Menthol

=Menthol (also called Peppermint Camphor or Mint Camphor)= By: Alexa

Menthol Formula: C10H20O Molar Mass: 156.27 g/mol Melting point: 87.8°F (31°C) Boiling point: 413.6°F (212°C) Density: 0.990 g cm −3 Vapor Pressure: 0.0637 mm Hg at 25°C



History of Menthol
The major compound of peppermint is menthol, it was originally from the mint plant family. It is an alcohol obtained by distilling the flowers, leaves, and roots of many plants with water. It can be from natural or synthetic sources (I-Menthol), or racemic (di-Menthol). Much of the menthol used today is synthetically made. Menthol is responsible for the taste and odor of peppermint oil, as well as the "cooling sensation" when applied to the skin and mucosal surfaces. The United States Pharmacopoeia describes menthol as forming colorless, prismatic crystals that have a strong and pure odor of peppermint and a warm aromatic taste followed by the sensation of cold when air is drawn into the mouth. On the cooling of peppermint oil the separation of menthol occurs especially if a few crystals of menthol are added to start crystallization.

Egyptian, Greeks and ancient Asian cultures were the first to discover the use of peppermint for cooking. This form of menthol, in peppermint, showed up in America during the early 19th century. Treating nausea, toothaches and other pains, it soon became very popular. In 1818, the carbon to hydrogen ratio in turpentine, a class of organic compounds that are most abundant component of essential oils, was found to be 5:8. The same carbon to hydrogen ratio was soon found in a wide variety of natural products. These products became known as terpenes. The similarities in the atomic composition of this family led to the idea that they might possess some unifying structural element. Soon, a German chemist named Otto Wallach pointed out the common structural feature of the terpenes, consisting of repeating units that have the same carbon skeletons.

In the beginning of the 20th century, an effort was made to determine the chemical constituents of essential oil. Soon, menthol materialized in cigarettes. Sold as luxury products to women, they were called "novelty cigarettes". They were mainly sold to a female market. Concerns about the use of menthol in cigarettes and whether or not it was a good idea arose.

Today, cigarettes still contain menthol, but menthol also works as a decongestant and expectorant. It's included in oral medications, mouthwashes, cough drops and cold sore medications. It can also be found in some cosmetics and candies. 75% of the world's supply of peppermint comes from the United States with Oregon being the leading mint producer. As of 1996, 31,000 acres of peppermint were growing in the United States; 3,007,000 pounds were harvested, making $35,783,000 in total.

The most important determination to be made in examining the isolated peppermint oil is that of the total amount of menthol isolated. The cost of menthol extracted from a plant's own oils is much higher than menthol synthnesized from petroleum products.

Chemical Properties
In many ways, Menthol reacts like any normal secondary alcohol. It is oxidized to menthone with oxidizing agents such as chromic acid, though some conditions of the oxidation may continue and break open the ring. Menthol is easily dehydrated to give 3-menthene by the action of 2% sulfuric acid. PCl 5  gives menthyl chloride.