Affiliation:
1. Department of Chemistry, Government College, Kota, 324001, Rajasthan, India
Abstract
Aims:
Oxidation of p-anisaldehyde by Quinolinium dichromate (QDC) in the
aqueous acetic acid medium in the presence of sulphuric acid using surfactants.
Background:
The oxidation studies of anisaldehyde is very important as the oxidized
products are used as a synthetic intermediate for the preparation of a variety of drugs.
Quinolinium dichromate (QDC) has emerged as a very useful and versatile oxidant.
Micellar medium enhances the reaction rate.
Objective:
1. To study the kinetics of the reaction, which includes the determination of
order, rate, and activation parameters. 2. Spectral characterization of QDC by NMR and
the kinetic study of the reaction mechanism is done through UV – A visible
spectrophotometer. 3. Solvent effect for the oxidation of anisaldehyde by QDC. 4.
Determination of critical micelle concentration (CMC) of used surfactants (CTAB and
SDS).
Methods:
The reactions were followed at constant temperature and were followed by
monitoring the UV – Visible spectrophotometer (Double Beam – 2203) in a quartz cuvette
of 1 cm path length by following the absorbance decay of Cr (VI) at 440 nm.
Result:
KINETIC RESULTS: 1. The reaction follows first-order dependence on panisaldehyde
and QDC. 2. The reaction is found to be acid-catalysed. A plot of log [k]
versus log [H+] was found to be a straight line with a slope of 1.07. EFFECT OF
SOLVENT: The rate of reaction increases with the increase in acetic acid proportion in the
medium, which suggests that the reactions were of the ion–dipole type. MICELLAR
EFFECT: 1. Experimental results demonstrated that anionic surfactant SDS catalysed and
accelerated the study more effectively than CTAB, which is a cationic surfactant, and the
rate of reaction increases with an increase in the concentration of the SDS while in the case
of CTAB, the rate decreases with an increase in its concentration. 2. CMC values of CTAB
and SDS were 3.9 mM and 8.2 mM, respectively.
Conclusion:
The value of negative ΔS (entropy of activation) and positive ΔH (enthalpy of
activation) suggests the formation of more ordered activated complexes, and the transition
state is highly solvated. SPECTROSCOPIC ANALYSIS 1.NMR characterisation of
synthesised QDC shows a resemblance with pure QDC. 2. Effect of oxidant QDC, panisaldehyde
and acid was studied by considering the spectra of the reaction mixture and
varying their concentration.
Publisher
Bentham Science Publishers Ltd.
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