What is Camphor?

A terpene with the molecular formula of C₁₀H₁₆O is a waxy, white color  solid known as camphor. It is flammable. It also possesses a very pungent taste and a strong odor. There are various sources for extracting camphor from natural products such as the wood of the tree of camphor laurel. Sublimation of wood and steam distillation are some of the methods involved in obtaining camphor.  

Structure of Camphor

It is a monoterpenoid which at the second position bears an oxo group also known as cyclic monoterpene ketone and a bornane derivative. The naturally occurring camphor is the (+)-camphor and its enantiomer is the (-)-camphor. They are mirror images of each other. The camphoraceous odor is present in both the enantiomers. The IUPAC name of camphor is 1,7,7-trimethylbicyclo[2.2.1]-2-heptanone. 

Before the structure of camphor was properly revealed, a lot of effort had to be done. The functional nature of the oxygen atom was shown to be oxo by the fact that camphor formed an oxime. The keto group was discovered due to the fact that oxidation of camphor produces a dicarboxylic acid with ten carbon atoms, while monocarboxylic acid with ten carbon atoms is impossible to acquire. 

As can be observed from the above, camphor's parent hydrocarbon has the chemical formulaC₁₀H₁₈, which translates toC_nH_2n-n, making it bicyclic. Because camphor creates an oxide with nitrous acid, it has a -CH₂CO group. Finally, p-cymene is obtained by distilling camphor with zinc chloride. 

Stereochemistry of Camphor 

Camphor, like camphoric acid, contains two different chiral centers, but only one pair of enantiomers is recognized. Because only the cis form is possible, this is the case. The boat conformation is adapted by camphor and its derivatives. 

Physical Properties of Camphor 

The waxy and white solid that undergoes sublimation at room temperature is the basic physical property of camphor. It is not soluble in water but soluble in organic solvents such as chloroform, ether, and alcohol. Through the distillation of the Camphor Laurel tree wood naturally occurring camphor is obtained and the synthetic camphor is synthesized from a substance obtained from the turpentine oil known as α-pinene. In many aromatic species of plants, camphor is known to be present in the form of essential oil components.  

Synthesis of Camphor

The starting material for the biosynthesis of camphor is  geranyl diphosphate (GPP) present in the plant as the substrate. Further, the enzyme (+)-bornyl diphosphate synthase is involved to carry out cyclization and subsequent hydrolysis gives the (+)-borneol. This compound is oxidized to give (+)-camphor. 

The starting material for producing camphor synthetically is turpentine oil. The α-pinene is extracted from this turpentine oil through distillation. The conversion of α-pinene to camphene is carried out in acetic acid using strong acid catalysis. Further, the formation of isobornyl cation is through the Wagner-Merwin rearrangement it undergoes hydrolysis and subsequent dehydrogenation to give camphor in a racemic mixture(1:1)

Camphor as a Chiral Auxiliary and Starting Material

Due to the abundance and economically favorable status of monoterpenes, they have been widely employed as starting material or chiral synthons for synthesis. In various chemical reactions, camphor and its derivatives are used as catalysts and chiral auxiliary that introduce chirality in a molecule. The camphor sulfonic acid (CSA) is widely used as a catalyst for reducing molecules chirally. It is an organic acid derived from camphor. The aromatic steroids are synthesized using camphor as the starting material. Thus, there are various applications for the camphor structure and its derivatives in the world of synthesis. 

Camphor as a Medicinal Product 

Camphor is known to have a lot of medicinal properties since ancient times. Especially in Asia, it is known to possess deep significance. Some medicinal uses of camphor involve chest congestion relief and as a remedy for cold. It is also known to work with inflammation in the body. The oil, cream, or balm produced from camphor is well-known to have anti-inflammatory properties and relieves pain from muscular joints. Camphor oil is also known as a cooling agent involved with stimulating nerve endings. It is used to soothe areas causing irritation, itching, or pain.  

The use of camphor by combining it with other treatments has been proved to be very effective in various references. It can also help in the prevention of some serious diseases.  

Camphor and its Toxicity

As much as it has medicinal properties camphor is also known for its toxicity upon ingestion. The reports stated that when 3.5g of camphor was taken it caused fatality while 2.0g ingestion caused gastrointestinal tract, kidney, and brain congestion. It was also reported that an infant immediately collapsed after applying a small dose of camphor to the nostrils.

Camphor poisoning causes some characteristic symptoms such as dizziness, headache, vomiting, and nausea. In case of overdose, it is several hours of epilepsy followed by coma and fatality. Since no antidote has been found camphor poisoning treatment is targeted towards its symptoms only. Due to the presence of camphor in various aromatic species of plants they are found to be toxic and under investigation. 
 

Camphor in Nano Technology

Camphor is also used as a carbon source for carbon nanotubes. In the medicinal and industrial field, carbon nanotube has made various developments owing to its selectivity and drug delivery. With reference to cancer, carbon nanotubes due to their strong fibrous and light nature, this tube of a sheet of single-atom thickness provided a large surface area and accurate drug delivery. Also, the excretion of this product is devoid of toxicity, and therefore it is widely used. However, no environment-friendly method has been discovered for the source of carbon till this point. It is generally obtained from petroleum products such as acetylene, benzene, methane, and etc. therefore the introduction of camphor as the source of carbon will change the eco-value of carbon nanotubes application. There is no fear of shortage for camphor-like the petroleum product due to the natural abundance of it and cost economical features. The production of carbon from camphor also gave high yield and purity for carbon nanotubes along with high efficiency. Camphor can be seen as the future for carbon nanotechnology. 

Context and Applications 

This topic is significant in the professional exams for both undergraduate and graduate courses, especially for Chemistry.