Tricresyl phosphate
Encyclopedia
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.
s with phosphorus oxychloride:
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.
to cresol and dicresyl phosphate.
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.
in nitrocellulose
, acrylate
lacquer
s, varnish
es, and in polyvinyl chloride
. It is a flame retardant
in plastic
s and rubber
s. 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 for the 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 lubricant
s, and in hydraulic fluid
s.
, in part via organophosphate-induced delayed neuropathy
. 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 used as an adulterant
for Jamaica Ginger. Another occurred in Morocco, in 1959, when cooking oil was adulterated with jet engine lubricant containing TCP.
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.
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; UK industry-funded studies are yet to make a link between TCP and any long-term health issues.
TCP is combustible, although less so than typical organic compound
s.
Organophosphate
An organophosphate is the general name for esters of phosphoric acid. Phosphates are probably the most pervasive organophosphorus compounds. Many of the most important biochemicals are organophosphates, including DNA and RNA as well as many cofactors that are essential for life...
compound that is used as a plasticizer
Plasticizer
Plasticizers or dispersants are additives that increase the plasticity or fluidity of the material to which they are added; these include plastics, cement, concrete, wallboard, and clay. Although the same compounds are often used for both plastics and concretes the desired effects and results are...
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 cresolCresol
Cresols are organic compounds which are methylphenols. They are a widely occurring natural and manufactured group of aromatic organic compounds which are categorized as phenols . Depending on the temperature, cresols can be solid or liquid because they have melting points not far from room...
s 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 hydrolysisHydrolysis
Hydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...
to cresol and dicresyl phosphate.
- OP(OC6H4CH3)3 + NaOH → + HOC6H4CH3 + NaO2P(OC6H4CH3)2
In the body, it is metabolized in part by hydroxylation
Hydroxylation
Hydroxylation is a chemical process that introduces a hydroxyl group into an organic compound. In biochemistry, hydroxylation reactions are often facilitated by enzymes called hydroxylases. Hydroxylation is the first step in the oxidative degradation of organic compounds in air...
to give a catecholate derivative, which is the bio-active agent responsible for the neurotoxicity.
Uses
Tricresyl phosphate is used as a plasticizerPlasticizer
Plasticizers or dispersants are additives that increase the plasticity or fluidity of the material to which they are added; these include plastics, cement, concrete, wallboard, and clay. Although the same compounds are often used for both plastics and concretes the desired effects and results are...
in nitrocellulose
Nitrocellulose
Nitrocellulose is a highly flammable compound formed by nitrating cellulose through exposure to nitric acid or another powerful nitrating agent. When used as a propellant or low-order explosive, it is also known as guncotton...
, acrylate
Acrylate
The acrylate ion is the ion of acrylic acid.Acrylates are the salts and esters of acrylic acid. They are also known as propenoates ....
lacquer
Lacquer
In a general sense, lacquer is a somewhat imprecise term for a clear or coloured varnish that dries by solvent evaporation and often a curing process as well that produces a hard, durable finish, in any sheen level from ultra matte to high gloss and that can be further polished as required...
s, varnish
Varnish
Varnish is a transparent, hard, protective finish or film primarily used in wood finishing but also for other materials. Varnish is traditionally a combination of a drying oil, a resin, and a thinner or solvent. Varnish finishes are usually glossy but may be designed to produce satin or semi-gloss...
es, and in polyvinyl chloride
Polyvinyl chloride
Polyvinyl chloride, commonly abbreviated PVC, is a thermoplastic polymer. It is a vinyl polymer constructed of repeating vinyl groups having one hydrogen replaced by chloride. Polyvinyl chloride is the third most widely produced plastic, after polyethylene and polypropylene. PVC is widely used in...
. It is a flame retardant
Flame retardant
Flame retardants are chemicals used in thermoplastics, thermosets, textiles and coatings that inhibit or resist the spread of fire. These can be separated into several different classes of chemicals:...
in plastic
Plastic
A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...
s and rubber
Rubber
Natural rubber, also called India rubber or caoutchouc, is an elastomer that was originally derived from latex, a milky colloid produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored latex sap collected and refined...
s. It is used as a gasoline additive
Gasoline additive
Gasoline additives increase gasoline's octane rating or act as corrosion inhibitors or lubricants, thus allowing the use of higher compression ratios for greater efficiency and power, however some carry heavy environmental risks...
as a lead scavenger for tetra-ethyl lead
Tetra-ethyl lead
Tetraethyllead , abbreviated TEL, is an organolead compound with the formula 4Pb. An inexpensive additive, its addition to gasoline from the 1920's allowed octane ratings and thus engine compression to be boosted significantly, increasing power and fuel economy...
. It is a hydraulic fluid
Hydraulic fluid
Hydraulic fluids, also called hydraulic liquids, are the medium by which power is transferred in hydraulic machinery. Common hydraulic fluids are based on mineral oil or water...
and a heat exchange medium
Coolant
A coolant is a fluid which flows through a device to prevent its overheating, transferring the heat produced by the device to other devices that use or dissipate it. An ideal coolant has high thermal capacity, low viscosity, is low-cost, non-toxic, and chemically inert, neither causing nor...
. Exploiting its hydrophobic properties, it is used for the waterproofing
Waterproofing
Waterproof or water-resistant describes objects relatively unaffected by water or resisting the ingress of water under specified conditions. Such items may be used in wet environments or under water to specified depths...
of materials. It is a solvent
Solvent
A solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...
for extractions, a solvent for nitrocellulose and other polymers. It is also used as an AW additive
AW additive
AW additives, or antiwear additives, are additives for lubricants to prevent metal-to-metal contact between parts of gears.EP additives are usually used in applications such as gearboxes, while AW additives are used with lighter loads such as bushings....
and EP additive
EP additive
Extreme pressure additives, or EP additives, are additives for lubricants with a role to decrease wear of the parts of the gears exposed to very high pressures...
in lubricant
Lubricant
A lubricant is a substance introduced to reduce friction between moving surfaces. It may also have the function of transporting foreign particles and of distributing heat...
s, and in hydraulic fluid
Hydraulic fluid
Hydraulic fluids, also called hydraulic liquids, are the medium by which power is transferred in hydraulic machinery. Common hydraulic fluids are based on mineral oil or water...
s.
Safety
TCP is the cause of numerous poisonings and is a neurotoxinNeurotoxin
A neurotoxin is a toxin that acts specifically on nerve cells , usually by interacting with membrane proteins such as ion channels. Some sources are more general, and define the effect of neurotoxins as occurring at nerve tissue...
, in part via organophosphate-induced delayed neuropathy
Organophosphate-induced delayed neuropathy
Organophosphate-induced delayed neuropathy , also called organophosphate-induced delayed polyneuropathy , is a neuropathy caused by killing of neurons in the central nervous system, especially in the spinal cord, as a result of acute or chronic organophosphate poisoning.A striking example of OPIDN...
. 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 used as an adulterant
Adulterant
An adulterant is a chemical substance which should not be contained within other substances for legal or other reasons. Adulterants may be intentionally added to more expensive substances to increase visible quantities and reduce manufacturing costs or for some other deceptive or malicious purpose...
for Jamaica Ginger. Another occurred in Morocco, in 1959, when cooking oil was adulterated with jet engine lubricant containing TCP.
TCP's mechanism of action is similar to other organophosphates in that it can inhibit the enzyme acetylcholinesterase
Acetylcholinesterase
"Acetylcholinesterase, also known as AChE or acetylcholine acetylhydrolase, is an enzyme that degrades the neurotransmitter acetylcholine, producing choline and an acetate group. It is mainly found at neuromuscular junctions and cholinergic nervous system, where its activity serves to terminate...
, leading to a buildup of acetylcholine
Acetylcholine
The chemical compound acetylcholine is a neurotransmitter in both the peripheral nervous system and central nervous system in many organisms including humans...
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
Apoptosis
Apoptosis is the process of programmed cell death that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation...
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.
TCP is used as an additive in turbine engine oil and can potentially get into the airliner cabins via a bleed air
Bleed air
Bleed air in gas turbine engines is compressed air taken from within the engine, after the compressor stage and before the fuel is injected in the burners. While in theory bleed air could be drawn in any gas turbine engine, its usage is generally restricted to jet engines used in aircraft...
"fume event". Aerotoxic syndrome
Aerotoxic syndrome
Aerotoxic syndrome is a term describing the alleged short-term and long-term ill-health effects that are attributed to exposure to cabin air that has been contaminated with atomized engine oils and other chemicals. The documentary film Welcome Aboard Toxic Airlines suggests the term was first...
is the name given to the alleged health ill-effects caused by exposure to engine chemicals; UK industry-funded studies are yet to make a link between TCP and any long-term health issues.
TCP is combustible, although less so than typical organic compound
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...
s.