Kalyan K. Banerji

Mechanism of the oxidation of organic sulphides by permanganate ion

Abstract The kinetics of the oxidation of number of aryl methyl, alkyl phenyl, dialkyl and diphenyl sulphides by permanganate ion to yield the sulphoxides, have been studied. The reaction is first order with respect to the sulphide and permanganate and is independent of hydrogen ion concentration. The reaction exhibited negative polar reaction constants and a small degree of steric hindrance. The lack of solvent isotope effect and the observed solvent effect ( m = 0.39 for McSPh) are explained by an electrophilic attack of permanganate-oxygen on the sulphide yielding a polar transition state. A moderate anchimeric assistance was observed in the oxidation of o -C00Me and o -C00H substituted methyl phenyl sulphide. A mechanism involving a one-step electrophilic oxygen transfer from permanganate ion to the sulphide and a polar product-like transition state, has been proposed.

An Unprecedented-Type Intramolecular Redox Reaction of Solid Tetraamminecopper(2) Bis(permanganate) ((Cu(NH3)4)(MnO4)2 )±A Low-Temperature Synthesis of Copper Dimanganese Tetraoxide-Type (CuMn2O4) Nanocrystalline Catalyst Precursors

b ), Istva ¬ n Sajo ¬ a ), Ja ¬ nos Kristo ¬f c Tetraamminecopper(2) bis(permanganate) ((Cu(NH3)4)(MnO4)2; 1) was prepared, and its properties were studied in both aqueous solution and the solid phase. The presence of H-bond interactions between the ammonia ligand of the complex cation and an O-atom of the permanganate ion was detected by IR and Raman methods. The solid-phase thermal deammoniation of 1 led to an unusual intramolecular redox reaction between the MnO¥¥¥H N linkage with formation of NH4NO3 and CuMn2O4-type mixed oxides instead of stepwise deammoniation, even below 100. The thermal deammoniation of 1 in aqueous solution led, instead of to hydrated copper(2) bis(permanganate), to the formation of NH4MnO4 (2). Since the temperature of the thermal deammoniation of 1 is lower than the decomposition temperature of the permanganate ion, the regulated solid-phase decomposition of 1 allowed preparation of CuMn2O4-type oxides with mixing of copper and manganese at the atomic level.

Kinetics and mechanism of the oxidation of substituted benzyl alcohols by [bis(trifluoroacetoxy)iodo]benzene

The oxidation of substituted benzyl alcohols by bis(trifluoroacetoxy)iodo]benzene in aqueous acetic acid solution results in the formation of the corresponding benzaldehydes. The reaction is first order with respect to each of the alcohol, TFAIB and hydrogen ions. The oxidation of [1,1-2H2]benzyl alcohol exhibited the presence of a substantial primary kinetic isotope effect, indicating the cleavage of the α-C–H bond in the rate-determining step. Increase in the amount of water, in the solvent mixture of acetic acid and water, results in a decrease of the reaction rate. The analysis of the substituent effect in terms of Chartons LDR equation yielded an excellent correlation with negative reaction constants. A mechanism involving a hydride-ion transfer in the rate-determining step has been proposed.

Three Reagents in One: Ammonium Permanganate in the Oxidation of Benzyl Alcohol

The oxidation or consecutive ammoxidation reaction of benzyl alcohol with solid ammonium permanganate was studied. The first oxidation step leads to the formation of benzaldehyde, ammonia, and MnO2. The MnO2 is present in the system in a colloidal form which facilitates the reaction between aldehyde and ammonia, and this latter reaction then yields benzonitrile. All these products are formed in a heterogeneous system under relatively mild conditions. The yield of benzaldehyde has an optimum at room temperature and increases with increasing reaction time. At higher temperature (e.g. 80 °C) benzonitrile is formed together with minor amounts of benzyl benzoate

Kinetics and mechanism of the oxidation of aliphatic aldehydes by hexamethylenetetramine-bromine

Oxidation of aliphatic aldehydes by hexamethylenetetramine-bromine proceeds by a mechanism involving transfer of a hydride ion from the aldehyde to the oxidantvia an intermediate complex.

Kinetics and mechanism of the oxidation of substituted benzyl alcohols by sodium N-bromobenzenesulfonamide

The oxidation of substituted benzyl alcohols by sodium N-bromobenzenesulfonamide (BAB) in acid solution results in the formation of the corresponding benzaldehydes. The reaction is first order with respect to BAB, the alcohol, and hydrogen ions. The reaction exhibits a primary kinetic isotope effect (kH/kD = 5.26). The value of the solvent isotope effect, k(H2O)/k(D2O), equals 0.43 at 298 K. Addition of benzenesulfonamide has no effect on the rate. Increase in amount of acetic acid in the solvent increases the rate. The reaction rate has been determined at five different temperatures and the activation parameters have been calculated. (PhSO2NH2Br)+ has been postulated as the reactive oxidizing species. The rates of oxidation of substituted benzyl alcohols correlate very well with Browns σ+ constants. The value of the reaction constant is −2.84 at 298 K. A hydride transfer from the alcohol to the oxidant, in the rate-determining step, has been proposed.

Kinetics and mechanism of the oxidation of substituted benzylamines by cetyltrimethylammonium permanganate

Oxidation of meta- and para-substituted benzylamines by cetyltrimethylammonium permanganate (CTAP) to the corresponding aldimines is first order with respect to both the amine and CTAP. Oxidation of deuteriated benzylamine (PhCD2NH2) exhibited the presence of a substantial kinetic isotope effect (kH/kD = 5.60 at 293 K). This confirmed the cleavage of an α-C-H bond in the rate-determining step. Correlation analyses of the rates of oxidation of 19 monosubstituted benzylamines were performed with various single and multiparametric equations. The rates of the oxidation showed excellent correlations in terms of Yukawa—Tsuno and Brown’s equations. The polar reaction constants are negative. The oxidation exhibited an extensive cross-conjugation, in the transition state, between the electron-donating substituents and the reaction centre. A mechanism involving a hydride-ion transfer from the amine to CTAP in the rate-determining step has been proposed.

Correlation analysis of reactivity in the addition of substituted benzylamines to benzylidenemalononitrile

The kinetics of addition of a number of ortho-, meta-, and para-substituted benzylamines to benzylidenemalononitrile (BMN) in acetonitrile have been studied. The reaction is first-order with respect to BMN. The order with respect to the amine is more than one. It has been shown that the reaction followed two mechanistic pathways, uncatalyzed and catalyzed by the amine. The enthalpy of activation for the catalyzed path is negative indicating the presence of a preequilibrium (k1, k−1) leading to the formation of a zwitterion. The values of rate constant, k1, for the nucleophilic attack have been determined for twenty-eight benzylamines. The rate constant, k1 was subjected to correlation analyses using various single- and multi-parametric equations. The best correlation is obtained in terms of Chartons LDR and LDRS equations. The polar regression coefficients are negative indicating the formation of a cationic species in the transition state. The reaction is subject to steric hindrance by ortho-substituents.

Correlation analysis of reactivity in the addition of substituted benzylamines to ethyl ?-cyanocinnamate

The kinetics of addition of a number of ortho-, meta-, and para-substituted benzylamines to ethyl α-cyanocinnamate (ECC) in acetonitrile have been studied. The reaction is first-order with respect to the amine and ECC. The rates of reaction of meta- and para-substituted benzylamines showed excellent correlations with Tafts σ1 and σR0, and with σ1 and σRBA values, respectively. The reaction of the ortho-compounds showed a very good correlation with Chartons triparametric equation. The reaction is subject to steric hindrance by the ortho-substituents. A mechanism involving formation of a zwitterionic intermediate in a slow step followed by a fast proton transfer has been proposed.

Kinetics and mechanism of the oxidation of formic and oxalic acids by quinolinium fluorochromate

Kinetics and mechanism of oxidation of formic and oxalic acids by quinolinium fluorochromate (QFC) have been studied in dimethylsulphoxide. The main product of oxidation is carbon dioxide. The reaction is first-order with respect to QFC. Michaelis-Menten type of kinetics were observed with respect to the reductants. The reaction is acid-catalysed and the acid dependence has the form: kobs =a +b[H+]. The oxidation of α-deuterioformic acid exhibits a substantial primary kinetic isotope effect (kH/kD = 6.01 at 303 K). The reaction has been studied in nineteen different organic solvents and the solvent effect has been analysed using Taft’s and Swain’s multiparametric equations. The temperature dependence of the kinetic isotope effect indicates the presence of a symmetrical cyclic transition state in the rate-determining step. Suitable mechanisms have been proposed.