2.Classification

• Alcohols and phenols may be classified as mono–, di–, tri- or polyhydric compounds depending on whether they contain one, two, three or many hydroxyl groups respectively in their structures as given below

• Monohydric alcohols may be further classified according to the hybridisation of the carbon atom to which the hydroxyl group is attached.

(i) Compounds containing C sp3 - OH bond: In this class of alcohols, sp

the –OH group is attached to an sp3 hybridised carbon atom of an alkyl group. They are further classified as follows:

• Primary, secondary and tertiary alcohols:

• In these three types of alcohols, the –OH group is attached to primary, secondary and tertiary carbon atom, respectively

• Allylic alcohols: In these alcohols, the —OH group is attached to a sp3 hybridised carbon adjacent to the carbon-carbon double bond, that is to an allylic carbon. For example

• Benzylic alcohols: In these alcohols, the —OH group is attached to a sp3—hybridised carbon atom next to an aromatic ring.

• For example

• Allylic and benzylic alcohols may be primary, secondary or tertiary.

• (ii) Compounds containing C sp2 OH bond:

• These alcohols contain—OH group bonded to a carbon-carbon double bond, i.e., to a vinylic carbon or to an aryl carbon. These alcohols are also known as vinylic alcohols.
  Vinylic alcohol: CH2 = CH – OH

• Phenols— Mono, Di and trihydric phenols:

• 

• Ethers are classified as simple or symmetrical

• if the alkyl or aryl groups attached to the oxygen atom are the same, and mixed or unsymmetrical, if the two groups are different.

• Diethyl ether, C2H5OC2H5, is a symmetrical ether whereas C2H5OCH3 and C2H5OC6H5 are unsymmetrical ethers.