Younes Ghalandarzehi - Department of Chemistry, Faculty of Science, University of Sistan and Baluchestan, Zahedan, Iran
Sayyed Mostafa Habibi-Khorassani - Department of Chemistry, Faculty of Science, University of Sistan and Baluchestan, Zahedan, Iran
Halime Kord Tamandani - Department of Chemistry, Faculty of Science, University of Sistan and Baluchestan, Zahedan, Iran
Mehdi Shahraki - Department of Chemistry, Faculty of Science, University of Sistan and Baluchestan, Zahedan, Iran

In this study for the first time, kinetics and mechanism of reaction between 4-methoxybenzaldehyde 1,malononitrile 2, and dimedone 3 in the presence of caffeine as a catalystusing conventional UV/visspectrophotometry has been reported. Based on the data which has been obtained from experimentalstudy, the overall order of the reaction is two. The second-order rate constant dependency on thetemperature was in agreement with the Arrhenius and Eyring equations.The kinetic and thermodynamicparameters of the reaction have been calculated. Furthermore, useful information was obtained fromstudies of the effect of solvent and concentration of reactants on the reaction rate. The results showed thatthe second step of the reaction mechanism is a rate-determining step (RDS). The proposed mechanismwas also confirmed according to the obtained results and the steady state approximation. In the kineticsstudy, activation energy and other parameters (Ea, ΔHffi, ΔSffi and ΔGffi) were determined.

Kinetics;4-methoxybenzaldehyde; caffeine; dimedone;UV/vis spectrophotometry