Thymol

Key takeaways

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

Reference excerpt

Thymol (also known as 2-isopropyl-5-methylphenol, IPMP), C10H14O, is a monoterpenoid, phenol derivative of p-cymene, isomeric with carvacrol. It occurs naturally in oil of thyme and is extracted from Thymus vulgaris (common thyme), ajwain, and various other plants, as a white crystalline substance with a pleasant aromatic odor. Thymol provides the distinctive flavor of the culinary herb thyme, also produced from T. vulgaris. Thymol is only slightly soluble in water at neutral pH, but due to deprotonation of the phenol, it is highly soluble in alcohols, other organic solvents, and strongly alkaline aqueous solutions.

Chemical synthesis Thymol is produced by the alkylation of m-cresol with propene. CH3C6H4OH + CH2CHCH3 → ((CH3)2CH)CH3C6H3OH A predicted method of biosynthesis of thymol in thyme and oregano begins with the cyclization of geranyl diphosphate by TvTPS2 to γ-terpinene. Oxidation by a cytochrome P450 in the CYP71D subfamily creates a dienol intermediate, which is then converted into a ketone by short-chain dehydrogenase. Lastly, keto-enol tautomerization gives thymol. Its dissociation constant (pKa) is 10.59±0.10. Thymol absorbs maximum UV radiation at 274 nm.

History The bee balms Monarda fistulosa and Monarda didyma, North American wildflowers, are natural sources of thymol. The Blackfoot Native Americans recognized these plants' strong antiseptic action and used poultices of the plants for skin infections and minor wounds. A tisane made from them was also used to treat mouth and throat infections caused by dental caries and gingivitis. Thymol was first isolated by German chemist Caspar Neumann in 1719. In 1853, French chemist Alexandre Lallemand (1816-1886) named thymol and determined its empirical formula. Possible antiseptic properties of thymol were discovered in 1875, and it was first synthesized by Swedish chemist Oskar Widman (1852-1930) in 1882.

Extraction The conventional method of extracting is hydro-distillation (HD), but can also be extracted with solvent-free microwave extraction (SFME). In 30 minutes, SFME yields similar amounts of thymol with more oxygenated compounds than 4.5 hours of hydro-distillation at atmospheric pressures without the need for solvent.

Uses During the 1910s, thymol was used for hookworm infection in the United States. People of the Middle East continue to use za'atar, a delicacy made with large amounts of thyme, to reduce and eliminate internal parasites. It is also used as a preservative in halothane, an anaesthetic, and as an antiseptic in mouthwash. When used to reduce plaque and gingivitis, thymol has been found to be more effective when used in combination with chlorhexidine than when used purely by itself. Thymol is a fragrance ingredient in some cosmetics. Thymol has been used to successfully control varroa mites and prevent fermentation and the growth of mold in bee colonies. Thymol is also used as a rapidly degrading, non-persisting pesticide, such as insecticides and fungicides which are leveraged in plant care products. Thymol can also be used as a medical disinfectant and general purpose disinfectant. Thymol is also used in the production of menthol through the hydrogenation of the aromatic ring. Thymol is commonly used as a starting material in the total synthesis of thymoquinone, a quinone derivative, through catalytic oxidation.

List of plants that contain thymol

Toxicology and environmental impacts

In 2009, the U.S. Environmental Protection Agency (EPA) reviewed the research literature on the toxicology and environmental impact of thymol and concluded that "thymol has minimal potential toxicity and poses minimal risk".

Environmental breakdown and use as a pesticide Studies have shown that hydrocarbon monoterpenes and thymol in particular degrade rapidly (DT50 16 days in water, 5 days in soil) in the environment and are, thus, low risks because of rapid dissipation and low bound residues, supporting the use of thymol as a pesticide agent that offers a safe alternative to other more persistent chemical pesticides that can be dispersed in runoff and produce subsequent contamination. Though, there has been recent research into sustained released systems for botanically derived pesticides, such as using natural polysaccharides which would be biodegradable and biocompatible.

Compendial status British Pharmacopoeia Japanese Pharmacopoeia

See also Thymoquinone Nigella sativa Bromothymol

Notes and references

External links Media related to Thymol at Wikimedia Commons

Illustrations

Worked examples

Example 1 — a first encounter with Thymol

Start with the simplest possible case. Write down what Thymol claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, 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 Thymol 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 Thymol 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 Thymol

In research: Thymol appears in chemistry 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 Thymol 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: Thymol is common in secondary-school and first-year university syllabi. It links to neighbouring topics Alkylphenols, Disinfectants, Flavors, so understanding it makes those chapters shorter.
In everyday life: Look for Thymol 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.

How to study Thymol in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Thymol 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 Thymol out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Thymol in simple terms?

Thymol (also known as 2-isopropyl-5-methylphenol, IPMP), C10H14O, is a monoterpenoid, phenol derivative of p-cymene, isomeric with carvacrol. It occurs naturally in oil of thyme and is extracted from Thymus vulgaris (common thyme), ajwain, and various other plants, as a white crystalline substance…

Why does Thymol matter?

Because it connects several chemistry 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 Thymol?

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 Thymol.