Correlation analysis of reactivity in oxidation of some aliphatic aldehydes by 2-picolinium chlorochromate: A kinetic study

The oxidation of six aliphatic aldehydes by 2- picolinium chlorochromate (PICC) in dimethyl sulfoxide (DMSO) leads to the formation of corresponding carboxylic acids. The reaction is of first order each in PICC. A Michaelis-Menten type of kinetics is observed with respect to the aldehydes. The reaction is catalysed by hydrogen ions. The hydrogen-ion dependence has the form: kobs = a + b[H+]. The oxidation of deuteriated acetaldehyde MeCDO exhibited a substantial primary kinetic isotope effect (kH/kD = 5.69 at 298 K). The oxidation of acetaldehyde has been studied in nineteen different organic solvents. The solvent effect has been analysed using Taft's and Swain's multiparametric equations. The rate constants correlate well with Taft’s * values, reaction constants being negative. A mechanism involving transfer of hydride ion 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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The Kinetics of the Oxidation of Acetaldehyde by Acid Permanganate

Zeitschrift für Naturforschung B ◽

10.1515/znb-1972-0710 ◽

1972 ◽

Vol 27 (7) ◽

pp. 772-774 ◽

Cited By ~ 6

Author(s):

K. K. Banerji

Keyword(s):

Isotope Effect ◽

Kinetic Isotope Effect ◽

Activation Parameters ◽

Hydrogen Ion ◽

First Order ◽

Hydride Ion ◽

Kinetic Isotope ◽

Kinetics Of

The kinetics of the oxidation of aceltaldehyde by acid permanganate has been studied. The reaction is of first order with respect to the aldehyde, the oxidant and hydrogen ion individually. The oxidation does not induce polymerisation of acrylonitrile and show a kinetic isotope effect (kH/kD= 6.1). The activation parameters for the oxidation and enolisation reactions have been evaluated. The rate of enolisation, under similar conditions, is less than that of oxidation. A mechanism involving the transfer of a hydride ion from the aldehyde hydrate to the oxidant has been suggested.

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Mechanism of the First Order Decay of 2-Hydroxy-propyl-2-peroxyl Radicals and of O2~ Formation in Aqueous Solution

Zeitschrift für Naturforschung B ◽

10.1515/znb-1977-0811 ◽

1977 ◽

Vol 32 (8) ◽

pp. 886-889 ◽

Cited By ~ 63

Author(s):

Eberhard Bothe ◽

Günther Behrens ◽

Dietrich Schulte-Frohlinde

Keyword(s):

Rate Constant ◽

Rate Constants ◽

Kinetic Isotope Effect ◽

Peroxyl Radicals ◽

Time Resolved ◽

Cyclic Transition ◽

Methyl Substitution ◽

First Order ◽

Kinetic Isotope ◽

Cyclic Transition State

Using time resolved ESR spectroscopy and photoflash conductivity the uncatalysed, first order decay of 2-hydroxy-propyl-2-peroxyl radicals and the uncatalysed, first order generation of O2·̅ and H+ were measured to have the same rate constants. The formation of O2·̅ and H+ was measured in H2O and D2O and a kinetic isotope effect of kH/k =D3.5 was obtained. Comparing the rate constants of the peroxyl radicals derived from methanol, ethanol and 2-propanol it was shown that the rate constant increases with increasing methyl-substitution. In 2-propanol water mixtures the rate constant of the 2-hydroxy-propyl-2-peroxyl radical increases only slightly with increasing polarity of the solvent. The experimental results are in accord with a mechanism which involves a cyclic transition state leading to a concerted elimination of HO2· followed by dissociation into H+ and O2·̅.

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Reactions of trifluoromethyl radicals. V. Hydrogen abstraction from methyl acetate and methyl (2H3)Acetate

Australian Journal of Chemistry ◽

10.1071/ch9801437 ◽

1980 ◽

Vol 33 (7) ◽

pp. 1437

Author(s):

NL Arthur ◽

PJ Newitt

Keyword(s):

Isotope Effect ◽

Rate Constants ◽

Methoxy Group ◽

Methyl Acetate ◽

Kinetic Isotope Effect ◽

Hydrogen Abstraction ◽

Activation Energies ◽

Temperature Range ◽

Kinetic Isotope ◽

Acetyl Group

Hydrogen abstraction by CF3 radicals from CH3COOCH3 and CD3COOCH3 has been studied in the temperature range 78-242°, and data have been obtained for the reactions: CF3 + CH3COOCH3 → CF3H+[C3H5O2] ��(3) CF3 + CH3COOCH3 → CF3H+CH2COOCH3�� (4) CF3 + CD3COOCH3 → CF3D+CD2COOCH3�� (6) CF3 + CD3COOCH3 → CF3H+CD3COOCH2�� (7) The corresponding rate constants, based on the value of 1013.36 cm3 mol-1 S-1 for the recombination of CF3 radicals, are given by (k in cm3 mol-1 s-1 and E in J mol-1): logk3 = (11.52�0.05)-(35430�380)/19.145T �� (3)logk4 = (11.19�0.07)-(34680�550)/19.145T �� (4)logk6 = (11.34�0.06)-(46490�490)/19.145T �� (6)logk7 = (11.26�0.05)-(36440�400)/19.145T �� (7)At 400 K, 59% of abstraction occurs from the acetyl group, and 41 % from the methoxy group. The kinetic isotope effect at 400 K for attack on the acetyl group is 25, due mainly to a difference in activation energies.

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Primary kinetic isotope effect in the gas phase photochlorination of ethyl chloride-1-d1

Canadian Journal of Chemistry ◽

10.1139/v84-147 ◽

1984 ◽

Vol 62 (5) ◽

pp. 899-906 ◽

Cited By ~ 4

Author(s):

Jan Niedzielski ◽

T. Yano ◽

E. Tschuikow-Roux

Keyword(s):

Activation Energy ◽

Gas Phase ◽

Isotope Effect ◽

Ground State ◽

Rate Constants ◽

Kinetic Isotope Effect ◽

Kinetic Isotope ◽

Primary Reference ◽

Hydrogen Deuterium ◽

Increasing Temperature

The abstraction of hydrogen/deuterium from CH3CHDCl by ground state chlorine atoms produced photolytically from Cl2 has been investigated at temperatures betwen 280 and 368 K. The relative rates for the internal competition[Formula: see text]are found to conform to an Arrhenius rate law:[Formula: see text]These data, taken together with the external competition results for the C2H5Cl/CH3CHDCl system, in conjunction with the competitive results using CH4 as a primary reference, have yielded the rate constants (cm3 s−1):[Formula: see text]The relatively weak primary kinetic isotope effect, kH/kD, decreases with increasing temperature from 1,855 at 280 K to 1.66 at 365 K. The results are compared with those obtained based on the BEBO method. While both the trend and the magnitude of the kinetic isotope effect are satisfactorily predicted, the activation energy is not.

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Absolute rate constants for hydrocarbon autoxidation. 25. Rate constants for hydrogen atom abstraction from alkanes by the tert-butylperoxy radical

Canadian Journal of Chemistry ◽

10.1139/v78-498 ◽

1978 ◽

Vol 56 (24) ◽

pp. 3047-3053 ◽

Cited By ~ 33

Author(s):

J. H. B. Chenier ◽

S. B. Tong ◽

J. A. Howard

Keyword(s):

Hydrogen Atom ◽

Rate Constants ◽

Kinetic Isotope Effect ◽

Peroxy Radical ◽

Hydrogen Atom Abstraction ◽

Labile Hydrogen ◽

Absolute Rate ◽

Steric Strain ◽

Kinetic Isotope ◽

Tert Butyl Hydroperoxide

Rate constants for abstraction of secondary and tertiary hydrogens from structurally different alkanes by the tert-butylperoxy radical in solution at 30 °C have been determined by competitive experiments in the presence of tert-butyl hydroperoxide. Rate constants fall in the range 1 × 10−4to 9 × 10−4and 1 × 10−3–2 × 10−2 M−1 s−1 for secondary and tertiary aliphatic C—H bonds, respectively. The most reactive secondary hydrogen is, therefore, almost as reactive as the least reactive tertiary hydrogen. Differences in reactivity within a type of aliphatic C—H bond are governed by differences in steric hindrance to attack by the peroxy radical and by relief of steric strain upon removal of the labile hydrogen. Rate constants for reaction of perdeuterated methylcyclohexane and 3-methylpentane are much smaller than the values calculated from the maximum primary kinetic isotope effect for this reaction.

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ORTHO PARTICIPATION IN THE CONVERSION OF syn-BENZALDOXIME ESTERS TO NITRILES

Canadian Journal of Chemistry ◽

10.1139/v65-443 ◽

1965 ◽

Vol 43 (12) ◽

pp. 3178-3187 ◽

Cited By ~ 10

Author(s):

Robert J. Crawford ◽

Charles Woo

Keyword(s):

Isotope Effect ◽

Kinetic Isotope Effect ◽

Alcoholic Solution ◽

First Order ◽

Rate Determining Step ◽

First Order Kinetics ◽

Kinetic Isotope ◽

Marked Enhancement

Substituted syn-benzaldoxime esters are transformed, in an alcoholic solution, to the corresponding nitriles according to first-order kinetics. All ortho substituents were observed to accelerate the rate of nitrile formation relative to the corresponding para derivative. While the ko/kp ratios for the bromo, chloro, fluoro, methoxy, and methyl substituents fall within the range of 2 to 9, the iodo and methylthio substituents are 119 and 11 000 respectively. Isotopic replacement of the aldoximino hydrogen by deuterium gives rise to a kinetic isotope effect, kH/kD being 5.21 for syn-o-chlorobenzaldoxime p-toluenesulfonate, 1.22 for syn-o-iodobenzaldoxime p-toluenesulfonate, and 1.23 for syn-o-methylthiobenzaldoxime o-iodobenzoate. The marked enhancement of rate and the absence of an appreciable isotope effect are considered to be associated with sulfur and iodine participation in the rate-determining step. A mechanism which is capable of explaining the results observed is suggested.

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Kinetics and Mechanism of the Decarboxylation of Pyrrole-2-carboxylic Acid in Aqueous Solution

Canadian Journal of Chemistry ◽

10.1139/v71-172 ◽

1971 ◽

Vol 49 (7) ◽

pp. 1032-1035 ◽

Cited By ~ 20

Author(s):

G. E. Dunn ◽

Gordon K. J . Lee

Keyword(s):

Aqueous Solution ◽

Ionic Strength ◽

Carboxylic Acid ◽

Isotope Effect ◽

Anthranilic Acid ◽

Kinetic Isotope Effect ◽

Pyrrole Ring ◽

First Order ◽

Kinetic Isotope ◽

Ph Range

The decarboxylation of pyrrole-2-carboxylic acid in aqueous buffers at 50° and ionic strength 1.0 has been found to be first order with respect to substrate at a fixed pH. As the pH is decreased, the rate constant increases slightly in the pH range 3–1, then rises rapidly from pH 1 to 10 M HCl. The 13C-carboxyl kinetic isotope effect is 2.8% in 4 M HClO4 and negligible at pH ~ 3. These observations can be accounted for by a mechanism, previously proposed for the decarboxylation of anthranilic acid, in which the species undergoing decarboxylation is the carboxylate ion protonated at the 2-position of the pyrrole ring. This intermediate can be formed both by ring-protonation of the carboxylate anion and by ionization of the ring-protonated acid. At low acidities ring-protonation is rate determining, but at higher acidities the rate of protonation exceeds that of decarboxylation.

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Article

Canadian Journal of Chemistry ◽

10.1139/v99-099 ◽

1999 ◽

Vol 77 (5-6) ◽

pp. 1085-1096 ◽

Cited By ~ 18

Author(s):

A M Kuznetsov ◽

Jens Ulstrup

Keyword(s):

Proton Transfer ◽

Isotope Effect ◽

Rate Constants ◽

Bovine Serum ◽

Kinetic Isotope Effect ◽

Hydrogen Transfer ◽

Low Frequency ◽

Specific Rate ◽

Adiabatic Limits ◽

Kinetic Isotope

We discuss a broad theoretical frame for hydrogen transfer in chemical and biological systems. Hydrogen tunnelling, coupling between the tunnel modes and the environment, and fluctuational barrier preparation for hydrogen tunnelling are in focus and given precise analytical forms. Specific rate constants are provided for three limits, i.e., the fully diabatic, the partially adiabatic, and the fully adiabatic limits. These limits are all likely to represent real chemical or biological hydrogen transfer systems. The rate constants are referred particularly to the driving force and temperature dependence of the kinetic isotope effect (KIE). The origin of these correlations is different in the three limits. It is rooted in the tunnel factor and weak excitation of the heavier isotopes in the former two limits, giving a maximum for thermoneutral processes. A new observation is that the adiabatic limit also accords with a KIE maximum for thermoneutral processes but the KIE is here reflected solely in the activation Gibbs free energy differences, in this case rooted in the low-frequency environmental nuclear dynamics. Three systems of biological hydrogen tunnelling, viz. lipoxygenase, yeast alcohol dehydrogenase, and bovine serum amine oxygenase, offer unusual new cases for analysis and have been analysed using the theoretical frames. All the systems show large KIEs and strong indications of hydrogen tunnelling. They also represent different degrees of fluctuational barrier preparation, with lipoxygenase as the most rigid and bovine serum amine oxygenase as the softest system.Key words: generalized Born-Oppenheimer scheme, kinetic isotope effect, gated proton transfer, partially adiabatic proton transfer, proton tunnelling in enzyme catalysis.

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