Quenching and reduction of photoexcited benzophenone by thioethers and mercaptans

Joseph Guttenplan, Saul G. Cohen

Research output: Contribution to journalArticle

Abstract

Reactions of thioethers (sulfides) with excited triplet benzophenones have been studied (1) by retardation by the sulfides of photoreduction by isoborneol, (2) by quenching by naphthalene of photoreduction by the sulfides, and (3) by quenching of phosphorescence of the ketone by the sulfides. Quenching rate constants, kir, are in the range 107-109 M-1 sec-1. They are highest for aliphatic and lowest for aromatic sulfides, and values are decreased by α branching and by electronegative substituents, and higher in acetonitrile than in benzene. Benzophenone is photoreduced by sulfides containing α H. Quantum yields are low, φ ∼ 0.05-0.2, and increase with decreasing values of kir. Quenching of phosphorescence of benzophenone by mercaptans shows values of kq in the range 107-109 M-1 sec-1, highest for aromatic, lowest for aliphatic thiols, decreased by electron-attracting substituents. Reversible hydrogen abstraction is not important in reactions of sulfides, while probably dominant in reactions of thiols. Quenching and photoreduction by sulfides may proceed via a common charge transfer complex, in which a full unit of charge separation is not developed. Contributions of charge transfer, hydrogen transfer, and polarizability in quenching and reduction of excited carbonyl compounds by alcohols, ethers, amines, sulfides, and mercaptans are discussed.

Original languageEnglish (US)
Pages (from-to)2001-2007
Number of pages7
JournalJournal of Organic Chemistry
Volume38
Issue number11
StatePublished - 1973

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Sulfides
Sulfhydryl Compounds
Quenching
Phosphorescence
Charge transfer
Hydrogen
Benzophenones
benzophenone
Carbonyl compounds
Ethers
Quantum yield
Benzene
Ketones
Amines
Rate constants
Alcohols
Electrons

ASJC Scopus subject areas

  • Organic Chemistry

Cite this

Quenching and reduction of photoexcited benzophenone by thioethers and mercaptans. / Guttenplan, Joseph; Cohen, Saul G.

In: Journal of Organic Chemistry, Vol. 38, No. 11, 1973, p. 2001-2007.

Research output: Contribution to journalArticle

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