Phase Transfer Catalysts (PTCs) are catalysts that enable chemical reactions between two immiscible phases, such as an aqueous and organic phase. PTCs work by transferring ions or polar molecules from one phase to the other, allowing reactions that would not occur otherwise. They are widely used in organic synthesis, including nucleophilic substitution, oxidation, reduction, and polymerization reactions. PTCs offer several advantages over traditional homogeneous catalysts, including improved selectivity, faster reaction rates, and milder reaction conditions.