- Textile dye degradation potential of plant laccase significantly enhances upon augmentation with redox mediators
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Cell suspension cultures of Blumea malcolmii Hook. exhibited 98% decolorization of a textile dye Brilliant Blue R (BBR) at a concentration of 40 mg L-1 within 24 h. A significant induction in the intracellular laccase activity (607%) was observ
- Kagalkar, Anuradha N.,Khandare, Rahul V.,Govindwar, Sanjay P.
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- Phenylthio-derivatives of α-methylene-γ-lactones as pro-drugs of cytotoxic agents
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A series of substituted phenylthio-derivatives of grosheimin (1), a natural cytotoxic guaianolide, were investigated with the aim of providing insight into their mechanism of action as cytotoxic agents against KB cell lines. Hydrolysis data, kinetics, in the presence and in the absence of H2O2, and the valuation of lipophilicity were correlated with cytotoxicity values and with Hammett-σ-values of substituents (R) at the thiophenol ring. These compounds behave as 'pro-drugs' which release the cytotoxic agent grosheimin by sulphur-oxidation promoted by H2O2 and subsequent retro- elimination which depends on the nature and position of the R substituent.
- Fardella, Giuseppe,Barbetti, Paolo,Grandolini, Giuliano,Chiappini, Ione,Ambrogi, Valeria,Scarcia, Vito,Furlani Candiani, Ariella
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p. 515 - 523
(2007/10/03)
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- Tetrakis(pyridine)silver(II) Peroxodisulfate, S2O8, a Reagent for the Oxidative Transformations
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Tetrakis(pyridine)silver(II) peroxodisulfate oxidizes aromatic aldehydes to carboxylic acids, benzylic alcohols to carbonyl compounds, aromatic thiols, and allylaryl thioethers to arylsulfonic acids and benzylic carbon-hydrogen bonds to carbonyl groups. α-Hydroxycarboxylic acids and phenylacetic acids are decarboxylated to produce carbonyl compounds.Dibenzyl ether and its sulfur analogue are converted to their corresponding ester and the thioester, respectively.
- Firouzabadi, Habib,Salehi, Peyman,Mohammadpour-Baltork, Iraj
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p. 2878 - 2880
(2007/10/02)
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- Acid-catalyzed hydrolysis of benzenesulfonamides. Rate enhancements by ortho-alkyl substituents
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Pseudo-first-order rate constants have been measured for the acid-catalyzed hydrolysis of a series of N,N-dimethyl- and N-methyl-N-phenylbenzenesulfonamides in 70 percent (v/v) CF3CO2H/H2O at 99 deg C.Analysis of the effect of the alkyl substituents in the benzene ring shows a remarkable rate enhancement by ortho-alkyl groups, in the contrast with a rate retardation of similar substituents in the corresponding benzamides.The rate enhancement in the sulfonamides is attributed to relief of initalstate strain in the transition state for hydrolysis.When the sulfonamide moiety is contained in a five-membered ring fused to a phenyl ring, the rate of hydrolysis is markedly reduced by an ortho-methyl substituent.
- Wagenaar, Anno,Kirby, Anthony J.,Engberts, Jan B. F. N.
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p. 203 - 205
(2007/10/02)
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- SULFONATION DU BENZENE ET DU TOLUENE PAR LE TRIOXYDE DE SOUFRE. PROPOSITION D'UN MECANISME
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Benzene and Toluene sulfonation kinetics have been studied in two solvents (CH3Cl and CCl4).Mechanisms are given to represent competitive kinetics between the two hydrocarbons and isomer distribution of toluene sulfonic acids.Only chain mechanism using pyrosulfonic acid seems to fit the experimental data.
- Homsi, A. el,Guiglion, C.,Guiraud, R.
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p. 383 - 390
(2007/10/02)
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- EFFECT OF STRUCTURE ON THE KINETICS AND MECHANISM OF THE ACID-CATALYZED DECOMPOSITION OF N-ALKYL-N-NITROBENZENESULFONAMIDES
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The decomposition rate of a series of meta- and para-substituted N-alkyl-N-nitrobenzenesufonamides was determined by a spectrophotometric method in aqueous sulfuric acid.It was shown that the decomposition of the compounds takes place both by denitration and by cleavage of the N-S bond with the formation fo primary aliphatic N-nitrosamines.Electron-withdrawing substituents in the aromatic ring shift the process toward denitration.
- Drozdova, O. A.,Astrat'ev, A. A.,Kuznetsov, L. L.,Selivanov, V. F.
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p. 671 - 675
(2007/10/02)
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- HYDROLYSIS OF AROMATIC SULFONIC ACIDS UNDER THERMODYNAMIC CONTROL OF THE REACTION
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Linear mathematical models which describe the hydrolysis of alkyl- and halobenzenesulfonyl acids under the conditions for their isomerization in sulfuric acid have been obtained by the method of mathematical experiment planning.The value of the effective rate constants of hydrolysis calculated according to the models for comparative conditions (150 deg C, 3 moles of 85percent sulfuric acid) were used to obtain the correlation between log kh and the ? constants of the substituents.The correlation corresponds the electrophilic nature of the hydrolysis process (ρ = -4.69).The strong influence of the electronic effects of the substituents on the rate of hydrolysis is an indication of the development of a considerable positive charge on the reaction center in the transition state.
- Krylov, E. N.,Volgina, L. V.,Isaeva, G. Yu.
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p. 1129 - 1133
(2007/10/02)
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- EFFECT OF STRUCTURE ON THE KINETICS AND MECHANISM OF THE ACID-CATALYZED DECOMPOSITION OF N-NITROBENZENESULFONAMIDES
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The decomposition rate of a series of ring-substituted N-nitrobenzenesulfonamides in aqueous sulfuric acid was measure by a spectrophotometric method.Decomposition of the compounds takes place both by the cleavage of the N-S bond to form the corresponding sulfonic acid, nitrous oxide, and water and by denitration.In crease in the electronegativity of the substituent in the aromatic ring promotes the denitration reaction.
- Drozdova, O. A.,Astrat'ev, A. A.,Kuznetsov, L. L.,Selivanov, V. F.
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p. 2063 - 2067
(2007/10/02)
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- ISOMERIZATION OF TOLUENESULFONIC ACIDS IN THE PRESENCE OF SULFURIC ACID
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The isomerization of p- and o- toluenesulfonic acids was investigated in relation to the temperature (160 - 200 deg C), concentration (66 - 92 percent), and amount of sulfuric acid (1-5 moles per mole of sulfonic acid).It was shown that the formation rate of the meta isomer from the ortho and para isomers is described by a pseudofirst-order equation for irreversible processes.The isomerization rate depends on the amount of sulfuric acid, which plays the role of active medium.The transformation of the ortho and para isomers to meta-toluenesulfonic acid takes place fairly quickly in a medium with a sulfuric acid content (70 - 85percent) of up to 2 -3 moles per mole of sulfonic acid at 180 - 200 deg C.This makes it possible to obtain a mixture of toluenesulfonic acids with a predominating content of the meta isomer after times in the order of 2 - 3 h.
- Kozlov, V. A.,Popkova, I. A.
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p. 764 - 768
(2007/10/02)
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