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Kinetic study of acid-catalyzed Knoevenagel condensation between 5-methoxy-1-tetralone and glyoxylic acid
* 1 , 1 , 2 , 1
1  Universidad Central del Ecuador, Faculty of Chemical Engineering, Research Group on Food, Organic Compounds, Materials, Applied Microbiology and Energy (ACMME), Ciudadela Universitaria, Quito, Ecuador.
2  Universidad Central del Ecuador, Faculty of Chemical Engineering, Ciudadela Universitaria, Quito, Ecuador.
Academic Editor: Julio A. Seijas

https://doi.org/10.3390/ecsoc-28-20255 (registering DOI)
Abstract:

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.

Keywords: kinetic study; acid catalyzed Knoevenagel condensation; 1-tetralone.
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