Gas Phase Studies of Hydrocarbon Oxidation by Chromium Oxide Cation

Citation

Kang, Heon (1986) Gas Phase Studies of Hydrocarbon Oxidation by Chromium Oxide Cation. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/M9HQ-9749. https://resolver.caltech.edu/CaltechTHESIS:07262010-154826937

Abstract

An ion beam reactive scattering technique is used to study organometallic reactions in the gas phase. Detailed investigations of the reactions of CrO⁺ with hydrocarbons are reported. CrO⁺ formed by surface ionization oxidizes both alkenes and alkanes larger than methane with a high degree of selectivity compared with other first-row transition metal oxides. Analyses of reaction energetics are facilitated by determination of ancillary thermochemical data, including Cr⁺-O and CrO⁺-H bond dissociation energies.

Chapter II presents an analysis of the reactions of CrO⁺ with alkenes. Major reaction channels include allylic hydrogen abstraction by CrO⁺ and oxidative cleavage of double bonds to form aldehydes and smaller alkenes.

Chapter III describes selective oxidation of saturated hydrocarbons by CrO⁺. Major product channels include alcohol formation, dehydrogenation, and loss of alkanes and alkenes. Reaction intermediates in which alkyl C-H bonds add across the Cr⁺-O bond are proposed.

Chapter IV presents studies of reactions of transition metal ions (Ti, V, Cr, Fe, Co, and Ni) with organosilanes in the gas phase. These reactions often lead to formation of metal silylenes as major products. An examination of reaction thermochemistry provides estimates for metal-silylene bond dissociation energies. Relationships between the reactivities, metal-silylene bond energies, and the electronic structures of the metal ions are discussed.

Chapter V describes a novel source which generates metal atom and ion beams by focusing a CO₂ TEA laser onto a solid metal target. Kinetic energy distributions of laser-generated atoms and atomic ions are measured using time-of-flight techniques. Possible mechanisms for the metal ion production as well as aspects of employing the laser-generated beams for gas phase reaction studies are discussed.

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