Abstract

Halimeh Yaghoubian, Sayyed Mostafa Habibi-Khorassani* and Ali Ebrahimi

DOI : http://dx.doi.org/10.13005/ojc/310431

This article was conducted to investigate spectrophotometrically the kinetic and mechanism of the reaction synthesis of tetrahydrobenzo[b] pyrans via one-pot, three-component condensation of malononitrile, dimedone and 4-chlorobenzaldehyde in the presence of caffeine, as a new green catalyst. The effect of various parameters such as temperature, solvent, concentration and catalyst was determined. Pursuant to obtained data the reaction rate was obeyed second order kinetics and automatically calculated rate constants were in agreement with the Arrhenius and Eyring equations. From these the activation parameters (Ea, ΔG^‡, ΔS^‡, and ΔH^‡) were determined. Also, in a mixture of water: ethanol (2:1), the rate constant was increased with respect to ethanol solvent that has lower dielectric constant. Furthermore, experimental data and steady state approximation corroborated the proposed mechanism. The results showed that the first step of the reaction mechanism is a rate determining step (RDS).

Kinetics; Mechanism; Tetrahydrobenzo[b]pyran; spectrophotometry technique

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