Camphor, Terpenoid, Bornanone, Camphanone, Gum Camphor, Laurel Camphor, 76-22-2

Camphor, Terpenoid, Bornanone, Camphanone, Gum Camphor, Laurel Camphor, 76-22-2

Camphor Monograph

1. General Information and Identification

Camphor is a waxy, white or transparent solid with a strong, characteristic aromatic odor. It is a terpenoid with a bicyclic structure and is classified as a ketone. Historically derived from the wood of the camphor tree (Cinnamomum camphora), it is now predominantly produced synthetically on an industrial scale.

• IUPAC Name: 1,7,7-Trimethylbicyclo[2.2.1]heptan-2-one

• Common Names:

  • 2-Bornanone

  • 2-Camphanone

  • DL-Camphor (racemic mixture)

  • Gum Camphor

  • Japan Camphor

  • Laurel Camphor

• CAS Number: 76-22-2

• Molecular Formula: C₁₀H₁₆O

• Molecular Weight: 152.23 g/mol

2. Chemical Classification and Structure

• Chemical Class: Terpenoid (Monoterpenoid)

• Sub-class: Bicyclic Monoterpene

• Functional Group: Ketone

Camphor's structure is based on a bornane skeleton, a bicyclic [2.2.1] system with two bridgehead carbon atoms. A defining feature is an oxo group (C=O) at the second carbon position, which classifies it as a ketone. This specific bridged-ring structure imparts its high volatility, ability to sublime, and its lipophilic nature, allowing it to easily penetrate biological membranes.

3. Physical and Chemical Properties

• Appearance: Colorless or white crystals, crystalline powder, or in compressed blocks. It has a characteristic, brittle texture.

• Odor: Pungent, aromatic, and penetrating. It is often described as smelling like mothballs (naphthalene) but with a more refreshing, medicinal quality.

• Taste: Sharp, burning, and cooling (similar to menthol).

• Melting Point: 174-179 °C (for the racemic mixture); pure enantiomers melt at a higher point (~180 °C).

• Boiling Point: 204 °C.

• Sublimation: A key property of camphor is its ability to sublime (transition directly from solid to gas) at room temperature and pressure. This is why it slowly disappears if left exposed to air.

• Density: 0.99 g/cm³ at 25 °C. It is slightly less dense than water and will float.

• Solubility:

  • Water: Very slightly soluble (approx. 1.2 g/L at 25 °C).

  • Organic Solvents: Highly soluble in ethanol, ether, chloroform, carbon disulfide, and fixed and volatile oils (like turpentine oil).

  • Other Solvents: Soluble in concentrated ammonia and Dimethyl Sulfoxide (DMSO).

• Flash Point: 64 °C (closed cup).

• Optical Activity: Naturally occurring camphor from Cinnamomum camphora is dextrorotatory (+)-camphor. Synthetic camphor is typically the optically inactive racemic (DL-) mixture.

4. Production Methods

• Natural Production (Historical): The traditional method involves steam distillation of the chipped wood, roots, and branches of the camphor tree (Cinnamomum camphora). The distilled essential oil is then cooled, allowing the crude camphor to crystallize. This is further purified by sublimation or recrystallization.

• Synthetic Production (Modern Method): Today, the vast majority of the world's camphor is synthesized from α-pinene, a major component of turpentine oil obtained from pine trees. The synthesis involves a multi-step chemical process:

  1. Isomerization: α-pinene is converted to camphene.

  2. Esterification: Camphene is reacted with acetic acid to form isobornyl acetate.

  3. Hydrolysis: Isobornyl acetate is hydrolyzed to isoborneol.

  4. Oxidation: Finally, isoborneol is oxidized (dehydrogenated) to yield camphor.

• Purity Grades:

  • Technical/Industrial Grade: Used in the production of plastics (like celluloid), as a plasticizer, and in chemical synthesis. It may contain impurities.

  • Pharmaceutical/Food Grade: Highly purified (>99%) to meet strict safety standards for use in topical medications, cosmetics, and as a flavoring agent.

5. Applications and Uses

Camphor's unique properties make it useful across a diverse range of industries.

• Pharmaceutical and Medical Applications:

  • Topical Analgesic: A common ingredient in over-the-counter creams, ointments, and balms for relieving minor muscle and joint pain, arthritis (often combined with chondroitin sulfate and glucosamine sulfate), and backaches.

  • Anti-inflammatory and Antipruritic: Used in lotions (e.g., calamine lotion) to reduce itching and minor skin inflammation from insect bites or rashes.

  • Antimicrobial: Exhibits mild antibacterial and antifungal properties, contributing to its use in some topical antiseptic preparations.

  • Cough Suppressant and Decongestant: Its strong, penetrating vapor is believed to act as a mild expectorant and nasal decongestant. It is a key component in vapor rubs and inhalants used for cold and cough symptom relief.

• Industrial Applications:

  • Plasticizer: Historically crucial in the production of celluloid, one of the first commercial plastics. It is added to nitrocellulose to make it flexible and moldable. It is still used in some specialty plastics and films.

  • Chemical Intermediate: Used as a starting material in the synthesis of other organic compounds, including certain fragrances and pharmaceuticals.

  • Stabilizer: Employed as a stabilizer in some explosives and pyrotechnics.

• Other Applications:

  • Fragrance and Flavoring: Widely used to impart its characteristic scent in soaps, detergents, air fresheners, and industrial cleaning products. In very low concentrations, it is used as a flavoring agent in some foods, confectionery, and liqueurs.

  • Traditional and Alternative Practices: Has historical use in religious ceremonies (e.g., in India for burning in lamps), as an insect repellent, and in some traditional medicine systems for conditions like anxiety or hair loss, though scientific evidence for these uses is often lacking.

6. Toxicology and Safety Profile

While beneficial in controlled doses, camphor can be highly toxic if misused.

• Acute Toxicity: Ingestion of even small amounts (toxic dose is ~500 mg for children, ~2 g for adults) can lead to serious poisoning. Symptoms include nausea, vomiting, a burning sensation in the mouth and throat, confusion, agitation, muscle spasms, and potentially life-threatening seizures (convulsions). The estimated lethal dose (LD50) for adults is approximately 50-500 mg/kg.

• Overdose Symptoms: Camphor poisoning is a medical emergency. Early signs are gastrointestinal distress followed by central nervous system excitation, leading to epileptiform convulsions, respiratory depression, and coma.

• Contraindications and Precautions:

  • Pregnancy and Breastfeeding: Its use is generally contraindicated as it may cross the placenta and has been associated with uterine stimulation and potential harm to the fetus. It can also be excreted in breast milk.

  • Children and Infants: Highly dangerous for children. Products containing camphor should be kept out of reach. The use of high-concentration camphor rubs on infants and young children is associated with a risk of seizures.

  • Broken or Damaged Skin: Should not be applied to open wounds or severely irritated skin, as this can significantly increase systemic absorption and the risk of toxicity.

  • Liver Disease: As camphor is metabolized in the liver, individuals with liver impairment may be at higher risk of adverse effects.

  • G6PD Deficiency: There is some evidence that camphor may trigger hemolytic anemia in individuals with Glucose-6-Phosphate Dehydrogenase (G6PD) deficiency.