miscible with both. So, the phase boundary is eliminated, reactants freely mix and react fast. But for large scale production of any product, use of a third solvent is not convenient as it may be expensive. For such problems phase transfer catalysis provides a simple solution, which avoids the use of solvents.
It directs the use a phase transfer catalyst (a phase transfer reagent) to facilitate transport of a reactant in one solvent to the other solvent where the second reactant is present. As the reactants are now brought together, they rapidly react and form the product. Example: Substitution of Cl and CN – in the following reaction. R-Cl + NaCN R-CN + N aCl organic phase aqueous phase organic phase aqueous phase R-Cl= -chlorooctane R-CN= -cyanooctane By direct heating of two phase mixture of organic -chlorooctane with aqueous sodium cyanide for several days, -cyanooctane is not obtained.
However, if a small amount of quaternary ammonium salt like tetraalkylammoniumchloride is added, a rapid transition XII U10-Surface XII U10-Surface - - - - of -cyanooctane occurs in about % yield after or hours. In this reaction, the tetraalkylammonium cation, which has hydrophobic and hydrophilic ends, transports CN from the aqueous phase to the organic phase using its hydrophilic end and facilitates the reaction with -chlorooctane as shown below: NaCN + R N Cl Na R N CN + Cl aqueous phase It moves to organic phas e R N CN + R-Cl R-CN + R N Cl Both in organic phase organic phase It moves to aqueous phase, releases Cl again pick s up CN and transports it. So phase transfer catalyst, speeds up the reaction by transporting one reactant from one phase to another. Nano Catalysis: Nano materials such a metallic nano particles, metal oxides, etc., are used as catalyst in many chemical transformation, Nanocatalysts carry the advantages of both homogeneous and heterogeneous catalyses.
Like homogeneous catalysts, the nanocatalysts give % selective transformations and excellent yield and show extremely high activity. Like the heterogeneous catalysts, nanocatalysts can be recovered and recycled. Nanocatalysts are actually soluble