Limonene.
What is it?
Limonene is from a family of hydrocarbons produced by plants-known as terpenes. Limonene is an orange terpene. Terpenes are present in essential oils, especially citrus oils, which in turn can be used for many things such as natural food flavourings, fragrances and aromatherapy. There are two main types of terpenes; cyclic and acrylic.
What is its structure and properties?
Limonene is an alkene, meaning its functional group is C=C, its suffix is-ene and its formula is CnH2n. Its full name is 1-methyl-4-prop-1-en-2-yl-cyclohexane. Limonene melts at -95.2c and it boils at 176c, therefore Limonene is liquid at room temperature. It is lighter than water and insoluble in water, unless a surfactant is added. D-limonene is considered a combustible liquid. Limonene is a cyclic terpene.
Where is it found and how is it made?
As mentioned before, Limonene is a member of the terpene family. It is found in large quantities in the skin of citrus fruits. It’s extracted from the rind of citrus fruits during juicing. After which, the rind is pressed to get the oil out, and then the oil is separated from the fruit juice and distilled, this recovers its fragrance and flavour compounds. The result is food grade d-limonene, which is 96-97% pure and has a mild orange scent. When the juicing process is completed, more oil is removed from the peel in a steam extractor. After the peel is steamed and the steam condenses, a layer of oil is left floating on the top of the water. This is technical grade d-limonene, which is about 5% pure and has a very strong orange scent. It is limonene that gives citrus fruits their scent.
What is it used for?
As mentioned above Limonene can be used as a natural flavouring in food. Also, due to its strong scent it is used in cleaning products to give them a citrus smell. It can be used a paint stripper and as an environmentally friendly alternative to mineral oils. It is also a very effective pesticide. It is a contact poison which intensifies sensory nerve activity in insects.
What could it be used for in the future?
Limonene can be used as an alternative to mineral oils. Obviously mineral oils are a non-renewable source and they are not biodegradable. Because it is from a natural source, limonene does not release anything that would not occur naturally anyway. Therefore it is an environmentally preferred product.
What are its hazards and what precautions should be taken with it?
Limonene is flammable and it is a skin, eye and mucous membrane irritant. If a high dose of limonene is received it can cause tremors, lack of co-ordination and muscle weakness, though these symptoms are temporary. It is biodegradable, but it must be treated as hazardous waste.
