Since 1971 when useful working concepts for the technique of phase-transfer catalysis (PTC) were introduced, the understanding, development, and applica­ tions of this method for conducting organic reactions has expanded exponentially. PTC has brought vast new dimensions and options to chemists and chemical engineers. From its use in less than ten commercial processes in 1975, PTC use has increased so that in the early 1990s it is involved in more than 600 industrial applications to manufacture products valued at between 10 and 20 billion U.S. dollars. PTC is widely used for simple organic reactions, steps in synthesis of pharmaceuticals, agricultural chemicals, perfumes, ftavorants, and dyes; for specialty polymerization reactions, polymer modifications, and monomer synthe­ sis; for pollution and environmental control processes; for analysis oftrace organic and inorganic compounds; and for many other applications. Often, PTC offers the best (and sometimes only) practical technique to obtain certain products. The authors experience in teaching a short course on phase-transfer catalysis has shown to us that a newcomer to PTC can easily be frustrated and confused by the large amount of information available in the literature and in patents. The purpose of this book, therefore, was to bring this information together in a logical and user-friendly way, without sacrificing matters of scholarly and fundamental importance.