Tricresyl phosphate

Overview
Tricresyl phosphate, abbreviated TCP, is an organophosphate compound. It is a derived from cresol and phosphoric acid. This viscous liquid is colourless when pure, but commercial samples are typically yellow. It is nonflammable and virtually insoluble in water. Commercial tricresyl phosphate is a mixture of ortho, meta, and para-cresyl phosphates, the m- isomer is , the p- isomer is , and the o- isomer is.

Production
Tricresyl phosphate is manufactured by reaction of cresols with phosphorus oxychloride:
 * OPCl3 +  3 HOC6H4CH3   →  OP(OC6H4CH3)3  +  3 HCl

In alkaline medium it undergoes hydrolysis to cresol and dicresyl phosphate.
 * OP(OC6H4CH3)3 +  NaOH  →    +  HOC6H4CH3  +  NaO2P(OC6H4CH3)2

Uses
Tricresyl phosphate is used as a plasticizer in nitrocellulose, acrylate lacquers, varnishes, and in polyvinyl chloride. It is a flame retardant in plastics and rubbers. It is used as a gasoline additive as a lead scavenger for tetra-ethyl lead. It is a hydraulic fluid and a heat exchange medium. Exploiting its hydrophobic properties, it is used in waterproofing of materials. It is a solvent for extractions, a solvent for nitrocellulose and other polymers. It is also used as an AW additive and EP additive in lubricants, and in hydraulic fluids. As a gasoline additive, it also helps preventing engine misfires.

Safety
TCP is a known neurotoxin and is of “toxicological importance” and has been responsible for many deaths. The most serious incident arose in the 1920s when TCP was used as an adulterant for Jamaican ginger.

Aircraft
TCP is found in the engine oil of commercial jet airliners. It has been suggested that it can contaminate the cabin air through the engine bleed air system, and could therefore cause negative health effects in crew and passengers. Tests have found raised levels of TCP in some airline cabins, although the link between cabin TCP contamination and ill health, or conditions such as Jet lag, has yet to be proved, although has been suggested.