chemistry c7

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

Synthesis

Fermentation

Biotechnology

Ethanol is used on an industrial scale as a feedstock, solvent and fuel.

Synthesis

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

Fermentation

Ethanol for use in alcoholic drinks (e.g. wine) is produced in the following way:

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