Quaternary Ammonium Salts presents procedures for reducing reaction times and the need for extreme conditions, which are frequently encountered under standard reaction procedures. Quaternary ammonium compounds provide an easy solution to transfer the anionic reactants as non-solvated ion-pairs from aqueous media into organic media. The resultant effect is to increase the rate of the organic reaction by enhancing the reactivity of the anionic species and increasing the encounter rate with the organic substrate. Overall yield is increased by an elimination of side reactions. This book briefly reviews the role of quaternary ammonium compounds as phase-transfer catalysts. Various synthetic examples are provided in the text with references.