4-Carboxybenzophenone-sensitized photooxidation of sulfur-containing amino acids in alkaline aqueous solutions. Secondary photoreactions kinetics

Journal Article · Thu Jan 13 04:00:00 EST 1994 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100053a031· OSTI ID:5154275

Bobrowski, K; Hug, G L ^[1]; Marciniak, B ^[2]; Kozubek, H ^[3]

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1. Univ. of Notre Dame, IN (United States)
2. Univ. of Notre Dame, IN (United States) A. Mickiewicz Univ., Poznan (Poland)
3. A. Mickiewicz Univ., Poznan (Poland)

Sulfur-containing amino acids and alanine were oxidized via photosensitization by 4-carboxybenzophenone (CB) in alkaline aqueous solutions. The mechanism of this reaction was examined using steady-state and laser flash photolysis techniques. The rate constants were determined for the quenching of the CB triplet state by five sulfur-containing amino acids and alanine and were found to be approximately 10[sup 9] and 1.8 x 10[sup 8] M[sup [minus]1] s[sup [minus]1], respectively. The observation of the (S therefore S)[sup +] radical cations of some of the amino acids showed that the quenching process involves an electron transfer from the sulfur atom to the triplet state of CB. A show process of formation of the ketyl radical anion occurring on the microsecond time scale was assigned to the one-electron reduction of CB by the [alpha]-aminoalkyl radicals that were formed earlier as a result of an intramolecular electron transfer from the carboxyl group to the sulfur-centered radical cation followed by decarboxylation. For thiaproline, the pseudo-first-order rate constant, k[prime][sub obs], which characterizes the slow process of secondary ketyl radical anion formation, is linearly dependent on the CB concentration over the pH region 9.4-13.4. A detailed mechanism for the primary and the secondary photoreduction of CB is proposed and discussed. 32 refs., 7 figs., 5 tabs.

• OSTI ID: 5154275
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 98:2; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
400500 -- Photochemistry
ALANINES
ALKALI METAL COMPOUNDS
AMINO ACIDS
ANIONS
AQUEOUS SOLUTIONS
BENZOPHENONE
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CARBOXYLIC ACIDS
CATIONS
CHALCOGENIDES
CHARGED PARTICLES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COMPILED DATA
DATA
DECARBOXYLATION
DECOMPOSITION
DISPERSIONS
DRUGS
EFFICIENCY
ELECTROMAGNETIC RADIATION
ELECTRON TRANSFER
EQUILIBRIUM
INFORMATION
IONS
KETONES
KINETICS
LASER RADIATION
LIPOTROPIC FACTORS
METHIONINE
MIXTURES
MULTIPLETS
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PH VALUE
PHOTOCHEMICAL OXIDANTS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
PHOTOSENSITIVITY
QUANTUM EFFICIENCY
QUENCHING
RADIATIONS
RADICALS
REACTION KINETICS
REDUCTION
SENSITIVITY
SOLUTIONS
SULFUR COMPOUNDS
TRIPLETS