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

The oxidation of six methyl aryl ketones by acid permanganate has been studied, in the presence of fluoride ions. The products of the oxidation are formaldehyde and the corresponding benzoic acids.The oxidation is first order with respect to each the ketone, the oxidant and hydrogen ions. The reaction rate increases sharply with the increase in the amount of acetic acid in the solvent. The oxidation of acetophenone exhibits the kinetic isotope effect, kH/kD = 4.60 at 30�C. The solvent isotope effect is given by k(D2O)/k(H2O) = 5.03. The acid-catalysed enolization rate of the ketones has been measured by the bromination method. The activation parameters for both the oxidationand enolization reactions have been evaluated. The oxidation is slower than the acid-catalysed enolization. The relative rates of the oxidation are proportional to the relative rates of enolization.These results coupled with the magnitude of the solvent isotope effect suggest that the enol form of the ketone is involved in the oxidation process. A possible mechanism has been suggested.

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Kinetics and Mechanism of the Oxidation of Some α-Hydroxyacids by Morpholinium Chlorochromate

Progress in Reaction Kinetics and Mechanism ◽

10.3184/146867808x379300 ◽

2008 ◽

Vol 33 (4) ◽

pp. 393-405

Author(s):

Neha Malani ◽

Manju Baghmar ◽

Preeti Swami ◽

Pradeep Kumar Sharma

Keyword(s):

Isotope Effect ◽

Kinetic Isotope Effect ◽

Ion Transfer ◽

Hydrogen Ions ◽

Solvent Isotope Effect ◽

First Order ◽

Hydride Ion ◽

Kinetic Isotope ◽

Solvent Isotope ◽

Hydride Ion Transfer

The oxidation of glycollic, lactic, malic and a few substituted mandelic acids by morpholinium chlorochromate (MCC) in dimethylsulfoxide (DMSO) leads to the corresponding oxoacids. The reaction is first order each in MCC and hydroxyacid. The reaction failed to induce the polymerisation of acrylonitrile. The oxidation of α–deuteriomandelic acid shows a primary kinetic isotope effect ( kH/ kD = 5.63 at 298 K) but does not exhibit a solvent isotope effect. The reaction is catalysed by hydrogen ions according to: kobs = a + b[H+]. The oxidation of p-methyl mandelic acid has been studied in 19 different organic solvents and the solvent effect analysed using Kamlet's and Swain's multiparametric equations. A mechanism involving a hydride ion transfer via a chromate ester is proposed.

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Kinetics and Mechanism of the Oxidation of α-Hydroxy Carboxylic Acids by Bromine

Zeitschrift für Naturforschung B ◽

10.1515/znb-1973-7-812 ◽

1973 ◽

Vol 28 (7-8) ◽

pp. 450-453 ◽

Cited By ~ 1

Author(s):

Kalyan K. Banerji

Keyword(s):

Isotope Effect ◽

Hydroxy Acid ◽

Kinetic Isotope Effect ◽

Activation Parameters ◽

Probable Mechanism ◽

Molecular Bromine ◽

Solvent Isotope Effect ◽

First Order ◽

Kinetic Isotope ◽

Solvent Isotope

The oxidation of glycollic, lactic, u-hydroxybutyric, and 2-phenyllactic acids by aqueous bromine has been studied. The reaction is of first order with respect to the oxidant and the anion of the hydroxy acid respectively. The active oxidising species is molecular bromine. The oxidation of α,α-dideuterioglycollic acid indicated a kinetic isotope effect, kH/kD=4.62 at 25°C. The reaction does not show any appreciable solvent isotope effect. The activation parameters arc evaluated. A probable mechanism has been suggested.

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pH Dependent Mechanisms of Hydrolysis of 4-Nitrophenyl β-D-Glucoside

10.26434/chemrxiv.13735084.v3 ◽

2021 ◽

Author(s):

Amani Alhifthi ◽

Spencer Williams

Keyword(s):

Isotope Effect ◽

Nucleophilic Aromatic Substitution ◽

Aromatic Substitution ◽

Solvent Isotope Effect ◽

Dissociative Mechanism ◽

Neighboring Group ◽

Rate Determining Step ◽

Solvent Isotope ◽

A Minor ◽

Hydrolysis Of

1,2-trans-Glycosides hydrolyze through different mechanisms at different pH values, but systematic studies are lacking. Here we report the pH-rate constant profile for the hydrolysis of 4-nitrophenyl β-D-glucoside. An inverse kinetic isotope effect (k(H3O+)/k(D3O+) = 0.63) in the acidic region indicates that the mechanism requires the formation of the conjugate acid of the substrate for the reaction to proceed, with heterolytic cleavage of the glycosidic C-O bond. Reactions in the pH-independent region exhibit general catalysis with a single proton in flight, a normal solvent isotope effect of kH/kD = 1.5, and when extrapolated to zero buffer concentration show a small solvent isotope effect k(H2O)/k(D2O) = 1.1, consistent with water attack through a dissociative mechanism. In the basic region, solvolysis in 18O-labelled water and H2O/MeOH mixtures allowed detection of bimolecular hydrolysis and neighboring group participation, with a minor contribution of nucleophilic aromatic substitution. Under mildly basic conditions, a bimolecular concerted mechanism is implicated through an inverse solvent isotope effect of k(HO–)/k(DO–) = 0.5 and a strongly negative entropy of activation (DS‡ = –13.6 cal mol–1 K–1). Finally, at high pH, an inverse solvent isotope effect of k(HO–)/k(DO–) = 0.6 indicates that the formation of 1,2-anhydrosugar is the rate determining step.

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Unimolecular, bimolecular and intramolecular hydrolysis mechanisms of 4-nitrophenyl β-D-glucopyranoside

10.26434/chemrxiv.13735084.v6 ◽

2021 ◽

Author(s):

Amani Alhifthi ◽

Spencer Williams

Keyword(s):

Isotope Effect ◽

Nucleophilic Aromatic Substitution ◽

Aromatic Substitution ◽

Solvent Isotope Effect ◽

Dissociative Mechanism ◽

Neighboring Group ◽

Rate Determining Step ◽

Conjugate Acid ◽

Solvent Isotope ◽

A Minor

1,2-trans-Glycosides hydrolyze through different mechanisms at different pH values, but systematic studies are lacking. Here we report the pH-rate constant profile for the hydrolysis of 4-nitrophenyl β-D-glucoside. An inverse kinetic isotope effect of k(H3O+)/k(D3O+ = 0.65 in the acidic region indicates that the mechanism requires the formation of the conjugate acid of the substrate for the reaction to proceed, with heterolytic cleavage of the glycosidic C-O bond. Reactions in the pH-independent region exhibit general catalysis with a single proton in flight, a normal solvent isotope effect of kH/kD = 1.5, and when extrapolated to zero buffer concentration show a small solvent isotope effect k(H2O)/k(D2O) = 1.1, consistent with water attack through a dissociative mechanism. In the basic region, solvolysis in 18O-labelled water and H2O/MeOH mixtures allowed detection of bimolecular hydrolysis and neighboring group participation, with a minor contribution of nucleophilic aromatic substitution. Under mildly basic conditions, a bimolecular concerted mechanism is implicated through an inverse solvent isotope effect of k(HO–)/k(DO–) = 0.5 and a strongly negative entropy of activation (DS‡ = –13.6 cal mol–1 K–1). Finally, at high pH, an inverse solvent isotope effect of k(HO–)/k(DO–) = 0.6 indicates that the formation of 1,2-anhydrosugar is the rate determining step.

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Isotope Effects in Proton-transfer Reactions. VII. Deuterium Solvent Isotope Effect and Primary Kinetic Isotope Effect on the Racemization of 2-Phenylpropionitrile in Methanol/Methanol-O-d.

Acta Chemica Scandinavica ◽

10.3891/acta.chem.scand.30a-0421 ◽

1976 ◽

Vol 30a ◽

pp. 421-424 ◽

Cited By ~ 1

Author(s):

Nils-Åke Bergman ◽

Inger Källson ◽

Kari Neuvonen ◽

Raimo Keskinen ◽

M. Sandström

Keyword(s):

Proton Transfer ◽

Isotope Effect ◽

Kinetic Isotope Effect ◽

Isotope Effects ◽

Transfer Reactions ◽

Solvent Isotope Effect ◽

Kinetic Isotope ◽

Proton Transfer Reactions ◽

Solvent Isotope

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pH-Rate Profile for Hydrolysis of 4-Nitrophenyl β-D-Glucopyranoside: Unimolecular, Bimolecular and Intramolecular Cleavage Mechanisms

10.26434/chemrxiv.13735084.v5 ◽

2021 ◽

Author(s):

Amani Alhifthi ◽

Spencer Williams

Keyword(s):

Isotope Effect ◽

Nucleophilic Aromatic Substitution ◽

Aromatic Substitution ◽

Solvent Isotope Effect ◽

Dissociative Mechanism ◽

Neighboring Group ◽

Rate Determining Step ◽

Rate Profile ◽

Solvent Isotope ◽

Hydrolysis Of

1,2-trans-Glycosides hydrolyze through different mechanisms at different pH values, but systematic studies are lacking. Here we report the pH-rate constant profile for the hydrolysis of 4-nitrophenyl β-D-glucoside. An inverse kinetic isotope effect of k(H3O+)/k(D3O+ = 0.65 in the acidic region indicates that the mechanism requires the formation of the conjugate acid of the substrate for the reaction to proceed, with heterolytic cleavage of the glycosidic C-O bond. Reactions in the pH-independent region exhibit general catalysis with a single proton in flight, a normal solvent isotope effect of kH/kD = 1.5, and when extrapolated to zero buffer concentration show a small solvent isotope effect k(H2O)/k(D2O) = 1.1, consistent with water attack through a dissociative mechanism. In the basic region, solvolysis in 18O-labelled water and H2O/MeOH mixtures allowed detection of bimolecular hydrolysis and neighboring group participation, with a minor contribution of nucleophilic aromatic substitution. Under mildly basic conditions, a bimolecular concerted mechanism is implicated through an inverse solvent isotope effect of k(HO–)/k(DO–) = 0.5 and a strongly negative entropy of activation (DS‡ = –13.6 cal mol–1 K–1). Finally, at high pH, an inverse solvent isotope effect of k(HO–)/k(DO–) = 0.6 indicates that the formation of 1,2-anhydrosugar is the rate determining step.

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pH Dependent Mechanisms of Hydrolysis of 4-Nitrophenyl β-D-Glucoside

10.26434/chemrxiv.13735084 ◽

2021 ◽

Author(s):

Amani Alhifthi ◽

Spencer Williams

Keyword(s):

Isotope Effect ◽

Nucleophilic Aromatic Substitution ◽

Aromatic Substitution ◽

Solvent Isotope Effect ◽

Dissociative Mechanism ◽

Neighboring Group ◽

Rate Determining Step ◽

Solvent Isotope ◽

A Minor ◽

Hydrolysis Of

1,2-trans-Glycosides hydrolyze through different mechanisms at different pH values, but systematic studies are lacking. Here we report the pH-rate constant profile for the hydrolysis of 4-nitrophenyl β-D-glucoside. An inverse kinetic isotope effect (k(H3O+)/k(D3O+) = 0.63) in the acidic region indicates that the mechanism requires the formation of the conjugate acid of the substrate for the reaction to proceed, with heterolytic cleavage of the glycosidic C-O bond. Reactions in the pH-independent region exhibit general catalysis with a single proton in flight, a normal solvent isotope effect of kH/kD = 1.5, and when extrapolated to zero buffer concentration show a small solvent isotope effect k(H2O)/k(D2O) = 1.1, consistent with water attack through a dissociative mechanism. In the basic region, solvolysis in 18O-labelled water and H2O/MeOH mixtures allowed detection of bimolecular hydrolysis and neighboring group participation, with a minor contribution of nucleophilic aromatic substitution. Under mildly basic conditions, a bimolecular concerted mechanism is implicated through an inverse solvent isotope effect of k(HO–)/k(DO–) = 0.5 and a strongly negative entropy of activation (DS‡ = –13.6 cal mol–1 K–1). Finally, at high pH, an inverse solvent isotope effect of k(HO–)/k(DO–) = 0.6 indicates that the formation of 1,2-anhydrosugar is the rate determining step.

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pH Dependent Mechanisms of Hydrolysis of 4-Nitrophenyl β-D-Glucoside

10.26434/chemrxiv.13735084.v2 ◽

2021 ◽

Author(s):

Amani Alhifthi ◽

Spencer Williams

Keyword(s):

Isotope Effect ◽

Nucleophilic Aromatic Substitution ◽

Aromatic Substitution ◽

Solvent Isotope Effect ◽

Dissociative Mechanism ◽

Neighboring Group ◽

Rate Determining Step ◽

Solvent Isotope ◽

A Minor ◽

Hydrolysis Of

1,2-trans-Glycosides hydrolyze through a range of mechanisms under conditions of different pH, but systematic studies are lacking. Here we report the pH-rate constant profile for the hydrolysis of 4-nitrophenyl β-D-glucoside. An inverse kinetic isotope effect (k(H3O+)/k(D3O+) = 0.63) in the acidic region indicates that the mechanism requires the formation of the conjugate acid of the substrate for the reaction to proceed, with heterolytic cleavage of the glycosidic C-O bond. Reactions in the pH-independent region exhibited general catalysis with a single proton in flight with a normal solvent isotope effect of kH/kD = 1.5, and when extrapolated to zero buffer concentration show a small solvent isotope effect k(H2O)/k(D2O) = 1.1, which is consistent with water attack through a dissociative mechanism. In the basic region, solvolysis in 18O-labelled water and H2O/MeOH mixtures allowed detection of bimolecular hydrolysis and neighboring group participation, and to a minor degree, nucleophilic aromatic substitution. Under mildly basic conditions, a bimolecular dissociative mechanism is implicated through an inverse solvent isotope effect of k(HO–)/k(DO–) = 0.5 and a strongly negative entropy of activation (deltaS‡ = –13.6 cal mol–1 K–1). Finally, at high pH, an inverse solvent isotope effect of k(HO–)/k(DO–) = 0.6 indicates that the formation of 1,2-anhydrosugar is the rate determining step.

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Unimolecular, bimolecular and intramolecular hydrolysis mechanisms of 4-nitrophenyl β-D-glucopyranoside

10.26434/chemrxiv.13735084.v8 ◽

2021 ◽

Author(s):

Amani Alhifthi ◽

Spencer Williams

Keyword(s):

Isotope Effect ◽

Nucleophilic Aromatic Substitution ◽

Aromatic Substitution ◽

Solvent Isotope Effect ◽

Dissociative Mechanism ◽

Neighboring Group ◽

Rate Determining Step ◽

Conjugate Acid ◽

Solvent Isotope ◽

A Minor

1,2-trans-Glycosides hydrolyze through different mechanisms at different pH values, but systematic studies are lacking. Here we report the pH-rate constant profile for the hydrolysis of 4-nitrophenyl β-D-glucoside. An inverse kinetic isotope effect of k(H3O+)/k(D3O)+ = 0.65 in the acidic region indicates that the mechanism requires the formation of the conjugate acid of the substrate for the reaction to proceed, with heterolytic cleavage of the glycosidic C-O bond. Reactions in the pH-independent region exhibit general catalysis with a single proton in flight, a normal solvent isotope effect of kH/kD = 1.5, and when extrapolated to zero buffer concentration show a small solvent isotope effect k(H2O)/k(D2O) = 1.1, consistent with water attack through a dissociative mechanism. In the basic region, solvolysis in 18O-labelled water and H2O/MeOH mixtures allowed detection of bimolecular hydrolysis and neighboring group participation, with a minor contribution of nucleophilic aromatic substitution. Under mildly basic conditions, a bimolecular concerted mechanism is implicated through an inverse solvent isotope effect of k(HO–)/k(DO–) = 0.5 and a strongly negative entropy of activation (DS‡ = –13.6 cal mol–1 K–1). Finally, at high pH, an inverse solvent isotope effect of k(HO–)/k(DO–) = 0.6 indicates that the formation of 1,2-anhydrosugar is the rate determining step.

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