Kinetics and mechanism of the selective oxidation of benzyl alcohols by acidified dichromate in aqueous acetic acid medium

AbstractThe kinetics of oxidation of a few aliphatic primary alcohols with 1-chlorobenzimidazole (CBI) was studied in aqueous acetic acid medium. The reactions were found to be first order each with respect to the concentrations of CBI and alcohol. The added HClO

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Reactivity of Benzyl Alcohol and Substituted Benzyl Alcohols with 1-Chlorobenzimidazole in Acid Medium – A Kinetic and Mechanistic Approach

IRA-International Journal of Applied Sciences (ISSN 2455-4499) ◽

10.21013/jas.v3.n3.p20 ◽

2016 ◽

Vol 3 (3) ◽

Author(s):

M. Rukmangathan ◽

V. Santhosh Kumar ◽

B. Ramkumar

Keyword(s):

Acetic Acid ◽

Benzyl Alcohol ◽

Acid Medium ◽

Reaction Rates ◽

Effect Of Temperature ◽

Aqueous Acetic Acid ◽

Product Analysis ◽

Acetic Acid Medium ◽

Benzyl Alcohols ◽

Different Temperatures

<div>The kinetics of oxidation of benzyl alcohol and a few substituted benzyl alcohols with 1-chlorobenzimidazole (CBI) were studied in aqueous acetic acid medium. The order of the reactions with respect to each oxidant and substrate was found to be unity. The added HClO4 increases the rate and the order in [HClO4] was found to be fractional. The reactions were catalyzed by NaCl and a fractional order dependence was observed for [NaCl]. The ionic strength had negligible influence on the rate. Increase in the percentage of acetic acid increases the rate. Addition of benzimidazole, one of the products does not affect the rate. Effect of temperature on the reaction rates was studied at different temperatures and the various activation and thermodynamic parameters were computed. The Hammett plot shows an excellent correlation with negative ρ value (- 0.37) for benzyl alcohols. Product analysis shows the formation of aldehydes as major products of oxidation of benzyl alcohols. CBIH+ has been postulated as the reactive oxidizing species. Suitable mechanism and the rate law in consistent with the experimental results have been proposed.</div>

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Perborate Oxidation of Substituted 5-Oxoacids in Aqueous Acetic Acid Medium: A Kinetic and Mechanistic Study

ISRN Physical Chemistry ◽

10.1155/2014/924827 ◽

2014 ◽

Vol 2014 ◽

pp. 1-7 ◽

Cited By ~ 2

Author(s):

S. Shree Devi ◽

B. Muthukumaran ◽

P. Krishnamoorthy

Keyword(s):

Acetic Acid ◽

Acid Medium ◽

Reaction Rate ◽

Reaction Medium ◽

Activation Parameters ◽

Reaction Rates ◽

Mechanistic Study ◽

Aqueous Acetic Acid ◽

Sodium Perborate ◽

Acetic Acid Medium

Kinetics and mechanism of oxidation of substituted 5-oxoacids by sodium perborate in aqueous acetic acid medium have been studied. The reaction exhibits first order both in [perborate] and [5-oxoacid] and second order in [H+]. Variation in ionic strength has no effect on the reaction rate, while the reaction rates are enhanced on lowering the dielectric constant of the reaction medium. Electron releasing substituents in the aromatic ring accelerate the reaction rate and electron withdrawing substituents retard the reaction. The order of reactivity among the studied 5-oxoacids is p-methoxy ≫ p-methyl > p-phenyl > –H > p-chloro > p-bromo > m-nitro. The oxidation is faster than H2O2 oxidation. The formation of H2BO3+ is the reactive species of perborate in the acid medium. Activation parameters have been evaluated using Arrhenius and Eyring’s plots. A mechanism consistent with the observed kinetic data has been proposed and discussed. Based on the mechanism a suitable rate law is derived.

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