A Spectroscopic Study of the Folding Propensities of Molecules Relevant in Combustion Processes

Dan Malcolm Hewett, Purdue University

Abstract

This thesis focuses on the conformational preferences of molecules relevant in combustion, specifically alkylbenzenes, present in diesel fuels, and covalently-bound naphthalene dimers, likely intermediates in the soot formation process. Utilizing a suite of conformation-specific laser techniques, coupled with a supersonic jet expansion to cool the molecules down to their ground state zero-point vibrational level, the infrared and ultraviolet spectra of individual conformers are collected and compared to theoretical predictions, resulting in conformational assignments. The first section of this thesis discusses a series of straight chain alkylbenzenes, from ethylbenzene through dodecylbenzene, with the primary goal of determining the shortest chain length at which the alkyl chain folds back over the phenyl ring. The ultraviolet and infrared alkyl CH stretch spectra were collected and compared with calculations, both harmonic energy calculations and infrared spectra calculated using the local mode Hamiltonian model developed in the Sibert group. The fold was found to occur with a chain length of eight carbon atoms. The second part of this thesis focuses on a set of ethyl-linked naphthalene dimers. These molecules were studied with the purpose of answering a question regarding soot formation: how does soot begin? These dimers were studied using the full set of laser-based techniques available in the Zwier lab, and potential evidence of stacked structures was discovered.

Degree

Ph.D.

Advisors

Zwier, Purdue University.

Subject Area

Physical chemistry

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