Ultrasonically induced and enhanced Phase Transfer Catalysis

k. Hielscher
Hielscher Ultrasonics, DE

Keywords: phase transfer catalysis, high power ultrasound, emulsion reaction, sonochemistry

Summary:

The application of power ultrasound is a well-known tool to create extremely fine emulsions. In chemistry such extremely fine-size emulsions are used to enhance chemical reactions. This means that the interfacial contact area between two or more immiscible liquids becomes dramatically enlarged and provides thereby a better, more complete and/or faster course of the reaction. For phase transfer catalysis - the same as for other chemical reactions – enough kinetic energy is needed to start the reaction. This has various positive effects regarding the chemical reaction: 1. A chemical reaction that will normally not occur because of its low kinetic energy can get started by ultrasonication. 2. Chemical reactions can be accelerated by ultrasonically-assisted PTC. 3. Complete avoidance of phase transfer catalyst. 4. Raw materials can be used more efficient. 5. By-products can be reduced. 6. Replacement of cost-intensive hazardous strong base with inexpensive inorganic base. By these effects, PTC is an invaluable chemical methodology for organic synthesis from two and more immiscible reactants: PTC enables to use raw material of chemical processes more efficiently and to produce more cost-effectively. The enhancement of chemical reactions by PTC is an important tool for chemical production that can be improved by the use of ultrasound dramatically.