Esterificação de álcool bisabolol com ácido mandélico via catálise heterogênea

Abstract

Esterification reactions play an important role in organic chemistry due to their potential for obtaining various products. However, some of these reactions have limitations, such as for tertiary alcohols due to their lower reactivity, lower solubility in water, greater steric hindrance and greater thermal stability. In this work, the esterification reaction of alpha-bisabolol, a tertiary alcohol, with mandelic acid was studied using a catalyst based on alumina oxide and cerium oxide (Al2O3/CeO2). The reaction took place using equimolar quantities of the reactants in a glass reactor at 125ºC for 4 hours. The computational chemistry calculations were carried out in Gaussian 09. Calculations were carried out for the uncatalyzed reaction using the DFT method (B3LYP). The structures of the reactant and product molecules were designed and optimized in Gaussview 5.0, using the semi-empirical method Parametric Method 6 (PM6). The products were monitored and analyzed using thin layer chromatography to follow the formation of the products. The products were separated and isolated by classical liquid chromatography, analyzing the components: product 1, product 2 and the pure alpha bisabolol sample. The products were characterized by mass spectrometry, nuclear magnetic resonance and infrared. The theoretical study showed that under non-standard conditions, ∆G= -1993.76J at 383.15 k (110 ºC), the reaction is spontaneous. The chromatographic and spectroscopic results matched the experimental peaks, the theoretical peaks reported in the literature and the simulated results. In parallel with the esterification reaction, alpha-bisabolol oxide was found as a secondary product. A mechanism was proposed for the esterification reaction of mandelic acid with alpha-bisabolol. Despite the low yield, alpha bisabolol (tertiary alcohol) proved promising for esterification with mandelic acid. The positive results open up new perspectives for esterification studies with tertiary and long-chain alcohols. This work is significant in that it explores esterification reactions involving tertiary alcohols, offering a deeper understanding of the limitations and potential of these compounds in organic synthesis.