Quaternary ammonium salts play an important role in phase transfer catalysis. Phase transfer catalysis refers to a phenomenon in which a catalyst can accelerate or enable the reaction between substances that are immiscible in two different solvents (such as a liquid-liquid or solid-liquid biphasic system). During the reaction, the catalyst transfers an active species (such as a negative ion) from one phase to another, allowing it to react with the reactants. Phase transfer catalysis enables the reaction of ionic compounds with organic substances that are insoluble in water in low polarity solvents or accelerates these reactions. The catalyst facilitates the transfer of a compound that actively participates in the reaction from one phase to another, allowing it to react with the reactants.
Currently, phase transfer catalysts are widely used in various areas of organic reactions, such as carbene reactions, substitution reactions, oxidation reactions, reduction reactions, diazotization reactions, displacement reactions, alkylation reactions, acylation reactions, polymerization reactions, and even polymer modification. Additionally, phase transfer catalysis has found extensive applications in industries such as pharmaceuticals, agrochemicals, flavors, papermaking, tanning, and others, yielding remarkable economic and social benefits.
