biology

Tricresyl phosphate

Tricresyl phosphate is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Tricresyl phosphate rather than just read about it. In short: Tricresyl phosphate (TCP) is a mixture of organophosphate compounds most notably used as a flame retardant. Other uses include as a plasticizer in manufacturing for lacquers and varnishes and vinyl plastics and as an antiwear additive in lubricants.

Key takeaways

Tricresyl phosphate belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Tricresyl phosphate to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Tricresyl phosphate from memory before moving on to harder problems.

Reference excerpt

Tricresyl phosphate (TCP) is a mixture of organophosphate compounds most notably used as a flame retardant. Other uses include as a plasticizer in manufacturing for lacquers and varnishes and vinyl plastics and as an antiwear additive in lubricants. Pure tricresyl phosphate is a colourless, viscous liquid, although commercial samples are typically yellow. It is virtually insoluble in water, but easily soluble in organic solvents like toluene, hexane, and diethyl ether among others. It was synthesized by Alexander Williamson in 1854 upon reacting phosphorus pentachloride with cresol (a mixture of para-, ortho-, and meta- isomers of methylphenol), though today's manufacturers can prepare TCP by mixing cresol with phosphorus oxychloride or phosphoric acid as well. The ortho isomer of TCP is a rather toxic substance with a long history of causing mass poisonings.

Isomers Many isomers of tricresyl phosphate exist and comprise typical samples of this compound. The World Health Organization 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." The most toxic isomer is tri-ortho-cresyl phosphate, (TOCP). Strenuous efforts have been made to minimize the content of the ortho isomers in commercial TCP if there is a risk of human exposure. However other isomers present in synthetic jet engine oils do inhibit certain enzymes.

Toxicity TCP has very low acute toxicity, but it is transformed in the body to a highly toxic metabolite. In humans, the first symptoms are weakness/paralysis of the hands and feet on both sides of the body due to damage to the peripheral nervous system (polyneuropathy) and a sensation of pins-and-needles (paresthesia). Onset typically occurs between 3–28 days from initial exposure. If ingested, this can be preceded by gastrointestinal symptoms that include nausea, vomiting, and diarrhea. Rates of metabolism vary by species and by individual; some people developed severe polyneuropathy after ingesting 0.15g of TOCP, whereas others have been reported asymptomatic after 1-2g. Though death is uncommon in acute exposure cases, the result of paralysis can last for months or years due to differences in gender, age, and route of exposure. The cardinal treatment is physical therapy to restore the use of the hands and feet, though it can take up to 4 years to only regain a fraction of motor control. Exposure to TOCP has been characterized by a list of observations:

Cholinesterase levels will remain unchanged or show no significant changes. Electromyography will show partial or complete reactions of degeneration. An increase of protein in cerebrospinal fluid. Swelling of the parotid glands (non-tender).

Metabolism

Although TOCP is mainly excreted through urine and feces, it is partially metabolized by the hepatic cytochrome P450 system. Pathways include hydroxylation at one or more methyl groups, dearylation (removal of a o-cresyl group) and conversion of the hydroxymethyl groups to an aldehyde or a carboxylic acid. Human metabolism results in a saligenin cyclic o-tolyl phosphate (SCOTP) metabolite, an known enzyme inhibitor. This metabolite is able to inhibit neuropathy target esterase (NTE) and results in the classic organophosphate-induced delayed neuropathy (OPIDN). In tandem, TOCP exerts physical damage by causing axonal destruction and myelin disintegration within specialized cells that transmit nerve impulses (neurons). In addition to the formation of SCOTP, the interactions between TOCP and two different human cytochrome P450 complexes (1A2 and 3A4) can further produce 2-(ortho-cresyl)-4H-1,2,3-benzodioxaphosphoran-2-one (CBDP). This metabolite can bind to butyrylcholinesterase (BuChE) and/or acetylcholinesterase (AChE). Binding to BuChE results in no adverse effects, for its typical role is to covalently bind to organophosphate poisons and detoxify them by inactivation. The dangers in metabolizing TOCP to CBDP occur when its potential to bind to AChE become imminent, for inactivation of the enzyme in nerve synapses can be lethal. The enzyme plays a tantamount role in terminating nerve impulse transmission "by hydrolyzing the neurotransmitter acetylcholine." Upon inactivation, acetylcholine can no longer be broken down in the body and results in uncontrollable muscle spasms, paralyzed breathing (bradycardia), convulsions, and/or death. Luckily, TOCP is considered a weak AChE inhibitor.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Tricresyl phosphate

Start with the simplest possible case. Write down what Tricresyl phosphate claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Tricresyl phosphate before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Tricresyl phosphate ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Tricresyl phosphate

In research: Tricresyl phosphate appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Tricresyl phosphate in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Tricresyl phosphate is common in secondary-school and first-year university syllabi. It links to neighbouring topics Acetylcholinesterase inhibitors, Ester solvents, Flame retardants, so understanding it makes those chapters shorter.
In everyday life: Look for Tricresyl phosphate outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Tricresyl phosphate in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Tricresyl phosphate means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Tricresyl phosphate out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Tricresyl phosphate in simple terms?

Why does Tricresyl phosphate matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Tricresyl phosphate?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Tricresyl phosphate.