Transition-state structure in thermal β-cis-elimination of esters

Kwart, Harold; Slutsky, Joel

doi:10.1039/c39720001182

Cited by 35 publications

(25 citation statements)

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“…Kwart and Nickle [16] have shown that a dependence of on tem-k /k H D perature can be successfully employed to determine whether the loss of hydrogen proceeds through a concerted cyclic process or by an acyclic one. The data for protio and deuterioethanediols (Table III) equal to the zero-point energy difference for the respective C 9 H and C 9 D bonds and (Ϸ 4.5 kJ/mol) the frequency factors and entropies of activation of the respective reactions are nearly equal [17,18]. Similar phenomena were observed earlier in the oxidation of benzhydrol by PBC [1] and that of diols by PFC [6].…”

Section: Mechanismsupporting

confidence: 77%

Kinetics and mechanism of the oxidation of diols by pyridinium bromochromate

Rao

Suri

Kothari

et al. 1998

Int. J. Chem. Kinet.

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The kinetics of oxidation of four vicinal diols, four nonvicinal diols, and one of their monoethers by pyridinium bromochromate (PBC) have been studied in dimethyl sulfoxide. The main product of oxidation is the corresponding hydroxyaldehyde. The reaction is first-order with respect to each the diol and PBC. The reaction is acid-catalyzed and the acid dependence has the form:The oxidation of [1,1,2,2-2 H 4 ]ethanediol exhibitedobs a primary kinetic isotope effect ( at ). The reaction has been studied in 19 k /k ϭ 6.70 298 K H D organic solvents including dimethyl sulfoxide and the solvent effect has been analyzed using multiparametric equations. The temperature dependence of the kinetic isotope effect indicates the presence of a symmetrical transition state in the rate-determining step. A suitable mechanism has been proposed.

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Section: Mechanismsupporting

confidence: 77%

Kinetics and mechanism of the oxidation of diols by pyridinium bromochromate

Rao

Suri

Kothari

et al. 1998

Int. J. Chem. Kinet.

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“…This directly corresponds to the properties of a symmetrical transition state. 22,23 Similar phenomenon have been observed earlier in the oxidation of alcohols by BTPPD. 24 Bordwell 25 has given cogent evidence against the occurrence of concerted one-step bimolecular process of hydrogen transfer and it is clear that in the present reaction also, the hydrogen transfer does not occur by an acyclic bimolecular process.…”

Section: Mechanismsupporting

confidence: 72%

Kinetics and Mechanism of the Oxidation of Aliphatic Aldehydes by Benzimidazolium Dichromate

Kumar¹,

Panday²,

Kothari³

2011

Croat. Chem. Acta

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Abstract. Kinetic and mechanistic studies of the oxidation of aliphatic aldehydes, (in organic non-aqueous solvents), were discussed with an emphasis of correlation of structure and reactivity. The reactions were of first order with respect to BIDC and hydrogen-ion. However, Michaelis-Menten type kinetics were observed with respect to aldehyde. The deuterium isotope effect for the oxidation of acetaldehyde (k H /k D = 6.36 at 298 K) indicated an α-C-H bond cleavage in the rate-determining step. Based on kinetic data, analyses of the solvent effect and results of structure-reactivity correlation along with some nonkinetic parameters suggested a mechanism involving rate-determining oxidative decomposition of a aldehyde-BIDC complex via a cyclic transition state to give a carbocationic species through hydride-ion transfer from the aldehyde to the oxidant. (doi: 10.5562/cca1694)

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“…The data for protio-and deuteriomandelic acids, fitted to the familiar expression k H /k D = A H /A D exp(E a /RT) [22,23], show a direct correspondence with the properties of a symmetrical transition state in which the activation energy difference (E a ) for k H /k D is equal to the zero-point energy difference for the respective C H and C D bonds (≈4.5 kJ/mol) and the entropies of activation of the respective reactions are nearly equal. Similar phenomena were observed earlier in the oxidation of alcohols by quinolinium bromochromate [24] and that of hydroxy acids by PFC [25].…”

Section: Mechanismsmentioning

confidence: 99%

Oxidation of some α‐hydroxy acids by tetraethylammonium chlorochromate: A kinetic and mechanistic study

Swami

Yajurvedi

Mishra

et al. 2009

Int J of Chemical Kinetics

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The oxidation of glycolic, lactic, malic, and a few substituted mandelic acids by tetraethylammonium chlorochromate (TEACC) in dimethylsulfoxide leads to the formation of corresponding oxoacids. The reaction is first order each in TEACC and hydroxy acids. Reaction is failed to induce the polymerization of acrylonitrile. The oxidation of α-deuteriomandelic acid shows the presence of a primary kinetic isotope effect (k H /k D = 5.63 at 298 K). The reaction does not exhibit the solvent isotope effect. The reaction is catalyzed by the hydrogen ions. The hydrogen ion dependence has the following form:Oxidation of p-methylmandelic acid has been studied in 19 different organic solvents. The solvent effect has been analyzed by using Kamlet's and Swain's multiparametric equations. A mechanism involving a hydride ion transfer via a chromate ester is proposed. C 2009 Wiley Periodicals, Inc. Int J Chem Kinet 42: 50-55, 2010

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Transition-state structure in thermal β-cis-elimination of esters

Abstract: Tinpublished results of S. Sarner and J. Slutsky from these laboratories to be presented in a future article

Cited by 35 publications

References 0 publications

Kinetics and mechanism of the oxidation of diols by pyridinium bromochromate

Kinetics and mechanism of the oxidation of diols by pyridinium bromochromate

Kinetics and Mechanism of the Oxidation of Aliphatic Aldehydes by Benzimidazolium Dichromate

Oxidation of some α‐hydroxy acids by tetraethylammonium chlorochromate: A kinetic and mechanistic study

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