The Chemistry of Eugenol

Every year when Christmas time comes up, we are surrounded by a plethora of scents at home or in shopping centres. The most distinctive of these are from spices, and especially cloves which contain eugenol as pictured below.


Eugenol or 2-Methoxy-4-(prop-2-en-1-yl) phenol is a pale yellow oily liquid at room temperature. It belongs to the homologous series of phenylpropene which make up many essential oils. Eugenol is mainly present in cloves which are the flower buds of the S. aromaticum tree, accounting for around 80% and gives them their characteristic smell as spices.

It is also found in bay leaves and allspice, and other botanical oil, but in lower concentrations, much of these are used around Christmas time as well. The oil also contains a myriad of other compounds which increases the versatility of cloves including about 10% acetyl eugenol and small quantities of gallic acid, sesquiterpenes, furfural, methyl-n-amyl ketone and vanillin which gives the characteristic smell of vanillin.

vanillinSince eugenol is chemically similar to vanillin it was previously used to undergo double bond migration to form isoeugenol which underwent oxidation to form vanillin.

Surprisingly, eugenol is used in dentistry for fillings and prosthetics. It is combined with zinc oxide forming zinc oxide eugenol (ZOE). Due to the anaesthetic and antibacterial properties of eugenol, it is used as a temporary filling to sedate the tissue inside the tooth.

So there we have it, eugenol not only makes Christmas smell Christmassy but can be changed to smell like vanilla and also help out in dentistry.

Author – Jiangmin Hou
Jiangmin is a 6th year high school student currently studying three STEM subjects at Scottish Advanced Higher level including Mathematics, Biology, and Chemistry. She is interested in pursuing a degree in Medicine after completion of Secondary Education.


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