A Study on the Kinetics and Mechanism of the One-Pot Formation of 3,4,5-Substituted Furan-2(5H)-Ones in the Presence of Lactic Acid: Effect of Different Substituents

The kinetics of the reaction between para-substituted anilines and dimethyl acetylenedicarboxylate (DMAD) with derivatives of benzaldehyde for the one-pot formation of 3,4,5-substituted furan-2(5H)-ones in the presence of lactic acid as a catalyst have been studied spectrophotometrically at different temperatures. A mechanism involving four steps was proposed for the reactions, all of which followed second-order kinetics. The partial orders with respect to substituted aniline and DMAD were one and one and the reactions revealed zero-order kinetics for benzaldehyde and its derivatives. Changing of substituents on benzaldehyde left rates of reaction unaffected. However, various substituents on aniline showed that para electron-withdrawing groups decreased the rate of reaction. According to investigation of an isokinetic relationship, a common mechanism exists for all studied substituents and a general mechanism can be formulated. Kinetic values (k and Ea) and associated activation parameters (ΔG‡, ΔS‡ and ΔH‡) of the reactions were determined.