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Esterification of dicarboxylic acids with various alcohols and phenols in presence of metal exchanged montmorillonite clay catalyst (M n+ -mont; M nþ ¼ Al 3þ , Fe 3+ , Cr 3+ , Zn 2+ , Mn 2+ , and Ni 2+ ) is studied. Among the catalysts used, Al 3+ -mont was found to be the most effective, as it gave good to excellent yields of esters under mild reaction conditions. The heterogeneous catalyst presented here can be regenerated and reused. All these features indicate the high potential of the reaction as ''green chemistry'' process.

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Esterification of phenylacetic acid with phenol, cresols, nitrophenols and resorcinol has been carried out in the presence of montmorillonite clay exchanged with H + -ions, Al 3+ -ions and polyhydroxy oligomer cations of Al. Na + -montmorillonite (raw clay) was inactive, H + -and Al 3+ -montmorillonites, dried at 100• C, showed 52 and 67% conversions to ester, respectively, upon refluxing the phenylacetic acid (20 mmol) and p-cresol (40 mmol) for 6 h. While Al 3+ -montmorillonite dried at 200• C showed a conversion of 36% the same catalyst when dried at 400• C showed no conversion. Montmorillonite exchanged with aluminium polyhydroxy oligomers dried at 100 • C and calcined at 500• C to get pillared clay (d0 0 1=17.5Å) failed to bring about the esterification. Effect of concentration of reactants, amount of catalyst and the reaction time on the yield of p-cresyl phenylacetate has been investigated. The esterification of phenylacetic acid with phenol and substituted phenols like m-cresol, o-cresol, p-nitro phenol and o-nitro phenol showed reduced yield due to steric factors. The activity of the clay catalyst after regeneration has also been studied.