The oxidation of Mandelic Acids to the corresponding oxoacids with ethylenediammonium dichromate ... more The oxidation of Mandelic Acids to the corresponding oxoacids with ethylenediammonium dichromate (EDDC) in aqueous acetic acid has been studied. The reaction is first order with respect to [EDDC] and less than two order observed for Mandelic acids and [H+]. The oxidation of α-deuteriomandelic acid shows the presence of a primary kinetic isotope effect (kH/kD = 6.01 at 298K). The reaction has been found to be catalyzed by [H+] ions. The various thermodynamic parameters for the oxidation have been reported and discussed along with the validity of the isokinetic relationship. With a negative reaction constant (ρ), the reaction displayed a strong correlation with the Hammett σ values. All of the chosen Mandelic acids are oxidised by the same process, according to the Exner plot.
918-925The oxidation of four vicinal, four non-vicinal diols and one of their monoethers by butyl... more 918-925The oxidation of four vicinal, four non-vicinal diols and one of their monoethers by butyltriphenylphosphonium dichromate (BTPPD), in dimethylsulfoxide (DMSO), resulted in the formation of corresponding hydroxyaldehyde as a main product of the oxidation. The reactions are of first order with respect to BTPPD, however, second order dependence is obtained with respect to each the diol and hydrogen ion. The oxidation of [1,1,2,2-2H4]ethanediol exhibited primary kinetic isotope effect (kH/kD = 6.61 at 298 K). The temperature dependence of the kinetic isotope effect suggested the symmetrical transition state in the rate-determining step. The rate constants of oxidation of four vicinal diols show excellent correlation with Taft’s * values with negative reaction constant, *. The rate of oxidation of ethanediol has been determined in nineteen different solvents. An analysis of the solvent effect indicates the importance of the cation-solvating power of the solvents. A suitable mechan...
Department of Chemistry, M. L. Sukhadia University, Udaipur-313 001, Rajasthan, India E-mail: dpa... more Department of Chemistry, M. L. Sukhadia University, Udaipur-313 001, Rajasthan, India E-mail: dpanday26@gmail.com Manuscript received online 10 October 2020, revised and accepted 21 November 2020 Selective oxidation in dimethyl sulfoxide (DMSO) medium by benzimidazolium dichromate (BIDC) of α-hydroxy acid viz. glycolic and lactic acids, produces corresponding oxoacid. A Michaelis-Menten kind kinetics noticed as for hydroxy acids while unit dependency on rate observed as for BIDC. At non-identical temperatures the formation constants and the rates of decomposition of hydroxy acid-BIDC complexes have been evaluated. Thermodynamic parameters and activation parameters for formation of the complex and break down of the complexes have been determined respectively. The oxidation process accelerates with increase in proton concentration. An α-C-H bond fisson in the rate-controlling step suggested by the deuterium isotope effect. For oxidation of glycolic acid, k<sub>H</sub>/k<...
obtained with respect to each the diol and hydrogen ion. The oxidation of [1,1,2,2- 2 H4]ethanedi... more obtained with respect to each the diol and hydrogen ion. The oxidation of [1,1,2,2- 2 H4]ethanediol exhibited primary kinetic isotope effect ( kH/kD = 6.61 at 298 K). The temperature dependence of the kinetic isotope effect suggested the symmetrical transition state in the rate-determining step. The rate constants of oxidation of four vicinal diols show excellent correlation with Taft’s Σ σ * values with negative reaction constant, ρ * . The rate of oxidation of ethanediol has been determined in nineteen different solvents. An analysis of the solvent effect indicates the importance of the cation-solvating power of the solvents. A suitable mechanism has been postulated involving the formation of chromate ester in a pre-equilibrium.
Department of Chemistry, J. N. V. University, Jodhpur-342 005, Rajasthan, India <em>E-mail ... more Department of Chemistry, J. N. V. University, Jodhpur-342 005, Rajasthan, India <em>E-mail </em>: seema@goraexporrs.com <em>Manuscript received 15 December 2008. accepted 27 April 2009</em> The oxidation of a series of nine a-amino acids by butyltriphenylphosphonium dichromate (BTPPDJ in glacial acetic acid in the presence of toluene p-sulphonic acid (TsOH), leads to the formation of corresponding aldimines. The reactions are of first order with respect to BTPPD whereas the second order dependence is observed with respect to each the amino acid and hydro~en ion. The oxidation of perdeuterioglycine showed the absence of a kinetic isotope effect (<em>k</em><sub>H</sub>/<em>k</em><sub>D</sub> = 1.01 at 308 K). The reactions showed an excellent correlation with Taft's σ* substituent constants. the reaction constant being negative. The oxidation of alanine was studied in nineteen different organic solvents. The s...
The oxidation of Mandelic Acids to the corresponding oxoacids with ethylenediammonium dichromate ... more The oxidation of Mandelic Acids to the corresponding oxoacids with ethylenediammonium dichromate (EDDC) in aqueous acetic acid has been studied. The reaction is first order with respect to [EDDC] and less than two order observed for Mandelic acids and [H+]. The oxidation of α-deuteriomandelic acid shows the presence of a primary kinetic isotope effect (kH/kD = 6.01 at 298K). The reaction has been found to be catalyzed by [H+] ions. The various thermodynamic parameters for the oxidation have been reported and discussed along with the validity of the isokinetic relationship. With a negative reaction constant (ρ), the reaction displayed a strong correlation with the Hammett σ values. All of the chosen Mandelic acids are oxidised by the same process, according to the Exner plot.
918-925The oxidation of four vicinal, four non-vicinal diols and one of their monoethers by butyl... more 918-925The oxidation of four vicinal, four non-vicinal diols and one of their monoethers by butyltriphenylphosphonium dichromate (BTPPD), in dimethylsulfoxide (DMSO), resulted in the formation of corresponding hydroxyaldehyde as a main product of the oxidation. The reactions are of first order with respect to BTPPD, however, second order dependence is obtained with respect to each the diol and hydrogen ion. The oxidation of [1,1,2,2-2H4]ethanediol exhibited primary kinetic isotope effect (kH/kD = 6.61 at 298 K). The temperature dependence of the kinetic isotope effect suggested the symmetrical transition state in the rate-determining step. The rate constants of oxidation of four vicinal diols show excellent correlation with Taft’s * values with negative reaction constant, *. The rate of oxidation of ethanediol has been determined in nineteen different solvents. An analysis of the solvent effect indicates the importance of the cation-solvating power of the solvents. A suitable mechan...
Department of Chemistry, M. L. Sukhadia University, Udaipur-313 001, Rajasthan, India E-mail: dpa... more Department of Chemistry, M. L. Sukhadia University, Udaipur-313 001, Rajasthan, India E-mail: dpanday26@gmail.com Manuscript received online 10 October 2020, revised and accepted 21 November 2020 Selective oxidation in dimethyl sulfoxide (DMSO) medium by benzimidazolium dichromate (BIDC) of α-hydroxy acid viz. glycolic and lactic acids, produces corresponding oxoacid. A Michaelis-Menten kind kinetics noticed as for hydroxy acids while unit dependency on rate observed as for BIDC. At non-identical temperatures the formation constants and the rates of decomposition of hydroxy acid-BIDC complexes have been evaluated. Thermodynamic parameters and activation parameters for formation of the complex and break down of the complexes have been determined respectively. The oxidation process accelerates with increase in proton concentration. An α-C-H bond fisson in the rate-controlling step suggested by the deuterium isotope effect. For oxidation of glycolic acid, k<sub>H</sub>/k<...
obtained with respect to each the diol and hydrogen ion. The oxidation of [1,1,2,2- 2 H4]ethanedi... more obtained with respect to each the diol and hydrogen ion. The oxidation of [1,1,2,2- 2 H4]ethanediol exhibited primary kinetic isotope effect ( kH/kD = 6.61 at 298 K). The temperature dependence of the kinetic isotope effect suggested the symmetrical transition state in the rate-determining step. The rate constants of oxidation of four vicinal diols show excellent correlation with Taft’s Σ σ * values with negative reaction constant, ρ * . The rate of oxidation of ethanediol has been determined in nineteen different solvents. An analysis of the solvent effect indicates the importance of the cation-solvating power of the solvents. A suitable mechanism has been postulated involving the formation of chromate ester in a pre-equilibrium.
Department of Chemistry, J. N. V. University, Jodhpur-342 005, Rajasthan, India <em>E-mail ... more Department of Chemistry, J. N. V. University, Jodhpur-342 005, Rajasthan, India <em>E-mail </em>: seema@goraexporrs.com <em>Manuscript received 15 December 2008. accepted 27 April 2009</em> The oxidation of a series of nine a-amino acids by butyltriphenylphosphonium dichromate (BTPPDJ in glacial acetic acid in the presence of toluene p-sulphonic acid (TsOH), leads to the formation of corresponding aldimines. The reactions are of first order with respect to BTPPD whereas the second order dependence is observed with respect to each the amino acid and hydro~en ion. The oxidation of perdeuterioglycine showed the absence of a kinetic isotope effect (<em>k</em><sub>H</sub>/<em>k</em><sub>D</sub> = 1.01 at 308 K). The reactions showed an excellent correlation with Taft's σ* substituent constants. the reaction constant being negative. The oxidation of alanine was studied in nineteen different organic solvents. The s...
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