Date of Award

Summer 2003

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Chemical Engineering - (Ph.D.)

Department

Chemical Engineering

First Advisor

Joseph W. Bozzelli

Second Advisor

Tamara M. Gund

Third Advisor

Dana E. Knox

Fourth Advisor

Michael Chien-Yueh Huang

Fifth Advisor

Edward Robert Ritter

Abstract

Thermochemical properties for reactants, intermediates, products and transition states important in the radicals of acetaldehyde + O2 and allyl radical + O2 reaction systems are analyzed with density functional and ab initic calculations, to evaluate the reaction paths and kinetics in oxidation and pyrolysis. Ketene is one important product resulting from acetaldehyde oxidation; thus thermochemistry plus isomerization and conversion reactions of ketene are also analyzed. Enthalpies of formation are determined using isodesmic reaction analysis at the CBSQ composite and density functional levels. Entropies and heat capacities are determined using geometric parameters and vibration frequencies obtained at the HF/6-31G(d’) or B3LYP/6-31G(d,p) level of theory. Internal rotor contributions are included in calculation of entropy, S°298, and heat capacities, Cp(T). Rate constants are estimated as a function of pressure and temperature using multifrequency quantum Rice-Ramsperger-Kassel analysis for k(E) and master equation analysis for falloff. A mechanism for pyrolysis and oxidation of acetaldehyde and its’ corresponding radicals is constructed. The competition between reactions of radicals of acetaldehyde with O2 versus unimolecular decomposition is evaluated versus temperature and pressure.

Thermodynamic parameters, enthalpies, entropies and heat capacities are evaluated for C1 and C2 chlorocarbon molecules and radicals. These thermodynamic properties are used in evaluation and comparison of Cl2 + R. <--> Cl. + RCl reaction rate constants from the kinetics literature for comparison with empirical analysis. Data from some 20 reactions in the literature show linearity on a plot of Eafwd vs Δrxn, fwd, yielding a slope of (0.38 ± 0.04) and an intercept of (10.12 ± 0.81) kcal/mol.

The use of Density Functional Theory, B3LYP/6-31g(d,p), with isodesmic working reactions for enthalpy of formation of sulfur hydrocarbons is evaluated using a set of known sulfur hydrocarbon / radical species. Thermodynamic and kinetic parameters for reactants, transition states, and products from unimolecular dissociations of sulfur species related to the chemical agent: CH3CH2SCH2CH2, CH3CH2SCH2CH2Cl, and CH2ClCH2SCH2CH2Cl and corresponding radicals are analyzed. Standard enthalpy, ΔHf°298, for the molecules and radicals are determined using isodesmic reaction analysis at the B3LYP/6-31G(d,p) level, with S°298 and Cp(T) determined using geometric parameters and vibrational frequencies obtained at this same level of theory. Potential barriers for the internal rotor potentials are also calculated at the B3LYP/6-31G(d,p) level, and the hindered rotation contributions to S°298 and Cp(T) are calculated.

Share

COinS