Synthesis Of Functional Ionic Liquids And Their Applications In Fisher Esterification

The esterification reaction of carboxylic acid with alcohol is one of the mostimportant and commonly employed reactions in organic and bioorganic synthesis. Thesynthesis of esters using small amount of homogeneous acid catalysts, such as sulphuricacid, hydrogen chloride, orthophosphoric acid and boric acid or metal salts supported onsolid supports are well known. But the drawbacks of these common methods arerequirement of large excess of volatile or ganic solvents (VOCs), the final neutralizationof the homogeneous acid catalyst, or separation of the metal catalyst supported on solidsupport and moreover the removal of adsorbed products from the catalyst is quite difficult.Ionic liquids (ILs) have been revealed as green reaction media and widely used in catalyticfield owing to their negligible volatility, excellent thermal stability, and the variety ofstructures available.Nine Lewis acidic ionic liquids were synthesized and characterized. The acidity andthermal stabilities of ILs were measured. Studied the synthesis of diisopropyl succinatecatalyzed by ionic liquids. It was shown that the reaction is homogeneous catalyzed byLewis acidic ionic liquids, and the separation of product is similar with the traditionalprocess. Lewis acidic ionic liquids displayed poor heat stability, but the structures werestable under the conditions of esterification reaction. The catalysts had good catalyticeffect on the reaction which we conjectured was closely related to acidity.Seven Br nsted acidic ionic liquids were synthesized and characterized. Theirthermal stabilities were characterized by TGA-DTA, and studied the synthesis of dimethylsuccinate, diethyl succinate, diisopropyl succinate catalyzed by ionic liquids. The optimalconditions for the synthesis of succinate ester were obtained. Product yield reaches orexceeds the level of reported in the literature. Moreover, the catalyst was recycled7timeswithout substantial diminution in activity.Four kinds of functional binuclear ionic liquids were designed and exploited and theirstructures were characterized by FT-IR and1H-NMR. Key physicochemical properties,such as melting point, thermal stability, acidity, corrosivity and solubility in commonsolvents were determined. The synthesized dicationic salt bis-(3-methyl-1-imidazole)butylidene double P-toluene sulfonic acid salt (Im-PTSA) tested for the esterification ofmonocarboxylic acids and dicarboxylic acids with different alcohols. The esterificationwas carried out under mild reaction conditions and without any additional organic solvent, carboxylic acids were successfully converted into esters with good yields andhigh selectivity. The produced esters were easily recovered due to immiscibility with theionic liquid as green reaction medium, the ionic liquid was recycled and reused. Thus,reported dicationic ionic liquid was a promising catalyst for esterification reaction.