalizov

Fifth Advisor

Yogesh V. Joshi

Abstract

Thermochemical and transport properties and reaction kinetic parameters are important to understand and to model atmospheric chemistry, combustion and other thermal systems. These processes are all important to the environment. Thermochemical properties kinetic parameters and models for several atmospheric and combustion related chemical systems are determined using computational chemistry coupled with fundamentals of thermodynamics and statistical mechanics. Transport properties of hydrocarbon and oxygenated hydrocarbons which are important to the calculation of fluid dynamics of gas phase flow reactions and mixing needed for evaluation in the combustion and thermal (flow) fluid dynamic modeling. Transport properties of radicals cannot be measured so computational chemistry is method of choice. The dissertation determine dipole moment, polarizability and molecular diameters of hydrocarbon and oxygenated hydrocarbons needed for calculation of multicomponent viscosities, thermal conductivities, and thermal diffusion coefficients.

Cyclopentadienone with cyclic five-member ring aromatic structure is an important intermediate in combustion systems. Thermochemical and kinetic parameters for the initial reactions of cyclopentadienone radicals with O2 and the thermochemical properties for cyclopentadienone - hydroperoxides, alcohols, alkenyl , alkoxy and peroxy radicals are determined by use of computational chemistry via Density Functional Theory (DFT) and the composite, Complete Basis Set (CBS) methods. Enthalpies of formation (Δf298) with the isodesmic reaction schemes with several work reactions for each species are used for standard enthalpies. Entropy and heat capacity, S° (T) and CP° (T) (50 K ≤ T ≤ 5000 K) are also determined. Chemical activation kinetics using quantum RRK analysis for k(E) and master equation for fall-off are used for kinetic parameters and to show significance of chain branching as a function of temperature and pressure. The cyclopentadienone vinylic carbon radicals of with molecular oxygen appear to undergo chain branching via reaction with O2, to a higher extent to that of vinyl and phenyl radicals.

Reaction kinetics of hydrogen atom addition to primary (P), secondary (S), tertiary (T) vinylic (olefin) carbons to form an alkyl radical is investigated using Density Functional Theory (DFT) and ab initio composite level methods. Results from calculations at different levels are compared with the experimental literature data for hydrogen atom addition to Ethylene, Propene, 1-Butene, E-2-Butene, Z-2-Butene, and Isobutene. Activation energy and rate constants for forward and reverse paths are investigated and compared with available experimental data. One goal of the study is to determine accurate calculation method for use on large molecules.

Chlorofluorocarbons are widely present in the environment. Thermochemical and kinetic properties work will aid in the understanding the chlorofluorocarbons reactions in combustion and atmospheric environments. Trifluoroethene (CF2=CHF) reaction in atmospheric and combustion environment initiated via OH radical system is investigated. The HF generated channel is currently not reported in any kinetic study. It is important as the toxic gas that can cause severe respiratory damage in humans.

Share

COinS