Phase Transfer Catalysts

CatOnium phase transfer catalysts (PTC) are quaternary ammonium and phosphonium salts, which are widely used in the production of:

Additives	Monomers
Agrochemicals	Organic fine chemicals
Dyes	Pharmaceuticals
Explosives	Petrochemicals
Flavors	Resins
Fragrances	Rubber
Monomers	Surfactants
Paint & Coatings	Zeolite templates

In addition CatOnium Phase Transfer Catalysts are also used in polymer modifications and pollution treatment and the removal or destruction of impurities in
wastes and product streams.

Typical reactions where CatOnium phase transfer catalysts are employed include:

Aldol condensation	Dehydrohalogenation	N-, C-, and S-alkylation
Borohydride reduction	Etherification	Oxidation and epoxidation
Carbene reactions	Esterification and transesterification	Reduction
Carbonylation	Hydrohalogenation	Transition metal co-catalysis
Chloromethylation	Hydrogenation	Wittig reaction
Darzens condensation	Michael addition

Displacements reactions using:

Acyl halides	Bromides	Iodides
Alkyl halides	Cyanates	Phosphoro halides
Allyl chloride	Cyanides	Thiocyanates
Anhydrides	Epichlorohydrin	Sulfides
Aryl halides	Fluorides	Sulfonyl halides
Azides	Inorganic nucleophiles

Benefits
The use of phase CatOnium phase transfer catalysts offers number of benefits from synthetic, economic, manufacturing and engineering point of view. This includes:

Easy and reliable up-scaling	Low investments costs
Elimination of expensive and dangerous reactants such as metal alkoxides	Mild reaction conditions with increased process reliability
Flexibility in solvent choice	Minimization of industrial waste
High yield and purity of the end	Reduced reaction time
Increased reaction rates that leads to enhanced selectivity	Reduction of side products output
Increased reactor volume efficiency	Reduction or even elimination of the use of organic solvents
Low energy consumption	Simplicity of the synthetic procedure

Most common CatOnium PTC’s are quaternary ammonium salts containing either alkyl or mixed alkyl/aryl groups. Their applicability is restricted by the thermal stability which is limited to about 100°C. CatOnium phase transfer catalysts comprises broad range of quaternary ammonium halides, with F^–,Cl^–,Br^– and I^– as counter anions, and limited number of quaternary hydroxyl ammonium compounds, with an OH^– group as counter anion.

Phosphonium PTC’s are used in the cases in which the use of ammonium compounds is not suitable because of their thermal instability.
The thermal stability of CatOnium quaternary phosphonium salts is quite good in a range between 120-150°C, with indications that they can be also used at temperatures up to 200 °C.