- Photocatalytic degradation of dyes by AgBr/Ag3PO4 and the ecotoxicities of their degraded products
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Ag3PO4 powders were prepared through a precipitation reaction between AgNO3 and precipitating agent solutions that were prepared by adjusting the amount of H3PO4 in the Na3PO4 solutions. The Ag3PO4 powders prepared from the precipitation solution with a pH of 6 showed the highest photocatalytic activity for decolorizing the methylene blue and rhodamine B dyes. These Ag3PO4 powders were further modified by the addition of KBr solutions to obtain AgBr/Ag3PO4 powders and these photocatalysts can decolorize the anionic dyes as reactive orange and methyl orange. The reactive species involved in the photocatalytic degradation process were evaluated for their inhibitory activity using the appropriate scavengers. After photocatalysis, mass spectrometry confirmed that the dyes were degraded to smaller molecules. The ecotoxicities of the dye solutions before and after treatment were evaluated by studying their ability to inhibit the growth of the bioindicator Chlorella vulgaris.
- Amornpitoksuk, Pongsaton,Suwanboon, Sumetha
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p. 711 - 719
(2016/05/19)
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- Photochemical cleavage reactions of 8-quinolinyl sulfonates in aqueous solution
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Photochemical cleavage reactions of 8-quinolinyl benzenesulfonate derivatives and related sulfonates in aqueous solutions are reported. The 8-quinolinyl benzenesulfonates undergo photolysis upon photoirradiation at 300-330 nm to give the corresponding 8-quinolinols and benzenesulfonic acids with the production of only negligible amounts of byproducts. The effects of substituent groups of the 8-quinolinyl moiety and the benzene ring on the photolysis reactions were examined. Based on steady-state mechanistic studies using a triplet sensitizer, a triplet quencher, and electron donors, it was suggested that the photolysis proceeds mainly via the homolytic cleavage of S-O bonds in the excited triplet state.
- Kageyama, Yoshiyuki,Ohshima, Ryosuke,Sakurama, Kazusa,Fujiwara, Yoshihisa,Tanimoto, Yoshifumi,Yamada, Yasuyuki,Aoki, Shin
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experimental part
p. 1257 - 1266
(2010/05/02)
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- Regioselectivity and the nature of the reaction mechanism in nucleophilic substitution reactions of 2,4-dinitrophenyl X-substituted benzenesulfonates with primary amines
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Second-order rate constants have been measured for the reaction of 2,4-dinitrophenyl X-substituted benzenesulfonates with a series of primary amines. The nucleophilic substitution reaction proceeds through competitive S-O and C-O bond fission pathways. The S-O bond fission occurs dominantly for reactions with highly basic amines or with substrates having a strong electron-withdrawing group in the sulfonyl moiety. On the other hand, the C-O bond fission occurs considerably for the reactions with low basic amines or with substrates having a strong electron-donating group in the sulfonyl moiety, emphasizing that the regioselectivity is governed by both the amine basicity and the electronic effect of the sulfonyl substituent X. The apparent second-order rate constants for the S-O bond fission have resulted in a nonlinear Bronsted-type plot for the reaction of 2,4-dinitrophenyl benzenesulfonate with 10 different primary amines, suggesting that a change in the rate-determining step occurs upon changing the amine basicity. The microscopic rate constants (k1 and k2/k-1 ratio) associated with the S-O bond fission pathway support the proposed mechanism. The second-order rate constants for the S-O bond fission result in good linear Yukawa-Tsuno plots for the aminolyses of 2,4-dinitrophenyl X-substituted benzenesulfonates. However, the second-order rate constants for the C-O bond fission show no correlation with the electronic nature of the sulfonyl substituent X, indicating that the C-O bond fission proceeds through an SNAR mechanism in which the leaving group departure occurs rapidly after the rate-determining step.
- Um, Ik-Hwan,Hong, Jin-Young,Kim, Jung-Joo,Chae, Ok-Mi,Bae, Sun-Kun
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p. 5180 - 5185
(2007/10/03)
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- The Hammett equation applied to the nucleophilic displacement of ions and ion pairs on substituted benzenesulphonates
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Nucleophilic substitution on meta- and para-substituted methyl benzenesulphonates was studied with two chloride salts with different structures: NBu4Cl or KCl-Kryptofix 2,2,2. Treating the results with the Acree equation shows that the reaction proceeds by two reaction paths, one involving the chloride ion and the other, slower one, involving the ion pairs. Treating the results with the Hammett equation gives consistent data, and shows that ρ is positive and nearly the same for the two reaction paths (ρ ≈ +2). The reactivity of methyl p-nitrobenzenesulphonate was compared with that of the corresponding ethyl derivative, and it is shown that the methyl derivative reacts faster than the ethyl derivative in both paths. The results are interpreted based on the assumption that in both paths a negative charge is developed on the leaving group in the transition state, and that the activated complex is linear. Copyright
- Alunni, Sergio,Pica, Monica,Reichenbach, Gustavo
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p. 265 - 270
(2007/10/03)
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- The Hammett equation and micellar effects on SN2 reactions of methyl benzenesulfonates - The role of micellar polarity
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Substituent effects on the reaction of H2O, OH-, and Br- with p-substituted methyl benzenesulfonates in cationic micelles of cetyl trialkylammonium ion surfactants (n-C16H33NR3X, X = OH, Br, R = Me, Et, nPr, nBu) and in water were analyzed by using the Hammett equation. Values of p in the various media confirm that micellar interfacial regions are less polar than water and polarities decrease with increasing bulk of the surfactant head-group. Wiley-VCH Verlag GmbH, 2000.
- Brinchi, Lucia,Di Profio, Pietro,Germani, Raimondo,Savelli, Gianfranco,Spreti, Nicoletta,Bunton, Clifford A.
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p. 3849 - 3854
(2007/10/03)
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- Micellar Effects upon Substitutions by Nucleophilic Anions
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Micellar effects upon of OH- with p-nitrophenyl diphenyl phosphate or 2,4-dinitro-1-chloronaphthalene have been examined with cetyltrimethylammonium surfactants, (CTAX, X=Cl, Br, (SO4)1/2).Demethylations of methyl benzene- or naphthalene-2-sulfonate by halide ion have been examined. in micelles of CTACl, CTABr, CTA(SO4)1/2, or cetyltrimethylammonium mesylate (CTAOMs) and for demethylation by OH- or SO32- in CTA(SO4)1/2 or CTAOMs.The rate enhancements have been treated in terms of concentrations of the substrates and the nucleophilic anion at the micellar surface.The anion concentrations depended upon nonspecific Coulombic and specific interactions that were calculated by solving the Poisson-Boltzmann equation.The same structural parameters were used in fitting data for reactions with Cl- or Br- as nucleophiles and for systems with Cl- or Br- as inert anions that were competing with OH- or SO32-.The treatment is applicable to mixtures of database to mixtures of dilute mono- and dianions.
- Bunton, Clifford A.,Moffat, John R.
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p. 2896 - 2902
(2007/10/02)
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- Hydrophobic and steric effects on the ion-pair formation of tris(1,10-phenanthroline)iron(II) and arenesulfonate ions. Kinetic determination of the formation constants of the ion pairs and a 1H NMR study of their structures
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Ion-pair formation constants (K) for Fe(phen)32+ and six kinds of arenesulfonate ions were obtained from kinetic studies of the aquation of the complex ion in aqueous sodium arenesulfonate solutions: K = 5 ± 1, 13 ± 2, 28 ± 5, 19 ± 3, 8 ± 2, and 5 ± 1 mol-1 dm3 for benzene-, 4-methylbenzene-, 4-ethylbenzene-, 2,4-dimethylbenzene-, 1-naphthalene-, and 2-naphthalenesulfonate, respectively. An arenesulfonate of greater hydrophobicity showed a larger formation constant, except that small formation constants were shown by bulky naphthalenesulfonates. The formation constant was smaller for an arenesulfonate than for an alkanesulfonate with the same number of carbon atoms. The 1H NMR signal of arenesulfonate in the ion pair was found to shift upfield. Comparison of the observed shifts with those calculated on the basis of the current loop model supported a model of the ion pair in which the arenesulfonate ion lies in the hydrophobic cavity between two phenanthroline ligands of the complex ion with the sulfonate group directed outside the cavity.
- Tachiyashiki, Satoshi,Yamatera, Hideo
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p. 3209 - 3211
(2008/10/08)
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- Micellar Effects upon Spontaneous and Carboxylate Ion Catalyzed Hydrolyses of Benzenesulfonyl Chlorides
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Spontaneous hydrolyses of benzenesulfonyl chlorides are inhibited by micelles of cetyltrimethylammonium chloride (CTACl), sodium dodecyl sulfate (SDS), and N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (SB3-16).The rate constants for hydrolyses of fully bound substrates are similar in CTACl and SB3-16.The rate constants in CTACl (k+) and SDS (k-) depend on the electronic effects of the 4-substituents and k+/k- increases in the sequence MeO Me H Br NO2.These micellar charge effects are ascribed to changes in the extents of bond-making and -breaking in the transition state.Hydrolysis in micellized N-dodecyl-N,N-dimethylglycine (B1-12) is inhibited, but this effect is offset by nucleophilic participation by the carboxylate moiety.Electron-withdrawing substituents strongly favor nucleophilic participation and for the 4-bromo and 4-nitro derivatives second-order rate constants in zwittwerionic betaine micelles of B1-12 are similar to those for reaction with nonmicellized N,N,N-trimethylglycine in water.
- Bunton, Clifford A.,Mhala, Marutirao M.,Moffatt, John R.
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p. 4921 - 4924
(2007/10/02)
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- Intramolecular Reactions. Part 12. Ring Size and Leaving Group Effects on Inter- and Intra-molecular Nucleophilic Substitution by Carbanions
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In cyclisations of aryl ο-halogenoalkyl ketones to aryl cycloalkyl ketones with base, cyclopropanes are formed up to 23000 times faster than cyclopentanes.Hydrogen-deuterium exchange experiments and very low bromide-chloride ratios (1.9) for three-membered ring formation are consistent with rate-determining deprotonation of the ketone.By contrast, in five-membered ring formation, hydrogen-deuterium exchange adjacent to the carbonyl group occurs much faster than cyclisation and the chloride-bromide ratio is 'normal' at 99.In formation of arylsulphonylcyclopropanes from arylsulphonylpropyl arenesulphonates, the Hammett ρ value for the leaving group is +1.7, and for intermolecular substitution by bis-sulphonyl stabilised carbanions, +1.2.Attempts to obtain ρLG values for five-membered ring formation were frustrated by competing intermolecular reactions.The results are discussed against the background of previous work on ring formation by intramolecular nucleophilic substitution.
- Bird, Roger,Griffiths, Gwerydd,Griffiths, Gwynfor F.,Stirling, Charles J. M.
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p. 579 - 584
(2007/10/02)
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- Nucleophilic Substitution at Sulphur. Part 3. The Alkaline Hydrolysis of Some Cyclic and Open-chain Sulphonate Esters
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The rates of alkaline hydrolysis of a number of aryl cyclic and open-chain sulphonate esters have been studied at various temperatures.The enthalpies and entropies of activation have been determined.The difference in reactivity between the five-membered sultone and other cyclic and open-chain analogues is shown to arise from a combination of both enthalpy and entropy strain.The detailed mechanism of alkaline hydrolysis of sulphonate esters and the cause of ring strain in sultones are discussed in some detail.
- Laleh, Ahmed,Ranson, Richard,Tillett, John G.
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p. 610 - 615
(2007/10/02)
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