Kinetic study of acid-catalyzed Knoevenagel condensation between 5-methoxy-1-tetralone and glyoxylic acid

1-tetralone derivatives are compounds of interest due to their diverse biological properties such as antibiotic, anticancer, antioxidant, antiarrhythmic and central nervous system effects. In this work we present, a kinetic study of the Knoevenagel condensation reaction between 5-methoxy-1-tetralone and glyoxylic acid, catalyzed by sulfuric acid, to produce (E)-2-(5-methoxy-1-oxo-3,4-dihydronaphthalen-2(1H)-ylidene)acetic acid. The reaction was carried out in a batch system at 400 rpm for 24 hours at temperatures of 75, 80 and 85 °C. The yields obtained at these temperatures were 90.30, 93.75 and 94.16%, respectively. The reaction was monitored by TLC and HPLC. For the kinetic analysis, three mathematical methods were used: integral, differential and non-linear regression. The results showed an excellent fit of the experimental data to the pseudo-first-order kinetic model. The kinetic parameters calculated at the studied temperatures were: rate constant k=0.0129; 0.0161; 0.0196 (mL/(mmol*min)), activation energy Ea=43.1014 kJ/mol and pre-exponential factor A=8.4608E+03 (mL/(mmol min)). The desired product was purified by recrystallization and characterized using FTIR, GC-MS, ¹H and ¹³C NMR, confirming its structural identity. Acid catalysis significantly improved the kinetics and efficiency of the Knoevenagel condensation reaction between 5-methoxy-1-tetralone and glyoxylic acid, making it an attractive synthetic methodology for the preparation of this class of compounds.