oa South African Journal of Chemistry - The reaction of vanadium(v) oxinate and ethanol in dilute concentration in benzene
The kinetics of the reaction between vanadium(V) oxinate and ethanol in dilute concentration in benzene have been investigated at four different temperatures. The reaction was found to be a reversible reaction of the form. A+B C+D and the rate constants, activation energies and actIvation entropies of both thte forward and the reverse reaction are reported, together with the equilibrium constants and the enthalpy of the reaction. The gradual colour change of the black 8-hydroxyquinolate of pentavalent vanadium (vanadium(Y) oxinate;(C,H 60N),VOï¿½OH) in benzene or chlorofonn to red, upon the addition of an alcohol, was first observed by Buscarons et al. 1 in 19-19. In 1953, Bidig and Bayer 2 suggested that this reaction involved a cis-trans isomerisation of the vanadium oxinate, which resulted in the colour change. This explanation was contested by Blair et al. 3 in 1958, who showed that 8-hydroxyquinoline combined with excess of boiling, lower aliphatic alcohols to give red esters, which separated out on cooling to give red, crystalline solids with no hydroxyl bonds in their infrared spectra. On the basis uf equilibrium measurements and kinetic observations carried out in a-dichlorobenzene and using cetyl alcohol, they further concluded
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