Laser flash photolysis studies of aroyl xanthates and carboxylic dithiocarbamic anhydrides

Weir, D. ; Ajayaghosh, A. ; Muneer, M. ; George, M. V. (1990) Laser flash photolysis studies of aroyl xanthates and carboxylic dithiocarbamic anhydrides Journal of Photochemistry and Photobiology A: Chemistry, 52 (3). pp. 425-437. ISSN 1010-6030

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Official URL: http://linkinghub.elsevier.com/retrieve/pii/101060...

Related URL: http://dx.doi.org/10.1016/1010-6030(90)85020-W

Abstract

Results of a photochemical study based on nanosecond laser flash photolysis of some representative aroyl xanthates and carboxylic dithio carbamic anhydrides (1b, 9a - 9d) are presented. The 266 nm or 308 nm laser pulse excitation of the substrates in acetonitrile produces radical intermediates, arising through C(=O)---S and C(=S)---S bond fissions. These intermediates are characterized by their lifetimes, second-order decays and facile quenching by free radical quenchers such as 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO), 4-hydroxy-2,2,6,6-tetramethylpiperidinyl-1-oxyl (HTEMPO) and di-tert-butylnitroxyl (DTBN) (kq = (0.1 - 6) × 109 M-1 s-1). Xanthone triplet is quenched by the substrates at diffusion-controlled rates (k = (1.4 - 4.8) × 1010 M-1 s-1), and results in the same transient radical intermediates as those observed on direct photolysis.

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