The kinetics and mechanism of the reaction between 4-methoxybenzaldehyde 1, malononitrile 2, and dimedone 3 in the presence of caffeine, 1, 3, 7-trimethylxanthine, as a green catalyst has been spectrally studied in a mixture of water and ethanol as green solvents. Based on the experimental data, the overall order of reaction for the formation of product followed the second order kinetics and under pseudo-order conditions the partial order with respect to 4-methoxybenzaldehyde 1, malononitrile 2

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... and dimedone 3 were one, one and zero, respectively. From the temperature, concentration and solvent studies, the activation energy (E a = 84.35 kJmol -1 ) and the related activation parameters (∆G ‡ = 58.47 ± 1.31 kJmol -1 , ∆S ‡ = 75.45 ± 4.54 Jmol -1 and ∆H ‡ = 81.72 ± 1.31 kJ mol -1 ) were calculated. The first step of the proposed mechanism was recognized as a rate-determining step (k 1 ) and this was confirmed based upon the steady-state approximation.