Determinação de propriedades físico-químicas dos nades à base de açúcar, cloreto de colina e ácido cítrico

Abstract

Deep eutectic solvents (DESs) are known today as "green solvents," presenting attractive properties for the industry and meeting the current requirements of Green Chemistry. These solvents consist of a hydrogen bond donor (HBD) component and a hydrogen bond acceptor (HBA) component. An important class of DESs that has gained prominence is natural deep eutectic solvents (NADESs), derived from natural sources and fundamental metabolic reactions of living organisms. NADESs have some desirable characteristics, such as low toxicity, biodegradability, and low cost, which have drawn the attention of researchers for use in liquid-liquid extraction, electrochemistry, and biocatalysis. In this study, the synthesis of NADES formed by organic sugars (fructose, sucrose, and glucose), citric acid, and choline chloride was investigated. Their fundamental physicochemical properties, such as density, viscosity, and electrical conductivity, were evaluated over a temperature range between 303 – 333 K. Refractive index and pH properties were obtained at 293 K and 1 atm. These properties were also evaluated and studied for two NADESs based on fructose and citric acid with an alcohol (ethanol). The synthesis of NADES was carried out by the heating method. Temperature strongly influenced the studied physicochemical properties. The increase in the molar proportion of sugar in NADES resulted in an increase in density, viscosity, and electrical conductivity values. The pH of NADES, in general, is low (<7), with the citric acid/choline chloride mixture having the lowest value. The refractive index values of NADES varied according to the color characteristics of each sample.