Alcohols — Structure, Properties and Uses — AQA GCSE Chemistry (Separate)

Alcohols are a homologous series with the –OH functional group, used as fuels, solvents and in drinks.

The alcohol series

Alcohols all contain the hydroxyl functional group, –OH. The first four are:

• methanol (CH₃OH)
• ethanol (C₂H₅OH)
• propanol (C₃H₇OH)
• butanol (C₄H₉OH)

Properties and reactions

Alcohols:

• Dissolve in water to form a neutral solution.
• React with sodium to produce hydrogen.
• Burn (combust) in air, releasing energy: e.g. ethanol + oxygen → carbon dioxide + water.
• Are oxidised by microbes/air to form carboxylic acids (e.g. ethanol → ethanoic acid, which is why wine turns to vinegar).

Making ethanol

• Fermentation of sugars by yeast (anaerobic): sugar → ethanol + carbon dioxide. Done at around 30 °C.
• Hydration of ethene with steam (industrial addition reaction).

Uses of alcohols

• Solvents (dissolving substances that don't dissolve in water).
• Fuels (e.g. ethanol in some car fuels).
• In alcoholic drinks (ethanol).

Exam tips

• The functional group is –OH; learn the first four alcohols.
• Alcohols dissolve in water, react with sodium, and burn.
• Ethanol is made by fermentation (yeast) or hydration of ethene.
• Alcohols oxidise to carboxylic acids.