����tv

Uses of the first four alcohols

Methanol is used as a chemical feedstock. It is toxic, so it is deliberately added to industrial ethanol (methylated spirits) to prevent people from drinking it.

Ethanol is the alcohol present in alcoholic drinks. It is also used as a fuel and a solvent.

Propanol and butanol are also used as solvents and fuels.

Combustion

The alcohols undergo complete combustion to form carbon dioxide and water. For example, ethanol is used as a fuel:

ethanol + oxygen → carbon dioxide + water

C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O

When less oxygen is present, incomplete combustion will occur, producing water and either carbon monoxide or carbon.

Reactions with sodium

If a small piece of sodium is dropped into ethanol, bubbles of hydrogen gas are produced and the liquid contains sodium ethoxide. The reaction is:

sodium + ethanol → sodium ethoxide + hydrogen

2Na + 2C₂H₅OH → 2C₂H₅ONa + H₂

Methanol, propanol and butanol undergo similar reactions.

Solubility in water

When the alcohols with the shortest hydrocarbon chains, eg methanol, ethanol or propanol, are added to water, they mix easily to produce a solution. However, the solubility decreases as the length of the alcohol molecule gets longer, so butanol is less soluble than propanol. It may not mix easily, and two distinct layers might be left in the container.

Oxidation of alcohols

The alcohols can also be oxidised without combustion to produce carboxylic acids. For example, ethanol can be oxidised to ethanoic acid using an oxidising agent.

It is easier to understand what happens if ethanol is shown as CH₃CH₂OH in the balanced equation:

ethanol + oxidising agent → ethanoic acid + water

CH₃CH₂OH + 2[O] → CH₃COOH + H₂O

Each of the two oxygen atoms provided by the oxidising agent are shown as [O]. Notice that the left-hand side of the ethanol molecule is unchanged. The reaction involves the -OH group on the right-hand side.