16722-51-3Relevant articles and documents
Cationic mixed micelles as reaction medium for hydrolysis reactions
Fernández, Isabel,Pérez-Juste, Jorge,Hervés, Pablo
, p. 1866 - 1874 (2015)
The influence of cationic mixed micelles composed of quartenary ammonium surfactants on hydrolysis reactions has been studied in detail. The basic hydrolysis of N-methyl-N-nitroso-p-toluene sulphonamide has been chosen as the reaction probe, while mixed micelles composed of lauryl trimethyl ammonium chloride and octadecyl trimethyl ammonium chloride with different molar ratios were studied as the reaction medium. The ion-exchange pseudophase model was used to fit the experimental results to obtain the kinetic and thermodynamic parameters of the reaction. The result show that the hydrophobic character of the mixed micelles drives the association of the substrate to them, leading to a local increase of reactant concentrations at the micellar interface and, therefore, to a catalytic effect. By tuning the molar ratio of the mixed micelles it is possible to control substrate binding affinity and thus the catalytic efficiency of the reaction medium.
Micellar Effects upon Spontaneous and Carboxylate Ion Catalyzed Hydrolyses of Benzenesulfonyl Chlorides
Bunton, Clifford A.,Mhala, Marutirao M.,Moffatt, John R.
, p. 4921 - 4924 (1985)
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.
Regioselectivity and the nature of the reaction mechanism in nucleophilic substitution reactions of 2,4-dinitrophenyl X-substituted benzenesulfonates with primary amines
Um, Ik-Hwan,Hong, Jin-Young,Kim, Jung-Joo,Chae, Ok-Mi,Bae, Sun-Kun
, p. 5180 - 5185 (2007/10/03)
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.
The Hammett equation applied to the nucleophilic displacement of ions and ion pairs on substituted benzenesulphonates
Alunni, Sergio,Pica, Monica,Reichenbach, Gustavo
, p. 265 - 270 (2007/10/03)
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
The Hammett equation and micellar effects on SN2 reactions of methyl benzenesulfonates - The role of micellar polarity
Brinchi, Lucia,Di Profio, Pietro,Germani, Raimondo,Savelli, Gianfranco,Spreti, Nicoletta,Bunton, Clifford A.
, p. 3849 - 3854 (2007/10/03)
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.
Decomposition of N-Methyl-N-nitrosotoluene-p-sulphonamide in Basic Media: Hydrolysis and Transnitrosation Reactions
Castro, Albino,Leis, J. Ramon,Pena, M. Elena
, p. 1861 - 1866 (2007/10/02)
The decomposition of N-methyl-N-nitrosotoluene-p-sulphonamide (MNTS) has been studied in basic and neutral water-alcohol mixtures.In alkaline media and when OH- was the nucleophile, the known hydrolysis reaction in which OH- attacks the SO2 group was observed; this reaction was first order in both OH- and MNTS.In the presence of ammonia, hydroxylamine, hydrazine, or primary, secondary or tertiary amines, a transnitrosation reaction took place in which the addditional nucleophiles attacked the nitrogen atom of the MNTS N=O group; this reaction was first order in both MNTS and free amine.In particular, MNTS proved to be as efficient as some alkyl nitrites for the nitrosation of secondary amines in neutral or alkaline media, in which conventional nitrosating agents do not exist.Similar reaction rates were observed for the more basic tertiary amines (which gave NO2- among the final products).Primary amines underwent rather slower reactions, with the exception of hydroxylamine and hydrazine, the nucleophilic nature of which is increased by the α effect.We discuss the relative reactivities of the various amines in terms of their basicity and vertical ionization potentials, and we report the effect of the proportion of alcohol in the medium on the rates of both hydrolysis and transnitrosation reactions.
Group Transfers III. Consequences of the Application of the Marcus Equation
Lewis, Edward S.
, p. 259 - 262 (2007/10/02)
The rates of many group transfers are well described by the Marcus equation.Alkyl transfers in the solvent sulfolane, the formal transfers of R+ from one nucleophile to another, fit almost within experimental error.In these fairly slow reactions the Marcus quadratic term is negligible.Neglect of this term leads to absence of Reactivity Selectivity principle correlations.It leads to a scale of nucleophilicities and one of methylating power.In contrast, many nonalkyl transfers have much lower intrinsic barriers, and neglect of the quadratic term is unjustifiable.For alkyl transfers there is no general correlation between rate and equilibrium constants.When closely related series, such as a Hammett variation in the leaving group or nucleophile are studied, there is generally a rate-equilibrium LFER.From the slope of this rate-equilibrium LFER, the charge, δ, on the transferring group is calculated.The variation in this charge, which is structurally plausible, gives a new perspective on the rates of SN2 reactions, including benzylic, and α-halocarbonyl systems.
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
Tachiyashiki, Satoshi,Yamatera, Hideo
, p. 3209 - 3211 (2008/10/08)
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.
Reaction of Arenesulphonyl Halides with Free Radicals. Part 2
Correa, Carlos M. M. da Silva,Oliveira, Maria Augusta B. C. S.
, p. 711 - 716 (2007/10/02)
The generation of arenesulphonyl radicals by halogen abstraction from arenesulphonyl bromides and iodides is described.The relative reactivities of halogen abstraction by phenyl, 1-cyano-1-methylethyl, and benzyl radicals in benzene solution at 60 deg C are reported.These relative reactivities are almost independent of the nature of the substituents on the benzene ring of ArSO2Br.Sulphonyl iodides are more reactive towards phenyl radicals than bromides which in turn are more reactive than the corresponding chlorides (relative reactivities 602:192:1).
