Oxidation of 10-methylacridan, a synthetic analogue of NADH, and deprotonation of its cation radical. Convergent application of laser flash photolysis and direct and redox catalyzed electrochemistry to the kinetics of deprotonation of the cation radical

Journal Article · Wed Mar 20 23:00:00 EST 1991 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100159a047· OSTI ID:5757041

Anne, A; Moiroux, J; Saveant, J M ^[1]; Hapiot, P; Neta, P ^[2]

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1. Univ. of Paris-7 (France)
2. National Inst. of Standards and Tech., Gaithersburg, MD (United States)

Photolysis of 10-methylacridan (AH) in acetonitrile solutions containing CCl{sub 4} led to quantitative oxidation of AH to A{sup +}. Laser flash photolysis of the solution with 248- or 308-nm light yielded the cation radical AH{sup {sm bullet}+} which decays by deprotonation to give the neutral radical A{sup {sm bullet}}. AH{sup {sm bullet}+} could be also generated by means of homogeneous redox catalysis using variously substituted ferrocenes and the rate of deprotonation k{sub H} by various bases was derived from both techniques. There is a good agreement between the values determined for k{sub H} (here and, previously, by direct electrochemistry using ultramicroelectrodes). The vast majority of the data points in a plot of log k{sub H} vs the pK{sub a} of the bases, covering 18 pK{sub a} units and rate constants up to the diffusion limit, fall on the same Broensted line in spite of the fact that they involve bases of quite different structure pyridines, aliphatic nitrogen bases, and carboxylates. {gamma}-Radiolysis of acetonitrile/CCl{sub 4}/AH solutions also resulted in quantitative oxidation to A{sup +}. However, pulse radiolysis of this system indicated relatively slow oxidation of AH by Cl{sub 3}COO{sup {sm bullet}} radicals. Pulse radiolysis experiments in acidic aqueous solutions showed that AH is oxidized by Cl{sub 2}{sup {sm bullet}{minus}} to give AH{sup {sm bullet}+}, which decays with a first-order rate constant of 9 {times} 10{sup 2} s{sup {minus}1}. Reduction of A{sup +} gave A{sup {sm bullet}} which did not undergo protonation even at 2 M HClO{sub 4}, but reaction of A{sup +} with H atoms resulted in partial addition of H to the 9-position to give AH{sup {sm bullet}+}.

• OSTI ID: 5757041
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 95:6; ISSN 0022-3654; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
400400 -- Electrochemistry
400500 -- Photochemistry
ABSORPTION SPECTROSCOPY
ALKYLATED AROMATICS
AQUEOUS SOLUTIONS
AROMATICS
AZINES
BASES
BIOLOGICAL MODELS
CATALYSIS
CATIONS
CHARGED PARTICLES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISTRY
COMPLEXES
DECOMPOSITION
DIENES
DISPERSIONS
ELECTROCHEMISTRY
ELECTROMAGNETIC RADIATION
FERROCENE
HETEROCYCLIC COMPOUNDS
HOMOGENEOUS CATALYSIS
HYDROCARBONS
IONS
IRON COMPLEXES
KINETICS
LASER RADIATION
MATHEMATICAL MODELS
MIXTURES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
OXIDATION
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
POLYENES
PYRIDINES
RADIATIONS
RADICALS
REACTION KINETICS
SOLUTIONS
SPECTRA
SPECTROSCOPY
THERMODYNAMICS
TRANSITION ELEMENT COMPLEXES
VISIBLE SPECTRA
VOLTAMETRY