Oxidation of (carboxyalkyl)thiopropionic acid derivatives by hydroxyl radicals. Mechanisms and kinetics of competitive inter- and intramolecular formation of {sigma}- and {sigma}{sup *}-type sulfuranyl radicals
- Inst. of Nuclear Chemistry and Technology, Warsaw (Poland)
- Univ. of Kansas, Lawrence, KS (United States). Dept. of Pharmaceutical Chemistry
The substituent effects on kinetics and yields of specific intermediates and products for the one-electron oxidation by hydroxyl radicals of various (carboxyalkyl)thiopropionic acid derivatives, 3-(methylthio)propionic acid (3-MTPA), 3,3{prime}-thiodipropionic acid (3,3{prime}-TDPA), 3-(carboxymethylthio)propionic acid (3-CMTPA), and 2-(carboxymethylthio)succinic acid (2-CMTPA) have been investigated employing pulse radiolysis on the nanosecond to microsecond time scale, and {gamma}-radiolysis. For each derivative, the initial step was a formation of a hydroxysulfuranyl radical proceeding with absolute rate constants of k{sub OH+3-MTPA} = 9.1 {times} 10{sup 9} M{sup {minus}1}s {sup {minus}1} and k{sub OH+3,3{prime}-TDPA} = 5.8 {times} 10{sup 9} M{sup {minus}1} s{sup {minus}1}. The subsequent formation of one-electron-oxidized intermediates such as dimeric sulfur-sulfur (S{hor_ellipsis}S)-three-electron-bonded and monomeric sulfur-carboxylate oxygen (S-O)-bonded sulfide radical cations strongly depended on pH, thioether concentration, and the availability of {alpha} or {beta}-positioned carboxylate functions. A spectral resolution procedure permitted the quantification of all transients present in solution at any time after the pulse.
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- OSTI ID:
- 316000
- Journal Information:
- Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory, Journal Name: Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory Journal Issue: 51 Vol. 102; ISSN 1089-5639; ISSN JPCAFH
- Country of Publication:
- United States
- Language:
- English
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