Bimolecular elimination reactions in the gas phase : an ion cyclotron resonance spectrometric study

Author

Terry Lynn Sumpter

Date of Award

8-1990

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Chemistry

Major Professor

John E. Bartmess

Abstract

This work examines the reactivity of a variety of compounds toward bimolecular elimination reactions in the gas phase. Several different systems have been examined, and the effects of varying the nature of the reactive site, the leaving group, and the attacking base have been investigated. A series of 2-substituted chloroethanes have been allowed to react with methanethiolate. For most of the compounds of this series, direct interaction between the substituent and the reactive site of the substrate is precluded by the presence of an intervening methylene group. It is found that a twenty-fold increase in the rate of production of chloride is obtained from the series of substrates of nearly the same acidity. The observed reactivity is best described using a dual-substituent parameter (DSP) relationship which incorporates both the inductive substituent constant σ_I of the substituent and the isotropic polarizability α of the CH₃-G molecule. A series of 2-substituted ethyl methyl ethers were allowed to react with anionic bases. In this study, the substituent is capable of direct interaction with the reactive site of the substrate. A pattern of reactivity is seen in which the primary processes of proton abstraction and loss of methoxide are in competition with a variety of secondary and other reactions. The main reaction pathways observed are proton transfer, formation of vinyl anions, hydride transfer to α, β-unsaturated carbonyl neutral products, and Michael-type reactions involving the reaction of the vinyl anions formed with neutral substrate molecules. Rate constants are reported for these reactions. A series of substituted phenethyl methyl ethers were allowed to react with anionic bases. In contrast to the substituted ethyl methyl ethers, the pattern of reactivity in this case consisted primarily of loss of methoxide, both free and clustered with the attacking base, and a secondary reaction involving the attack of initially formed methoxide upon the neutral substrate. Rate constants are reported for these processes. Leaving-group effects are investigated using a series of phenethyl ethers. Loss of both free and clustered leaving group is observed, as well as some competing reactions. Rate constants are reported for these reactions.

Recommended Citation

Sumpter, Terry Lynn, "Bimolecular elimination reactions in the gas phase : an ion cyclotron resonance spectrometric study. " PhD diss., University of Tennessee, 1990.
https://trace.tennessee.edu/utk_graddiss/11512