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Science

Smells

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Esters are made by reacting an alcohol with an organic acid. They are used in perfumes, and as solvents. Nail varnish dissolves in nail varnish remover, but not in water.

Perfumes

Perfumes have a pleasant smell and they stimulate receptors in the nose. Some perfumes are obtained from natural sources, such as lavender oil or sandalwood oil. Others are made synthetically.

Commercial perfumes need particular properties to be successful. The table summarises these properties and why they are needed.

Summary of the properties of perfume

propertywhy the property is important
non-toxicdoes not poison the wearer
does not irritate the skinprevents the wearer from suffering rashes
evaporates easily - very volatileperfume molecules reach the nose easily
insoluble in waterit is not washed off easily
does not react with wateravoids the perfume reacting with perspiration

Volatility - Higher tier

Volatile liquids evaporate easily. They readily change from a liquid to a gas. This is because there are only weak attractive forces between particles in the substance. These forces are overcome easily, so particles with enough energy can escape from the liquid.

Esters

Esters are chemicals with pleasant smells. They are used in perfumes, and as solvents.

Making esters

Esters occur naturally, but can be made in the laboratory by reacting an alcohol with an organic acid. A little sulfuric acid is needed as a catalyst. This is the general word equation for the reaction:

alcohol + organic acid    →    ester + water

For example:

methanol + butanoic acid    →    methyl butanoate + water

The diagram shows how this happens, and where the water comes from:

One hydrogen comes from the alcohol molecule. One oxygen and another hydrogen comes from the organic acid. These two hydrogens and  oxygen form a water molecule. The remains of the alcohol and organic acid join to form an ester.

Making esters

What esters smell like

Different esters have different smells.

alcoholorganic acidester madesmell of ester
pentanolethanoic acidpentyl ethanoatepears
octanolethanoic acidoctyl ethanoatebananas
pentanolbutanoic acidpentyl butanoatestrawberries
methanolbutanoic acidmethyl butanoatepineapples

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