Mechanism of the [sup [lg bullet]]OH radical-induced decarboxylation of 2-(alkylthio)ethanoic acid derivatives

Journal Article · Thu Dec 23 04:00:00 EST 1993 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100153a042· OSTI ID:5115222

Bobrowski, K ^[1]; Pogocki, D ^[2]; Schoeneich, C ^[3]

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1. Univ. of Notre Dame, IN (United States)
2. Inst. of Nuclear Chemistry and Technology, Warsaw (Poland)
3. Univ. of Kansas, Lawrence, KS (United States)

The reactions of the hydroxyl radical with 2-(methylthio)ethanoic acid and 2,2[prime]-thiodiethanoic acid have been investigated in H[sub 2]O and D[sub 2]O. The initial step is a formation of an OH adduct at the sulfur moiety (absorption maximum at [lambda] = 340 nm) with absolute rate constants of k[sub OH+2[minus]MTEA] = 8.7 X 10[sup 9] M[sup [minus]1] s[sup [minus]1] and k[sub OH+2.2[prime][minus]TDEA] = 9.1 X 10[sup 9] M[sup [minus]1] s[sup [minus]1]. The subsequent decay pathways of these adducts strongly depend on pH but do not lead to the respective intermolecularly S. S-bonded dimeric radical cations even at high concentrations of solute ([approximately] 10[sup [minus]2] M) and protons ([approximately] 10[sup [minus]1] M). The S.S-bonded radical cations are typically formed upon oxidation of unsubstituted thioethers. Instead, very high radiation chemical yields of CO[sub 2] (G = 3.5-6.0) and of [alpha]-(alkylthio)-alkyl radicals are observed over the entire investigated pH region (1.0-7.5). Mechanistically, the formation of CO[sub 2] and the associated reaction kinetics including solvent kinetic isotope effects suggest the occurrence of an intramolecular electron transfer from the carboxyl group to the oxidized sulfur function followed by homolytic carbon-carboxyl bond breakage into carbon dioxide and the [alpha]-(alkylthio)alkyl radical. The OH radical-induced decarboxylation can receive part of its driving force from the resonance stabilization of the R-S-CH[sub 2][center dot] radical resulting from CO[sub 2] cleavage. 41 refs., 3 figs., 2 tabs.

• OSTI ID: 5115222
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 97:51; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400102 -- Chemical & Spectral Procedures
400201* -- Chemical & Physicochemical Properties
400600 -- Radiation Chemistry
ABSORPTION SPECTRA
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CARBOXYLIC ACIDS
CHALCOGENIDES
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHROMATOGRAPHY
DATA
DECARBOXYLATION
DECOMPOSITION
ELECTRON TRANSFER
EXPERIMENTAL DATA
HEAVY WATER
HYDROGEN COMPOUNDS
HYDROXYL RADICALS
INFORMATION
KINETICS
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PH VALUE
RADIATION EFFECTS
RADICALS
RADIOLYSIS
REACTION KINETICS
SEPARATION PROCESSES
SPECTRA
WATER