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5.
Mechanistic Study of Palladium(II)-Catalysis in Oxidation of
Cyclohexanol by
N-Chlorosuccinimide in Aqueous Alkaline Medium: A Kinetic Approach
Kumud Lata Singh, Shipra Tripathi, Sandeep Kumar
Mishra and Bharat Singh*
Chemistry Department, University of Allahabad, Allahabad-211 002,
India. E-mail:
bschem_au@yahoo.com
Abstract:
Kinetics of oxidation of cyclohexanol by N-chlorosuccinimide (NCS)
in the presence of alkaline solution of palladous chloride has
been investigated at 35°C. The results indicate first order
kinetics with respect to [NCS]. First order dependence of the
reaction on [cyclohexanol] and [Pd(II)] at their lower
concentrations tends to zero order in their higher concentration
range. Zero order kinetics with respect to [OH¯] was observed.
Initial addition of succinimide (NHS) decreases the rate.
Negligible effect of increase in ionic strength of medium and [Cl¯]
on the rate constant was observed. A complex [(OH)3HO-----Pd-----OHCHR2]2-,
formed between reactive species of Pd(II) and cyclohexanol prior
to slow and rate determining step, is suggested. The rate law
derived on the basis of proposed mechanistic steps conforms to
all the observed kinetic results.
Keywords: Pd(II) catalysis, oxidation, cyclohexanol, N-chlorosuccinimide,
NaOH,
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