This topic accounts for approximately 6% of your exam marks.
stable
Low
Stable6%
Fermentation vs hydration routes and uses of ethanol are commonly tested.
What an alcohol is
Alcohols are a homologous series of organic compounds that contain the hydroxyl functional group, −OH
The hydroxyl group is what fixes the chemistry of every alcohol — it can be oxidised, react with carboxylic acids to form esters, and is responsible for the alcohol being a polar molecule that dissolves in water
The short alcohols are colourless liquids at room temperature; they mix fully with water and the resulting solution is neutral on the pH scale
Methanol, ethanol, propanol and butanol — the first four members of the series — are all used either as fuels or as solvents
General formula of the alcohol homologous series:
CnH2n+1OH
The naming rule is the standard stem-plus-ending convention from topic 21: replace the final "-e" of the parent alkane with "-ol"
meth-an-e + -ol → methanol
eth-an-e + -ol → ethanol
prop-an-e + -ol → propanol (numbered as propan-1-ol or propan-2-ol when the position of −OH matters)
The first four alcohols
Position of the −OH on longer alcohols
For propanol and onwards, the hydroxyl group can sit on different carbons in the chain; a number between the stem and the "-ol" shows which carbon
Propan-1-ol has the −OH on carbon 1 (the end of the chain): CH3CH2CH2OH
Propan-2-ol has the −OH on carbon 2 (the middle): CH3CH(OH)CH3
In IGCSE Chemistry exams, "propanol" and "butanol" without a number always mean the propan-1-ol and butan-1-ol isomers