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Dissertation
The chemistry of sulfenic acids
Doctor of Philosophy (Ph.D.), Drexel University
1984
DOI:
https://doi.org/10.17918/00008940
Abstract
Sulfenic acids (RSOH) were generated by flash vacuum pyrolysis (FVP) of sulfoxides (RS(O)R) and their relative reactivities were determined by reaction with alkenes and alkynes. Although thiosulfinates (RS(O)SR) are formed in almost all reactions that are believed to involve sulfenic acid intermediates, the ratio of thiosulfinate to trapped adduct can be used as an indication of sulfenic acid reactivity. Using this ratio, it was determined that substituents capable of forming hydrogen bonds placed ortho to an aromatic sulfenic acid afforded an increase in sulfenic acid stability. It was also determined that ortho substituents with active hydrogens (e.g. OH, CH(,2)OH) provided no stabilizing effect. The importance of six- versus a seven-membered hydrogen bonded ring for the stabilization of sulfenic acids is also discussed. Attempts to stabilize aromatic sulfenic acids were performed by placing large substituents at the 2- and 6-positions; however, these sulfenic acids could be neither isolated nor detected. Such is the case of 2,4,6-trineopentylbenzenesulfenic acid, which upon generation by FVP produced 2-tert-butyl-4,6-dineopentylbenzo[b]thiete, as the major product. This represents a novel reaction of sulfenic acids, namely 1,4 dehydration. Using a modified FVP, in which the cold finger condenser was replaced with a cryo-tip equipped with NaCl windows, the IR of sulfenic acids could be obtained. By using this apparatus, it has been demonstrated that sulfenic acids exist in two tautomeric forms at low temperatures. However, at temperatures above -70(DEGREES)C, sulfenic acids tend to favor the O-protonated form. By using 2-arenesulfonyl-3-aryloxaziridines in the oxidation of thiols, it was possible to demonstrate for the first time the existence of 2-methyl-2-propanesulfenic acid, generated by oxidation of 2-methyl-2-propanethiol and trapped with methyl propiolate. The "(alpha)-effect" nucleophilicity of sulfenic acids was qualitatively demonstrated in the oxidation of 2-methyl-2-propane, (alpha)-toluene-, benzene- and p-fluorobenzenethiols. The mechanism for oxidation and reactions of the resulting sulfenic acids were determined by NMR (('1)H, ('13)C, ('19)F).
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Details
- Title
- The chemistry of sulfenic acids
- Creators
- Robert Lee Billmers
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xiv, 178 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- College of Science (1970-1990); Drexel University
- Other Identifier
- 991021888828904721