Alcohols are organic molecules containing the OH, hydroxyl, functional group and are named after their parent alkane …
If the molecule contains more than one OH group, then the alkane part of the name retains the ‘e’ (who knows why?) …
Alcohols are classified as primary, secondary or tertiary depending on how many alkyl groups are bonded to the carbon atom that is also bonded to the OH group – it is important to be able to recognise the difference as it has a direct bearing on the way they react with oxidising agents.
Alcohols are deprotonated (they lose the hydrogen from the OH group) in reactions with strongly reducing metals such as lithium, sodium or potassium, or in reactions with metal hydrides such as sodium hydride, NaH. The organic product of the reaction is a metal alkoxide.
e.g. 2CH3OH + 2Na ⇾ 2CH3O–Na+ + H2
Sodium methoxide, like many metal alkoxides, is a useful base or nucleophile in synthesis reactions. They are simply named from the metal cation and the alcohol changing its ending to ‘oxide’ …
Ethers are relatively inert isomers of alcohols where the oxygen is sandwiched between two alkyl groups and they are named as substituted alkanes …
Practice questions
- Name the functional groups bonded to the benzene ring in salicylic acid.
- Salicin is a compound found in willow bark that the body is able to convert to salicylic acid. Determine how many primary, secondary and tertiary alcohol groups are present in the compound.
- Draw the full structural formulae of the six isomers of butan-1-ol.
- Ethoxypropane is an isomer of pentan-3-ol. Draw the skeletal structure of both molecules.
- Name the following ethers:
Answers
- phenol, carboxylic acid
- there are 2 primary alcohol groups and three secondary alcohol groups
4.
5. (a) 1-methoxybutane
(b) 2-methoxybutane