Kabilan, S.; Girija, R.; Reis, Joao Carlos R.; Segurado, Manuel A. P.; Gomes de Oliveira, Jaime D. published the artcile< Oxidation of benzyl alcohol by pyridinium dichromate in acetonitrile. Using the para/meta ratio of substituent effects for mechanism elucidation>, Reference of 112-63-0, the main research area is benzyl alc pyridinium dichromate oxidation kinetics mechanism LFER.
Rate constants were measured for the oxidation reaction of benzyl alc. and twenty-five ortho-, meta- and para-monosubstituted derivatives in the temperature range 293-323 K at intervals of 10 K. The kinetics were followed spectrophotometrically in dry acetonitrile acidified with trichloroacetic acid (TCA) using pyridinium dichromate (PDC) as oxidizing agent under pseudo-first-order conditions with respect to PDC. Benzaldehyde is the only oxidation product and no reaction takes place without TCA. From good linear Eyring plots activation enthalpies Δ‡H° and entropies Δ‡S° are calculated For ortho-substituted benzyl alcs. high Δ‡H° values and small neg. Δ‡S° values point to an ortho effect on the rate-determining step. Using the tetralinear approach to substituent effects, the average value -λ=1.09 ± 0.05 for the para/meta ratio of inductive or Electra effects is obtained and neg. Hammett reaction constants decreasing in magnitude with increasing temperature are found. A mechanism implicating the prior acid-catalyzed formation of neutral benzyl hydrogen dichromate ester followed by intramol. proton transfer is proposed. Modeling of parameter λ in terms of the electrostatic theory showed its exptl. value to be consistent with the ratio of elec. potentials generated in the immediate vicinity of the nearest chromium atom by dipolar substituents introduced in the aromatic ring on para and meta positions. At a mol. level the oxidative, rate-determining step is suggested to be triggered by the retraction or shrinkage of electron pairs from sigma bonds in Cr2VI species to non-bonding orbitals in unstable CrIV-O-CrVI species. In contrast with past interpretations, an electrochem. approach is used to explain neg. values for the Hammett reaction constant
Journal of the Chemical Society, Perkin Transactions 2 published new progress about Activation enthalpy. 112-63-0 belongs to class esters-buliding-blocks, and the molecular formula is C19H34O2, Reference of 112-63-0.
Referemce:
Ester – Wikipedia,
Ester – an overview | ScienceDirect Topics