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Kinetic and Mechanistic Studies in the Oxidation of Ethanol by P-Methoxy-N-Bromobenzamide

Volume 28, Number 3

M. K. Badole*, L. N. Malviya, K. S. Sariya and V. K. Siriah

Department of Chemistry, Government M.G.M. P.G.College, Itarsi, India.

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ABSTRACT:

Kinetics Studies of The oxidation of Ethanol by p-methoxy-n-bromobenzamide has been made in aqoues acetic acid in the presence of mercuric acetate. The reaction is first order with respect to both, the oxidant and near about are with respect to the substrates. The order with respect to perchloric acid is fractional or first order depending upon the substrate concentration. The reaction is retarded by the initial addition of benzamide and is enhanced by the added potassium bromide. The activation parameters have been calculated and a suitable mechanism has been proposed.

KEYWORDS:

Kinetics; Oxidation; Ethanol; p-Methoxy-n-Bromobenzamide

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Badole M. K, Malviya L. N, Sariya K. S, Siriah V. K. Kinetic and Mechanistic Studies in the Oxidation of Ethanol by P-Methoxy-N-Bromobenzamide. Orient J Chem 2012;28(3).

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Badole M. K, Malviya L. N, Sariya K. S, Siriah V. K. Kinetic and Mechanistic Studies in the Oxidation of Ethanol by P-Methoxy-N-Bromobenzamide. Available from: http://www.orientjchem.org/?p=23150

Introduction

Reports are available in the literature on the mechanism of oxidation by chloramine-T1, chloramine-B2, N-bromosuccinimide3, N-bromobenzamide4-5 p-methyl6 and other halomides, is available but very little is known about the modes of the redox reaction of p-methoxy-N-bromobenzamide (p-MeoNBB) as an oxidant. By substituting benzene ring of such bezamides with different groups it is possible to tune oxidation potential of N-halomides and thereby developing a tuning oxidant, such oxidant are very much usefull in controlling a number of free radical polymerization7-9  reaction and also usefull in different analyting procedures. Further different mechanistic pathways reported for the structurally related N-haloamides10-12 also promoted us to undertake the present investigation.

Experimental

Alcohol used were of S.merck grade and were purified by the method described in the literature .All the chemical used were B.D.H. ‘AR ’and S.M. ‘GR’ quality.   Alcohol were dried over anhydrous magnesium sulphate and then fractionally distilled. Acetic acid was distilled over chromic acid before use. Perchloric acid was use as a source of hydrogen ions. The reaction vessels were coated with black paints to exclude any photochemical effect.  The kinetics of oxidation of alcohol is found to be pseudo. First order reaction by keeping a large excess of alcohol over p-methoxy-N-bromobenzamide. The reactions were followed iodometrically for over 70 % of the reaction. The temperature was kept constant with in + 0.10C .Preliminary experiments showed that the reaction is not sensitive to ionic strength hence no attempt was made to keep it constants.

Results and Discussion

The kinetics of oxidation of alcohol is found to be pseudo first order. A large excess of alcohol was maintained over p- methoxy-N-bromobenzamide. Stoichiometry of the reaction was also studied. It was observed that one equivalent of oxidant was consumed by on equivalent of alcohol.

R-CH2OH + CH3OC6H4NHBr→R–CH3OC6H4NH2 + HBr

Dependence on oxidant concentration: The data are summarized in table -1

 

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