3117-05-3Relevant academic research and scientific papers
Kinetics of oxidation of hydroquinones by molecular oxygen. Effect of superoxide dismutase
Roginsky, Vitaly,Barsukova, Tatyana
, p. 1575 - 1582 (2007/10/03)
The kinetics of the autoxidation of sixteen hydroquinones (QH2) (substituted 1,4-hydroquinones and 1,4-dihydroxynaphthalenes as well as 9,10-dihydroxyphenanthrene) were studied using the Clark electrode technique in aqueous solution, pH 7.40, at 37°C both with and without added superoxide dismutase (SOD). QH2 oxidation occurs typically with a self-acceleration. A maximum rate of oxidation, RMAX, was found to be the most indicative parameter characterizing QH2 oxidizability. A kinetic scheme of QH2 autoxidation was developed; computer simulations carried out on the basis of this scheme reproduce the main kinetic features of the studied process. QH2 autoxidation is suggested to be a free-radical chain process with semiquinone (Q-) and superoxide (O2-) as chain-carrying species. The oxidation is initiated by reaction (1) Q + QH2→2Q- + 2H+. The addition of SOD results in two main effects: shifting the equilibrium (2) Q- + O2?Q + O2- (K2) to the right and suppressing reaction (3) QH2 + O2-→Q- + H2O2. The net effect of SOD depends basically on K2. When K2 2 > 0.1, the more SOD inhibits the oxidation, the higher K2. The concentration of SOD causing the 50%-effect on RMAX ([SOD]50), both inhibitory and stimulatory, decreases dramatically when K2 increases. At [SOD] ? [SOD]50 the rate of QH2 autoxidation is definitively determined by the rate of reaction (1). For the majority of QH2, [SOD]50 is significantly less than the physiological values of [SOD] and thus QH2 autoxidation in biological environment is expected to occur in the above kinetically simple mode.
Comparative pulse radiolysis studies of alkyl- and methoxy-substituted semiquinones formed from quinones and hydroquinones
Roginsky, Vitaly A.,Pisarenko, Leonid M.,Bors, Wolf,Michel, Christa,Saran, Manfred
, p. 1835 - 1840 (2007/10/03)
Absorption spectra and rate constants for the disproportionate of 12 alkyl- and methoxy-substituted semiquinone anion free radicals (Q?-) produced by the one-electron reduction (using CO2?- as a reductant) of 1,4-benzoquinones and 1,4-naphthoquinone (Q) as well the oxidation (using N3? as an oxidant) of the corresponding hydroquinones (QH2) were determined by pulse radiolysis in 50 mM sodium phosphate buffer, pH 7.40 at room temperature. Both spectral and kinetic characteristics of Q?- only moderately depended on whether Q?- was produced from Q or QH2. Spectra of benzosemiquinones display two peaks with maximum at 310-320 nm and ca. 430 nm with the ratio of about 2-2.5. Molar absorption coefficients were determined. Rate constants for Q?- disproportionation (2k1) were correlated with the nature of substituents. While 2k1 was scarcely affected by methyl substitution, Q?- containing isopropyl, tert-butyl and methoxy substituents were visibly more stable than non-substituted and methyl-substituted Q?-.
Reactive dyestuffs
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, (2008/06/13)
Triphendioxazine reactive dyestuffs of the general formula STR1 with the substituent definition given in the description, are outstandingly suitable for dyeing and printing materials containing hydroxyl groups or amide groups. They give red dyeings with high wet- and light-fastnesses.
Triphendioxazine dyestuffs
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, (2008/06/13)
Triphendioxazine dyestuffs of the formula STR1 having the substituent meanings specified in the descriptive part, are highly suitable for dyeing and printing hydroxyl- or amido-containing materials, in particular fibre materials, and produce wash-fast dyeings and prints.
An Improved Synthesis of 1,4-Benzo- and 1,4-Naphthoquinones Bearing Active Substituents
Syper, Ludwik,Kloc, Krystian,Mlochowski, Jacek
, p. 808 - 822 (2007/10/02)
The synthesis of 1,4-benzoquinones and 1,4-naphthoquinones 3a-j carrying substituents such as methoxyl, allyl or oxiranyl was substantially improved.The 1-methoxy-4-methoxymethyloxy 2a-d, g-k or 1,4-bis(methoxymethyloxy) derivatives 2e-f were used, as a substrates instead of 1,4-dimethoxy derivatives 1a-j hitherto used and they were oxidized with silver(II) dipicolinate.Among numerous examples, the synthesis of a new analog of ubiquinone 3d with the oxiranyl substituent, being a new bioactivated alkylating agent, is reported.
