Menthol, organic compound, colorless needle-like crystals or granules. A major constituent of peppermint and spearmint essential oils, it exists in the free and ester states. Menthol has eight isomers, their aroma properties are different, levo-menthol has a minty aroma and cooling effect, the dextrorotatory menthol also has a cooling effect, the other isomers do not have a cooling effect. It can be used as the fragrance of toothpaste, perfume, beverage and candy. In medicine, it is used as stimulant, acting on the skin or mucous membranes, with cooling and itching effect; internally, it can be used for headache and inflammation of nose, throat and larynx.
Basic Information
Chinese Name
Menthol
Molecular Formula
C10H20O
Melting Point
44°C?
Boiling point
216.4°C
A terpene, also known as menthol. Molecular formula C10H20O, levo-menthol is colorless transparent menthol needle crystals; melting point 44 ° C, boiling point 216.4 ° C, specific optical rotation -48 °; slightly soluble in water, soluble in ethanol, ether, acetone, chloroform. Racemic menthol is colorless transparent needle crystals; melting point 38 ° C, boiling point 216 ° C; soluble in ethanol, ether, acetone, benzene. Menthol hydrogenation to generate p-alkanes; oxidation or catalytic dehydrogenation with chromic acid to get menthone; menthol can be split by benzoic acid esterification. Menthol can be isolated from peppermint oil, can also be manufactured from citronella aldehyde or thymol. Menthol is an important flavor. Due to its cooling effect, levo-menthol is used in large quantities in cigarettes, cosmetics, toothpaste, chewing gum, sweets and medicines, and in rubs [which act as topical itch relievers, pain relievers, coolers (mechanism: stimulates cold receptors in the skin but does not result in an actual change in temperature), and mild local anesthetics, and also acts as an osmotic stimulant]. Synthetic menthol is a mixture of various isomers and is of little value.
Menthol is made in the leaves, the main component of peppermint oil, and is a cyclic monoterpene. It is a highly volatile essential oil produced by the plant, and its constituents are mostly sesquiterpenes, monoterpenes, and sesquiterpenes, which are especially abundant in warmer climates. Some important phytochromes are terpenoids or compounds containing terpenoid groups.
Botanical origin
Peppermint Mentho haplocalyx Bing) whole herb, Moneywort Glechoma longituba (Nakai) Kupr. whole herb, Pointed perilla Perilla frutescens (L.) Britt. var .Acuto (Thunb.) Kudo leaf. ) Kudo leaves.
Molecular formula and molecular weight
C10H20O,156.27 [CAS NO.]:89-78-1
[Physical Properties]White crystals
Pharmacological Actions
It is an antipruritic, antinociceptive, antiseptic, stimulant, anesthetic, purgative, and anti-inflammatory agent that cures headache, neuralgia, itching, and inflammation of inhalation of breath mint. It can be used to treat headache, neuralgia, itching and inflammation of the respiratory tract, atrophic rhinitis, mute voice.
Take a little of the leaf powder of this product, by a small amount of sublimation of the oil, quickly add 2 drops of sulfuric acid and vanillin crystals a small amount of yellow to orange-yellow, and then add 1 drop of water, that is, it becomes purple-red. (Show menthol)
Folding editorial storage
:Airtight, avoid high temperature and strong oxidizing agents.
Menthol; menthol; [1R-(1α,2β,5α)]-5-methyl-2-(1-methylethyl)cyclohexanol; menthol ice; terpineol-[3]; p-alkan-3-ol; [1R-(1A,2B,5A)]-5-methyl-2-(1-methylethyl); 2-isopropyl-5-methylcyclohexanol; l-menthol; (-)- menthol; (-)-menthyl alcohol; (1r,3r,4s)-(-)-menthol; (1r-(1-alpha,2-beta,5-alpha))-5-methyl-2-(1-methylmenthylgas chromatographyethyl)cyclohexanol; (l)- menthol; (r)-(-)-menthol
Information: CAS:2216-51-5
Molecular formula: C10H20O
Molecular mass: 156.26
Boiling point: 212°C
Melting point: 41-43°C
Chinese name: Menthol. Menthol; [1R-(1α,2β,5α)]-5-methyl-2-(1-methylethyl)cyclohexanol; Menthol Ice; Terpineol-[3]; p-Alkan-3-ol; [1R-(1A,2B,5A)]-5-methyl-2-(1-methylethyl); 2-Isopropyl-5-methylcyclohexanol
English Name: l-menthol; (-)-menthol menthol; (-)-menthyl alcohol; (1r,3r,4s)-(-)-menthol; (1r-(1-alpha,2-beta,5-alpha))-5-methyl-2-(1-methylethyl)cyclohexanol; (l)-menthol ;(r)-(-)-menthol
Folding Editorial Properties
Colorless needle-like crystals or granules. Melting point 41-43 ° C (42-45 ° C), boiling point 216.5 ° C, relative density 0.890 (15/15 ° C), refractive index of 1.458. Soluble in alcohol; chloroform; ether; glacial acetic acid; liquid paraffin and petroleum ether, slightly soluble in water. Menthol contains three asymmetric carbon atoms, known four space cis and trans isomers, each of which has a dextrorotatory type; levorotatory type and racemic type. Levo-menthol has a characteristic minty aroma and has a cooling effect. Racemic menthol ([89-78-1]) also has a cooling effect; the other isomers do not.
Folding Editorial Production
Menthol can be purified from natural peppermint crude oil or synthesized. The aboveground parts of the labiatae plant peppermint (stems; branches; leaves and inflorescences) by steam distillation of the essential oil is called peppermint crude oil, the rate of 0.5-0.6. There are a variety of methods to synthesize the thin synthetic brain. 1. Manufacture from citronella aldehyde Using citronella aldehyde is easy to ring into the nature of isohumol, the right-handed citronella aldehyde with an acid catalyst (eg, silica gel) cyclization into the left-handed isohumol, divided out of the left-handed isohumol, hydrogenation to generate L-isohol, and hydrogenated to L-isohol. The stereoisomer can be partially converted to dextro-citronellal by thermal cracking and recycled.2. Manufacture from thymol Thymol is produced by alkylation of m-cresol in the presence of aluminum m-cresol. Catalytic hydrogenation yields all four pairs of menthol stereoisomers (i.e., racemic menthol; racemic neomenthol; racemic isomenthol and racemic neoisomenthol). The isomers were isolated and optically split by distillation, elimination of the racemic menthol fraction, and repeated recrystallization after manufacture of the esters. The isolated levo-menthol esters were saponified to obtain menthol.
Menthol is an important spice, there are a variety of production methods:
①from the manufacture of peppermint oil: the peppermint oil will be frozen after the precipitation of crystals, centrifugation of the resulting crystals with a low-boiling solvent recrystallization of pure levo-menthol. After removing the crystallization of the mother liquor still contains menthol 40% ~ 50%, also contains a large number of menthol ketone, by hydrogenation into a mixture of levo-menthol and dextro-neo-menthol. The part of the ester is saponified, and more levo-neo-menthol can be obtained by crystallizing, distilling or making its borate ester and then splitting off the other parts of the peppermint oil.
②Manufacture from citronella aldehyde:Using citronella aldehyde is easy to cyclize into isohumol nature, the dextro citronella aldehyde with an acid catalyst (such as silica gel) cyclized into levo-isohumol, split out the levo-isohumol, hydrogenated to produce levo-menthol. Its stereoisomer can be partially reconverted to dextro citronellal by thermal cracking and recycled.
③From thymol manufacture: thymol hydrogenation of all four pairs of menthol stereoisomers
Folding editorial applications
Common applications
Menthol and menthol can be used as a toothpaste, perfume, beverages and confectionery, such as aroma-enhancing agents. In medicine, they are used as stimulants, acting on the skin or mucous membranes, with cooling and itching effects; internally, they can be used for headaches and inflammation of the nose, throat and larynx. Its ester is used in spices and drugs. In the world, China and Brazil are the main producers of natural peppermint, peppermint oil production reached 2000-3000t.
"Cool sanitary napkins" and its health debate
Some sanitary napkin brands will be applied to the surface of the sanitary napkin menthol and other substances, the development of "cool sanitary napkin" varieties. The properties of these substances are utilized to create a "cool" feeling. However, it should be noted that sensitive skin and allergic women, should be careful to use added fragrances and medication components of the sanitary napkin, so as not to cause skin irritation and allergic reactions.
In response to the "cool sanitary napkin", there are rumors that it "destroys the weak acidic environment of the genitals, the destruction of the weak acidic environment will make the genitals of their own resistance to decline! If you use it, you'll get less and less menstrual flow." However, this claim is not reliable. The reasons include:
1, "cool sanitary napkin" to destroy the weak acid environment of the vagina may be theoretically valid, but in practice may be less. The balance of the micro-ecological environment of the vagina has a certain defense function against the invasion of external microorganisms, known as the self-purification effect of the vagina. Estrogen, Lactobacillus vaginalis, and the weakly acidic environment of the vagina are three important components that make up the vaginal self-purification ability. Studies on menthol have shown that menthol itself has a certain antibacterial ability, and theoretically under a certain dosage may lead to the destruction of the weakly acidic environment of the vagina. In practice, however, the concentration of menthol required to produce a cooling sensation is much lower than its minimum antibacterial concentration, and it is difficult to produce an antibacterial effect with the menthol that is applied topically and actually enters the vagina.
2, "cool tampons" will not make menstrual flow less and less. First of all, menthol does not have the pharmacological effects of sex hormones and does not affect the endocrine system, which would have no effect on menstruation. Secondly, the uterus and the vagina are two relatively isolated environments, and only during menstruation the cervical opening opens slightly in order to expel the menstrual flow from the uterine cavity. Therefore, the amount of chemicals such as menthol that can diffuse from the surface of the sanitary napkin into the uterine cavity is negligible, and is unlikely to affect the intrauterine environment.
Additionally, some so-called herbal sanitary napkins, including "cooling sanitary napkins," are advertised as having certain health and therapeutic effects on women, which should not be taken lightly. On the one hand, there is no reliable evidence that these publicized efficacy is actually effective; on the other hand, due to the dense structure of the skin, drug absorption is limited, even if it is proven effective in other areas of the drug, does not mean that the use of sanitary napkins on the same effective.
Folding Editor's Note
Because of the irritating effect on the skin and eyes and the toxicity of the product, gloves and safety glasses must be worn when using large quantities.
[Poisoning first aid]
1, inhalation: transfer the poisoned person to a ventilated place and take general first aid measures.
2. Eyes: Flush the eyes as usual, consult a physician if necessary.
3. Skin contact: Wash with water and soap.
4. Other: Consult a physician.
Regular menthol can be separated from the other three pairs of isomers by distillation, and the remaining mixture of isomers can be equilibrated under thymol hydrogenation to form regular menthol, regular neo-menthol, and regular iso-menthol in the ratio of 6:3:1, with the content of neo-iso-menthol being so small that it can be ignored. From the above mixture, racemic menthol can be separated. Racemic menthol by benzoate saturated solution or its supercooled mixture to levulinic ester inoculation crystallization, separate after saponification, get pure levulinic menthol; do not want to dextro-menthol and other isomers, can then according to the hydrogenation conditions of equilibrium transformation to racemic menthol.