TOP OF PAGE and sub-index

TOP OF PAGE and sub-index

Examples of naturally occurring aromatic compounds - the natural occurrence of the benzene ring!

 Use of the term 'aromatic' derives from the smell of oil from natural products - usually 'aromatic' plants.

Today the term refers to compounds containing a benzene ring, fused benzene rings or other ringed compounds that chemically behave as an aromatic compound.

Aromatic compounds from the natural world often have a strong pleasing smell and are naturally found in wine, spices, perfumes, fragrance oils, and essential oils extracted from plants.

The simplest aromatic aldehyde, benzaldehyde (right) smell's of almonds and is a naturally occurring compound found in bitter almond oil. It is synthesised by the chemical industry for use in food flavourings and fragrances in the perfume industry.

Salicin (below) is a naturally found in the bark of willow and poplar trees. For thousands of years it was known to have a pain-killing action when ingested, it is an anti-inflammatory agent. The Salicin molecule consists of a phenol attached by an ether linkage to hexose sugar molecule.

 The search for molecules having a similar effect. Salicylic acid (2-hydroxybenzoic acid) is derived from the metabolism of Salicin and is used in medical treatment. However, synthetic acetylsalicylic acid (Aspirin) was found to be a more effective painkiller. Soluble Aspirin is absorbed more quickly minimising irritating the stomach.

An 'aspirin' related aromatic acid derived molecule is C₈H₈O₃, or , methyl 2-hydroxybenzoate.

Commonly known as methyl salicylate or 'oil of wintergreen', a molecule that has mild pain killing properties. This methyl ester of salicylic acid is a colourless, viscous liquid with a sweet, fruity minty odour and used in mint candies. It  is produced by many species of plants, particularly wintergreens, from which it can be obtained by distillation. These days it is mostly manufactured synthetically, by esterifying 2-hydroxybenzoic acid with methanol, and used as a fragrance and flavouring agent.

Many plants produce methyl salicylate in small quantities, often in response to biotic stress e.g. infection by pathogens, where it plays a role in the induction of resistance. Methyl 2-hydroxybenzoate is also released in some plants when they are damaged by herbivorous insects, where they may function as a cue aiding in the recruitment of predators. Some plants produce methyl salicylate in larger quantities to aid direct defence against predators or pathogens

The benzene ring even turns up opiates (a type of alkaloids) such as naturally occurring morphine, codeine and heroin, but these are not classed as aromatic compounds.

For more on uses see my organic chemistry notes Parts:

7.5 Electrophilic substitution - ring nitration of benzene and methylbenzene, properties and uses of nitro-aromatics

7.7 Electrophilic substitution - ring sulfonation of arenes, properties & uses of alkylbenzenesulfonic acids

7.9 The physical and chemical properties of phenol and some of its derivatives and their uses

7.10 Physical & chemical properties of phenylamine, selected derivatives including diazonium ions and dyes

7.12 The structure, properties and uses of polyesters and polyamides involving aromatic monomers