3.2.10 Alcohols, aldehydes, ketones and carboxylic acids - Nomenclature
Students should:
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Naming alcohols
If the alcohol group (OH) is the priority group in the molecule it is returned as a suffix - anol.
methanol
Once the molecules have 3 or more carbon atoms, it is important to name the position of the -OH group by placing a number between the 'an' and the 'ol using dashes.
Note: An alternative and accepted way of numbering the position of the alcohol (OH) group is to place the number before the name:
e.g 
1-propanol,
2-propanol
etc.
Organic priorities
Organic chemistry nomenclature priorities are in order of the degree of oxidation of the carbon atom. This can be calculated by adding up all of the oxidation numbers of the oxygen, hydrogen or other heteroatoms.
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Carboxylic acid group -COOH has to add up to -1 (it bonds to a hydrogen atom, +1) Hence C + (2 x O) + H = -1 Therefore: C = +4 - 2 = +2 |
So, the oxidation state of carbon in the carboxylic acid group = +2
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Aldehydes In the aldehyde group -CHO the oxidation states of the constituent atoms once again must add up to -1 Hence: C + O + H = -1 Therefore C = 0 |
The aldehyde group carbon can be considered to have an oxidation state of zero.
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Ketones In a ketone, the C=O group could attach to two hydrogen atoms and must be -2 Hence: C + O = -2 Therefore C = 0 |
The oxidation state of the carbon atom in the ketone group is zero.
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Ketones In the alcohol group -CH2OH, the oxidation states of the atoms must once again add up to -1 Hence: C + (3 x H) + O = -1 Therefore C = -2 |
So, the alcohol group has a carbon atom with a oxidation state of -2
Naming aldehydes
Aldehydes can only be placed at the end of a chain. The name is given by adding -anal to the root number of carbon atoms.
Note that the carbon atom in the aldehyde group counts towards the total number of carbon atoms in the chain.
Naming carboxylic acids
Carboxylic acids can only be placed at the end of a chain. They are named by adding '-anoic acid' to the root number of carbon atoms.
Note that the carbon atom in the carboxylic acid group counts towards the total number of carbon atoms in the chain.