Tricresyl phosphate

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Tricresyl phosphate
Names
Other names
tricresylphosphate, tri-o-cresyl phosphate, TOCP, tritolyl phosphate, tolyl phosphate, tri-o-tolyl ester of phosphoric acid
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.014.136 Edit this at Wikidata
  • InChI=1S/C21H21O4P/c1-16-10-4-7-13-19(16)23-26(22,24-20-14-8-5-11-17(20)2)25-21-15-9-6-12-18(21)3/h4-15H,1-3H3 checkY
    Key: YSMRWXYRXBRSND-UHFFFAOYSA-N checkY
  • InChI=1/C21H21O4P/c1-16-10-4-7-13-19(16)23-26(22,24-20-14-8-5-11-17(20)2)25-21-15-9-6-12-18(21)3/h4-15H,1-3H3
    Key: YSMRWXYRXBRSND-UHFFFAOYAP
  • Cc3ccccc3OP(=O)(Oc1ccccc1C)Oc2ccccc2C
Properties
C21H21O4P
Molar mass 368.37 g/mole
Appearance colourless liquid
Melting point -40 °C
Boiling point 255 °C (10mm Hg)
Hazards
Flash point > 225 °C
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

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.

Production

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

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]

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 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]

Safety

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.

References

  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. ^ Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1016/j.chroma.2007.05.087, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi=10.1016/j.chroma.2007.05.087 instead.
  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
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