Camphor

OVERVIEW

Camphor (KAM-for) is also known as gum camphor; 2-camphanone; 1,7,7-trimethylbicyclo[2.2.1]heptan-2-one; and 1,7,7-trimethylbicyclo[2.2.1]-2-heptanone, among others. It is a volatile white waxy substance with a strong, characteristic odor and a bitter, cooling taste. Its odor has been described as fragrant, aromatic, pungent, or penetrating, similar to that of mothballs. The compound is obtained from the camphor tree, Cinnamomum camphora, which is native to many parts of the world, including the Indonesian islands of Java and Sumatra, as well as China, Taiwan, Japan, and Brazil.

KEY FACTS

OTHER NAMES:

Gum camphor; also see Overview.

FORMULA:

C₁₀H₁₆O

ELEMENTS:

Carbon, hydrogen, oxygen

COMPOUND TYPE:

Cyclic ketone (organic)

STATE:

Solid

MOLECULAR WEIGHT:

152.23 g/mol

MELTING POINT:

178.3°C to 178.8°C (352.9°F to 353.4°F); varies depending on isomer

BOILING POINT:

207.4°C (405.3°F; depends on isomer); some forms sublime before boiling

SOLUBILITY:

Insoluble in water; soluble in alcohol, ether, acetone, benzene, and other organic solvents

The first mention of camphor by a Westerner occurs in the writings of the Venetian explorer Marco Polo (1254–1324) in the late thirteenth century. The Chinese had apparently been using camphor for many centuries in the embalming of their dead and the manufacture of soap, among other applications. The Japanese also had a long history of using the compound in the preparation of varnish and ink, to dilute paint, to burn for light, and to protect clothing from moths. Camphor was also used throughout Asia as a medicine to treat a wide variety of ailments, from upset stomach to rheumatism.

HOW IT IS MADE

Camphor can be obtained from every part of the Cinnamomum camphora tree, including the trunk, branches, roots, and leaves. The compound is extracted from tree parts by steam distillation and crystallization of the camphor. The camphor thus obtained is one of two possible isomers, the dextrorotary (or "+") form of the compound. (The other isomer is the levorotatory or "−" form.) Since the natural sources of camphor are inadequate to meet commercial demand, camphor is also made synthetically. The process begins by converting the straight-chain hydrocarbons in turpentine oil (C₁₀H₁₆) to a cyclic isomer, a-pinene (c-C₁₀H₁₆), which is then oxidized to make camphor. Synthetic camphor differs from natural camphor in that it consists of both isomers of the compound, the dextrorotary (+) and levorotatory (−) forms. This difference has no effect on the chemical properties of camphor, although it has some modest effect on its biological properties.

Interesting Facts

Despite its name, the camphor tree, Cinnamomum camphora, does not produce cinnamon. That compound comes from a related member of the family, Cinnamomum zeylanicum.

COMMON USES AND POTENTIAL HAZARDS

Camphor has a long history of medicinal use. People have used it as a liniment to treat muscle aches and arthritis; as a topical anesthetic; as a treatment for nervousness and hysteria; to treat diarrhea, bronchitis, and infectious fevers; and even as an injection to cure heart failure. Very little medical evidence exists for most of these treatments. As a result, its primary medicinal use today is in lotions and ointments for the relief of mild pain and discomfort due to arthritis, rheumatism, and sore muscles. Some common products that contain camphor are Absorbine Arthritic Pain Lotion®,Ben-Gay®,Campho-phenique®, Panalgesic®,Sloan's Liniment®, and Vicks VapoRub®. In these preparations, the compound acts as both a mild analgesic (pain-reliever) and antiseptic (an agent to prevent the growth of disease-causing microorganisms). Its pronounced odor may also help open nasal passages. Camphor is also an important ingredient in some antipruritic agents, substances used to relieve the discomfort of itching.

Although camphor is probably best known to most people because of its medicinal uses, the compound also has a number of important industrial applications. For example, it is added to cellulose nitrate as a plasticizer, a substance added to plastic to make it softer and more flexible. Other uses for camphor include:

• As a moth and mildew repellent in mothballs and moth flakes;
• In the embalming of dead bodies;
• In the manufacture of fireworks and explosives;
• As a preservative in pharmaceuticals and cosmetics;
• In the production of lacquers and varnishes; and
• As a chemical intermediary in the production of a number of organic compounds.

Words to Know

ANALGESIC

A substance the relieves pain.

DISTILLATION

A process of separating two or more substances by boiling the mixture of which they are composed and condensing the vapors produced at different temperatures.

ISOMERS

Two or more forms of a chemical compound with the same molecular formula, but different structural formulas and different chemical and physical properties.

One of camphor's most serious disadvantages as a medicinal product is that it is poisonous. Drinking straight camphorated oil can kill a person. In smaller doses, it can cause mental confusion, irritability, jerky movements of the arms and legs, neuromuscular hyperactivity, and seizures. Symptoms can appear between five and ninety minutes after swallowing the camphor. In 1980, the United States Food and Drug Administration limited the amount of camphor allowed in consumer products to 11 percent. It also banned products that contain concentrated camphor, such as camphorated oil and camphorated liniment.

FOR FURTHER INFORMATION

"Camphor." http://www.innvista.com/health/herbs/camphor.htm (accessed on September 29, 2005).

"Camphor." Botanical.com. http://www.botanical.com/botanical/mgmh/c/campho13.html (accessed on September 29, 2005).

"Camphor; Gum Camphor; Laurel Camphor. Camphora Officinarum." Drugstore Museum. http://www.drugstoremuseum.com/sections/level_info2.php?level_id=71&level=2 (accessed on September 29, 2005).

See AlsoCellulose Nitrate