Phase transfer catalysis (PTC) uses catalytic amounts of phase transfe
r agents which facilitate interphase transfer of species, making react
ions between reagents in two immiscible phases possible. PTC is used w
idely in the synthesis of various organic chemicals in both liquid-liq
uid and solid-liquid systems. Existing literature on PTC is chemistry-
intensive and a mere handful of recent articles constitute the entire
information on engineering analysis. This article reviews the field co
mprehensively by combining the existing knowledge from chemistry with
insights into mechanistic and kinetic analysis and mathematical modeli
ng of soluble and insoluble PTC. By its very nature, PTC involves a se
ries of equilibrium and mass-transfer steps, beside the two main react
ions. Neglect of mass-transfer effects can grossly overpredict the con
version of a PTC mediated reaction. A practical way of using PTC, whic
h enables easy separation is to immobilize the catalyst on a solid sup
port. Mass-transfer limitations and higher costs, however have preclud
ed its commercial use so far, requiring further analysis of mass-trans
fer limitations in these complex three-phase systems. The use of PTC,
combined with other rate enhancement techniques like sonochemistry, mi
crowaves, electroorganic synthesis, and photochemistry, is being incre
asingly explored. Applications in this area in the manufacture of orga
nic intermediates and fine chemicals seem almost unlimited.