Uses of alcohol
Methanol can be used as a chemical feedstock and also in the manufacture of cosmetics.
Ethanol can be used as a solvent and also as a fuel.
Physical properties of alcohols
The properties of different alcohols can be explained by comparing their structures:
Shorter alcohols have a low boiling point because the intermolecular forces are weak and don’t need much energy to overcome them.
Longer hydrocarbons are less soluble in water because they behave more like an alkane, so they tent to float on top of the water due to their low density.
Reaction of alcohols with Sodium
Alcohols react with sodium to produce a salt and hydrogen gas.
Alcohols, water and alkanes react differently with sodium:
Sodium sinks in alcohol, doesn’t melt and steadily gives off hydrogen
Sodium floats on water, melts, rushes around on the surface and rapidly gives off hydrogen
There is no reaction between sodium and an alkane
Reaction of alcohols with air
Alcohols burn in air because of the presence of a hydrocarbon chain
The production of ethanol
Ethanol can be produced by
Ethanol is used on an industrial scale as a feedstock, solvent and fuel.
the following steps lead to the product of ethane, which can be used to produce ethanol.
1. Crude oil undergoes fractional distillation
2. Long chain hydrocarbons (alkanes) are vaporised and then cracked using a catalyst and heat
3. The molecules are purified using fractional distillation
4. The ethene that’s produced can be used for a feedstock and the remaining water is removed.
Ethene is then reacted with steam at a high temperature and pressure in the presence of a catalyst to produce ethanol:
Ethene + steam -> ethanol
C2H4 (g) + H2O (g) -> C2H5OH (g)
Any unreacted products are recycled and fed through the system again
Ethanol for use in alcoholic drinks (e.g. wine) is produced in the following way: