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Heteropoly blues of α-1,2 and α-1,4 isomers of [PV 2 W 10 O 40 ] 5have been prepared by using the electrochemical technique. EPR spectra, measured as a function of temperature over a wide range (20-300 K), are explicable in terms of electronhopping processes in heteropoly blues. Temperature dependence of A || of the isomers suggest that the activation energy for electron hopping is greater for the α-1,4 isomer than the α-1,2 isomer. Other parameters like stability of the blues and intra-molecular electron transfer rate constants are also evaluated using EPR as the tool.

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The second-order rate coefficients for the reactions of ortho-substituted benzoate ions with ethyl bromoacetate have been measured in a 90% acetone-10% water (v/v) mixture at three different temperatures and the results have been compared with those of phenacyl bromide. The order of reactivity of orthosubstituted benzoate ions with ethyl bromoacetate is almost the same as that observed for the reaction of ortho-substituted benzoate ions with phenacyl bromide. Attempts have been made to analyse the rate data in terms of electronic and steric effects b y employing Charton's treatment. Analysis of the results shows that the localized effect is predominant over the delocalized effect in each reaction series and electron-releasing groups favour the reaction and electron-withdrawing groups retard it. The steric term is rate accelerating. The AS* values for all the ortho-substituted benzoate ions are negative and it appears that the bulk effect of the substituent plays a part in the variation of A S .