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12.
Mechanism of Pd (II) Catalysis in Potassium Bromate Oxidation of
Diethanolamine and Triethanolamine in Alkaline Solution: A Kinetic
and Environmentally Benign Studies
Bharat Singh*, Anamika Singh, Aniruddh Kumar Singh and Shipra
Tripathi
Chemical Kinetics Laboratories, Department of Chemistry, University
of Allahabad,
Allahabad-211 002 (India), *For correspondence Email:
bschem_au@yahoo.com
Abstract:
Kinetic and mechanistic studies of Pd(II) catalysis in oxidation
of diethanolamine (DEA) and triethanolamine (TEA) by alkaline
solution of potassium bromate at 35°C have been carried out. The
results indicated first order kinetics with respect to both
[KBrO3] and [Pd(II)] in oxidation of DEA and TEA.
First order dependence on both DEA and TEA was observed in their
concentration range from 1.00 ×10-2 to 2.5 ×10-2
mol dm-3 but beyond this on increasing their
concentration up to 5.00 ×10-2 mol dm-3,
first order kinetics tended to zero order in [DEA] and [TEA].
Positive effect of [OH¯] and negligible effect of variation of
ionic strength of the medium on rate of oxidation of both amino
alcohols were observed. Successive effect of addition of KCl
decreased the rate showing negative effect of [Cl¯] on the rate
of oxidation of aminoalcohols. Variation of [Hg(OAc)2]
did not bring about any change in the rate constant, indicating
its limited role as bromide ion scavenger. Rate constant
measured at 30, 35, 40 and 45 °C led to calculate activation
parameters. Acetic acid and ammonia were identified as main
oxidation products. A tentative mechanism involving the
formation of a complex between BrO3¯ ion and [Pd(II)-amino
alcohol] complex prior to rate controlling step is suggested.
Keywords: Kinetics, Mechanism, KBrO3, Pd(II),
Diethanolamine, Triethanolamine.
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