Tricresyl phosphate

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Tricresyl phosphate
Tri-o-cresyl phosphate.svg
CAS number 1330-78-5 YesY
ChemSpider 21106216 YesY
Jmol-3D images Image 1
Molecular formula C21H21O4P
Molar mass 368.37 g/mole
Appearance colourless liquid
Melting point −40 °C (−40 °F; 233 K)
Boiling point 255 °C (491 °F; 528 K) (10 mmHg)
Flash point > 225 °C (437 °F; 498 K)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Tricresyl phosphate, abbreviated TCP, is an organophosphate compound that is used as a plasticizer and diverse other applications. It is a colourless, viscous liquid, although commercial samples are typically yellow. It is virtually insoluble in water.


Tricresyl phosphate is manufactured by reaction of cresols with phosphorus oxychloride:

OPCl3 + 3 HOC6H4CH3 → OP(OC6H4CH3)3 + 3 HCl

The cresol is a mixture of three isomers (ortho, meta, and para). The fact that tricresyl phosphate is derived from a mixture and itself is a mixture ensures that it remains liquid over a wide span of temperatures.

Chemical reactions[edit]

In alkaline medium it undergoes hydrolysis to cresol and dicresyl phosphate.

OP(OC6H4CH3)3 + NaOH → + HOC6H4CH3 + NaO2P(OC6H4CH3)2

In the body, it is metabolized in part by hydroxylation to give a catecholate derivative, which is the bio-active agent responsible for the neurotoxicity.[1]


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 tetraethyllead.[2] It is a hydraulic fluid and a heat exchange medium. Exploiting its hydrophobic properties, it is used for the waterproofing of materials. It is a solvent for extractions, a solvent for nitrocellulose and other polymers. It is used as an antiwear and extreme pressure additive in lubricants and hydraulic fluids.[1][3]


TCP is the cause of numerous poisonings and is a neurotoxin, in part via organophosphate-induced delayed neuropathy.[4] It is of “toxicological importance” and has been responsible for many deaths. One of the most serious incidents occurred in the 1920s when TCP was an adulterant for Jamaica ginger.[1] Another occurred in Morocco, in 1959, when cooking oil was adulterated with jet engine lubricant containing TCP.[5]

TCP's mechanism of action is similar to other organophosphates in that it can inhibit the enzyme acetylcholinesterase, leading to a buildup of acetylcholine in the synaptic space. This can lead to hyperactivity in cholinergic neurons in the brain and at neuromuscular junctions in the peripheral nervous system resulting in apoptosis of those cell-types. This is the reason for paralysis and other irreversible neurological problems seen in the "Gingerjake" syndromes during prohibition, when TCP was added to gingerjake moonshine.[1]

TCP is used as an additive in turbine engine oil and can potentially get into the airliner cabins via a bleed air "fume event". Aerotoxic syndrome is the name given to the alleged health ill-effects caused by exposure to engine chemicals; despite UK industry-funded studies not yet making a link between TCP and any long-term health issues [6] the World Health Organisation stated in 1990 that "Because of considerable variation among individuals in sensitivity to TOCP, it is not possible to establish a safe level of exposure" and "TOCP are therefore considered major hazards to human health."[7] In 2012, Baker P., Cole T et al., researchers at the University of Washington seeking to identify safer anti-wear triaryl phosphate additives for jet engine lubricants, reported that isomers TCP present in synthetic jet engine oils do inhibit enzymes.[8]

TCP is combustible, although less so than typical organic compounds.


  1. ^ a b c d Jürgen Svara, Norbert Weferling, Thomas Hofmann "Phosphorus Compounds, Organic" in Ullmann's Encyclopedia of Industrial Chemistry 2006, Wiley-VCH: Wienheim. doi:10.1002/14356007.a19_545.pub2
  2. ^ Marvel & other solutions to the lead problem, checked 2009-06-18.
  3. ^ Solbu, K.; Thorud, S.; Hersson, M.; Ovrebø, S.; Ellingsen, G.; Lundanes, E.; Molander, P. (Aug 2007). "Determination of airborne trialkyl and triaryl organophosphates originating from hydraulic fluids by gas chromatography-mass spectrometry. Development of methodology for combined aerosol and vapor sampling". Journal of Chromatography A 1161 (1–2): 275–283. doi:10.1016/j.chroma.2007.05.087. ISSN 0021-9673. PMID 17574560.  edit
  4. ^ Lack of Delayed Neurotoxic Effect after Tri-o-cresyl Phosphate Treatment in Male Fischer 344 Rats: Biochemical, Neurobehavioral and Neuropathological Studies
  5. ^ Segalla, Spencer (2011). "The 1959 Moroccan Oil Poisoning and US Cold War Disaster Diplomacy." Journal of North African Studies. Available online at doi:10.1080/13629387.2011.610118
  6. ^ UK Parliament: Elements of healthy cabin air
  7. ^ Tricresyl Phosphate Environmental Health Criteria A110. International Programme On Chemical Safety (IPCS) WHO Geneva 1990
  8. ^ Identifying safer anti-wear triaryl phosphate additives for jet engine lubricants. Chemico-Biological Interactions. Volume 203, Issue 1, 25 March 2013, Pages 257–264