Menthol

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Menthol
Menthol crystals sample.jpg
Names
IUPAC name
(1R,2S,5R)-2-Isopropyl-5-methylcyclohexanol
Other names
3-p-Menthanol
5-methyl-2-(1-methylethyl)cyclohexanol
Hexahydrothymol
Menthomenthol
Peppermint camphor
Identifiers
Jmol-3D images Image
Properties
C10H20O
Molar mass 156.27 g/mol
Density 0.890 g/cm3 (racemic or (−)-isomer)
Melting point 36–38 °C (97–100 °F; 309–311 K) racemic
42–45°C, (-)-isomer, α crystalline form
Boiling point 212 °C (414 °F; 485 K)
1.35799 g/100 ml (at 25 °C)[1]
Solubility Soluble in glacial acetic acid, chloroform, diethyl ether, anhydrous ethanol, hexane, petroleum ether
Slightly soluble in methanol
Solubility in methanol 0.1 g/100 ml
Vapor pressure 7.67x10-3 mmHg at 25 °C
Hazards
Safety data sheet ScienceLab
Flash point 93 °C
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Menthol is an organic compound, found in various plants, such as peppermint, widely used in medicine and in food industry. Menthol is available as several isomers, with the (−)-menthol enantiomer form being the most common form in nature.

Properties

Chemical

Menthol can be oxidized with chromium trioxide to menthone. Diluted sulfuric acid dehydrates menthol to 3-menthene.

Physical

Menthol is a colorless, waxy crystalline solid at room temperature, with a strong pleasant smell. It is slightly soluble in water, but more so in organic solvents. There are many different values for the water solubility in literature, mostly due to the different racemic composition, as well as traces of other organic contaminants. Is is also soluble in glacial acetic acid, chloroform, diethyl ether, anhydrous ethanol, methanol (100 mg/ml), petroleum ether.

Availability

Menthol is sold by various chemical suppliers, and is available either as racemic mixture or as individual isomers.

Menthol is also sold in various pharmacies as an alcoholic solution, as a weak local anesthetic and counterirritant.

Menthol can be extracted form various plants, such as peppermint, though you will need a large amount of plant material to obtain useful quantities of menthol.

Preparation

Synthesizing menthol is a long and costly process, and you're better off extracting it from peppermint.

Projects

  • Make beautiful large crystals
  • Make an air freshener
  • Make sodium metal

Handling

Safety

Menthol has low toxicity when inhaled, though it's best to avoid consuming large quantities of it.

Storage

Menthol should be stored in closed bottles, at temperatures lower than 35-40 °C. It can also be stored in the fridge.

Disposal

Menthol has low toxicity and can be poured down the drain, dumped in trash or poured in the soil.

References

  1. Ajisaka; Hara; Mikuni; Hashimoto; Bioscience, biotechnology, and biochemistry; vol. 64; nb. 4; (2000); p. 731 - 734

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