In this video, you will learn the some of the chemical properties of alcohols, how to
classify alcohols and some uses of alcohols.
Alcohols are organic molecules with the hydroxyl functional group, which is an oxygen bonded
to a hydrogen OH.
Here is methane – replace a hydrogen with the alcohol functional group to form methanol.
Here is ethane and here is ethanol.
Propane and propanol.
Pause the video and name this molecule (butanol).
The general formula of the alcohols is CnH2n+1OH The OH group generally makes alcohols polar
molecules.
The hydroxyl group also gives rise to hydrogen bonding.
In our video on fractional distillation, we discussed how increasing chain length increased
the boiling point due to increased intermolecular forces.
The alcohols follow this same trend but their boiling point is even higher than their comparable
alkane and this is due to hydrogen bonding.
Alcohols are placed into one of three cateories, primary, secondary or tertiary based on the
position of the OH on the chain.
Alcohols will react differently depending on the group they are in.
In a primary alcohol, the carbon atom on which the OH group bonded, is itself attached to
only one carbon chain, or one alkyl group.
Here is propan-1-ol.
The OH is attached the end carbon and this carbon is attached to just the single chain
of carbons.
In secondary alcohols, the carbon atom on which the OH group is bonded is attached to
two carbon chains or two alkyl groups.
Here is propan-2-ol.
Here is the carbon atom on which the OH is attached and here you can see the two alkyl
groups or two carbon chains attached to this carbon – one here and another here.
These two alkyl groups make this a secondary alcohol.
In tetriaty alcohols, there are three carbon chain attached to the carbon on which the
OH is attached.
Here is 2-methyl-propan-2-ol.
As you can see, the carbon attached to the OH group is attached to three alkyl groups
making it a tertiary alcohol.
It is important to categorise an alcohol as they have slightly different chemical properties.
A good example of this that you could look into as further reading, would be the oxidation
of the alcohols with different reactions occurring for primary, secondary alcohols and tertiary
alcohols.
Different alcohols have different uses at home and in industry.
Ethanol is of course a common alcohol used in beverages but is also an important antiseptic!
Ethanol can be made by two main methods – by fermentation and by the hydration of ethane.
We have made a video on these methods to learn about these in more detail.
Other uses of alcohols are as fuels, preservatives and solvents.
Now at the end of this tutorial, you should be able to identify the alcohol functional
group and name alcohols, understand their uses and be able to categorise them as primary,
secondary or tertiary.