Tricresyl phosphate

Trikresylphosphate ( TKP, Eng. TCP ) are a group of chemical compounds, the different isomeric forms occur in several ( at least 10). You are phosphoric acid esters of cresols. As cresol may be present as ortho, meta or para -cresol, the isomers of TKP differ in the position of the methyl group (- CH3 ) on the three aromatic rings. They may be present for example as o, o, o- tricresyl phosphate, m, m, m-, tricresyl phosphate, p, p, p- tricresyl phosphate, as well as o, m, p - tricresyl phosphate.

Substances

If all three methyl groups attached to the same, also of Tri -x or x - tolylphosphat tricresyl phosphate (x = o, m, p) is spoken. As tricresyl i.e. p is meant generally an isomeric mixture of various shapes. Depending on the mixture of isomers present the physical and physiological properties of the substance are different. o- tricresyl phosphate and other isomers with ortho positions are toxic and inhibit the enzyme cholinesterase.

Production and representation

Trikresylphosphate can be obtained by reaction of cresols with phosphorus oxychloride:

In alkaline media, they are transformed by hydrolysis to cresols and Dikresylphosphaten. Example of sodium hydroxide:

Use

Trikresylphosphate were used as flame retardants and as plasticizers for PVC, nitro cellulose, acrylates, varnish. In addition, they served as an additive in lubricants, hydraulic fluids and other industrial oils, as well as a gasoline additive (as Antipräignitionsstoff, so Rückstandsumwandler ). However, they are currently to no longer used because of their toxicity. An exception to this is the use as an additive for oils (up to 5 % share) for aircraft engines, where they are still in use today, what with dealing with just such disorders and constitutes a danger to the environment, the crew and passengers.

Other applications include the use of Trikresylphosphaten as refrigerants, solvents, an intermediate in chemical syntheses and absorbent ( washing liquid, such as phenol).

Safety

The o, o, o- isomer - and thus the isomer mixture - is a neurotoxin ( neurotoxic ), it inhibits the enzyme acetylcholinesterase ( cholinesterase inhibitor ). In case of poisoning with these substances health problems are frequently observed. On the one hand, characteristically delayed, vomiting, abdominal pain and diarrhea, and on the other hand long-term neurological symptoms such as paralysis, dizziness, headache, fatigue, palpitations, shortness of breath, joint and muscle pain. For passengers, flight attendants and pilots poisoning cases are known, which are deemed by poisoning with CPM, since the bleed air from aircraft in case of accidents may be contaminated with CPM.