Chemistry only

So far you will probably have met two homologous series of organic compounds:

Well your about to meet another homologous series- The alcohols. In naming the alkanes and alkenes we have met so far you may have noticed that the first part of their names were similar. Well there is a reason for this, the first part of the name will help you in identifying the number of carbon atoms in a compound. So for example, the prefix meth- will tell you the substance has 1 atom of carbon it, while the prefix oct- will tell you the molecule has 8 atoms of carbon in it. Just as the names of all alkanes end in -ane and all alkenes end in -ene, well the names of alcohols end in -ol. The prefixes you will have used to name alkanes and alkenes are:

Prefix meth eth prop but pent hex hept oct non dec
number of carbon atoms 1 2 3 4 5 6 7 8 9 10
alcholic drinks

The table above gives the prefixes used for compounds with up to nine carbon atoms in them. Just as all alkenes contain the functional group C=C and all alkanes contain the functional group C-C, well all alcohols contain the functional group C-O-H or C-OH, you may see it written both ways. It is this hydroxyl group, C-OH which gives alcohols their characteristic properties.

The most widely known alcohol is ethanol, this is the alcohol which is used in alcoholic drinks, it is made in a process called fermentation. The table above can help you name the first 10 alcohols. The first alkane was methane, remove the -e from the end and replace with -ol and you have the first alcohol, methanol. Similarly the second alkane was ethane, the second alcohol is ethanol, also propane becomes propanol, butane becomes butanol etc. Models of the first three alcohols, methanol,ethanol and propanol are shown below.

The first three alcohols

first three alcohols

The alcohols form a homologous series with the general formula CnH2n+1OH. The full structural formula for the first 5 alcohols are shown below. You should note all alcohols contain the hydroxyl functional group, C-OH, and it is this group which determines how alcohols react.

structural formula for alcohols

Uses of alcohols

The main uses of alcohols are in alcoholic drinks (ethanol only) such as wine, beer and spirits, as a solvent in cosmetics and perfumes. Alcohol is flammable and makes an excellent fuel. In the UK at the petrol pumps the fuel is a mixture of petrol and up to 10% ethanol, some racing cars even run on a 85:15 % mixture of petrol to ethanol. Perhaps one of the most high profile uses in current times is as a hand sanitizer in gels to kill corona-virus.

Uses of alcohols

Key Points

Practice questions

Check your understanding - Questions on alcohols