Publication Date

1981

Document Type

Dissertation/Thesis

First Advisor

Kevill, Dennis N.

Degree Name

M.S. (Master of Science)

Department

Department of Chemistry

LCSH

Chemical kinetics||Solvolysis||Solvents||Organosulphur compounds

Abstract

The N̲[sub KL] scale of solvent nucleophilicity introduced by Kevill and Lin, based on the solvolysis of triethyloxo- nium (Et₃O⁺) ion, was established using the modified form of the extended (four-parameter) Grunwald-Winstein equation: N̲[sub KL] = log (k/kₒ)[sub Et₃O⁺] - 0.55Y⁺ where k is the solvolysis rate constant for any substrate reacting in S[sub N]1 mechanisms in any solvent relative to its rate, kₒ, in 80% aqueous-ethanol as the standard solvent. The Y⁺ values-modified solvent influence on leaving group parameters for charged substrates were obtained from a study of the solvolysis of t-butyldimethylsulfonium (t-BuMe₂S⁺) ions. Although some of the Y⁺ values could be obtained from previous experimental data, other Y⁺ values were estimated from: Y⁺ -0.09Y. The proportionality factor used was obtained from slope of log (k/kₒ)[sub t-BuMe₂S⁺] vs. the Y[sub t-BuCl] values. In view of the irregularity demonstrated by acetic acid in this plot, the present study was carried out to determine the Y⁺ values for aqueous-dioxane, aqueous-2,2,2-trifluoroethanol (TFE), acetic acid, ethanol (EtOH)-2,2,2-trifluoroethanol, formic acid, isopropyl alcohol and tert-butyl alcohol. These values were then used to recalculate new N̲[sub KL] values. It was also necessary to carry out solvolysis for triethyloxonium ions in ethanol-2,2,2-trifluoroethanol mixed solvent system, for no such studies were carried out before. The first order rate constants for the solvolysis of various t-butyldimethylsulfonium salts were found to be essentially independent of the anion. Using the trifluorome-thanesulfonate salt as the standard, in 80% ethanol, the iodide reacted 19% faster and for antimonate, it is 29% faster. From the solvolysis of t-butyldimethylsulfonium ions, m̲ values for various solvents and mixed solvents can be calculated from the plot of log (k/kₒ)[sub t-BuMe₂S⁺] vs. the Y values based on t-butyl chloride (t-BuCl) solvolysis. For a range of 90% dioxane to 20% dioxane (aqueous-dioxane) m̲ = -0.039, 100% 2,2,2-trifluoroethanol to 20% 2,2,2-trifluoroethanol (in aqueous mixture) m̲ = 0.220 and for 100% 2,2,2-trifluoroethanol to 100% ethanol (in TFE-EtOH mixed solvent) m̲ = -0.250. The N[sub KL] obtained for R-X⁺ systems in this work were then compared to N values for R-X systems, and are found to be in fairly good agreement.

Comments

Includes bibliographical references.||Includes illustrations.

Extent

xiii, 95 pages

Language

eng

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

Media Type

Text

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