a cooling effect as a substitute for real ice in the absence of water or electricity (pouch, body patch/sleeve or cream). In various patches ranging from fever-reducing patches applied to children's foreheads to "foot patches" to relieve numerous ailments (the latter being much more frequent and elaborate in Asia, especially Japan: some varieties use "functional protrusions", or small bumps to massage one's feet as well as soothing them and cooling them down). In some beauty products such as hair conditioners, based on natural ingredients (e.g., St. ⁠Ives). As an antispasmodic and smooth muscle relaxant in upper gastrointestinal endoscopy. In organic chemistry, menthol is used as a chiral auxiliary in asymmetric synthesis. For example, sulfinate esters made from sulfinyl chlorides and menthol can be used to make enantiomerically pure sulfoxides by reaction with organolithium reagents or Grignard reagents. Menthol reacts with chiral carboxylic acids to give diastereomic menthyl esters, which are useful for chiral resolution. It can be used as a catalyst for sodium production for the amateur chemist via the alcohol catalysed magnesium reduction process. menthol is potentially ergogenic (performance enhancing) for athletic performance in hot environments Reactions Menthol reacts in many ways like a normal secondary alcohol. It is oxidised to menthone by oxidising agents such as chromic acid or dichromate, though under some conditions the oxidation can go further and break open the ring. Menthol is easily dehydrated to give mainly 3-menthene, by the action of 2% sulfuric acid. Phosphorus pentachloride (PCl5) gives menthyl chloride. History In the West, menthol was first isolated in 1771, by the German, Hieronymus David Gaubius. Early characterizations were done by Oppenheim, Beckett, Moriya, and Atkinson. It was named by F. L. Alphons Oppenheim (1833–1877) in 1861. Compendial status United States Pharmacopeia 23 Japanese Pharmacopoeia 15 Food Chemicals Codex Safety The estimated lethal dose for menthol (and peppermint oil) in humans may be as low as 50–500 mg/kg, (LD50 Acute: 3300 mg/kg [Rat]. 3400 mg/kg [Mouse]. 800 mg/kg [Cat]). Survival after doses of 8 to 9 g has been reported. Overdose effects are abdominal pain, ataxia, atrial fibrillation, bradycardia, coma, dizziness, lethargy, nausea, skin rash, tremor, vomiting, and vertigo. See also Aroma compound Carvone Chlorobutanol Ethyl benzoate Ethyl salicylate Menthoxypropanediol Methyl salicylate Menthol cigarettes Menthyl isovalerate Menthyl nicotinate p-Menthane-3,8-diol Thujone Vapor pressure References Further reading External links Ryoji Noyori Nobel lecture (2001) A review of menthol from the Science Creative Quarterly Analgesics Antipruritics