Chlorobenzene and Phenol

Page 1

Cyclohexane

Chloroalkanes such as 1-chlorohexane react with aqueous sodium hydroxide when heated under reflux, giving hexan-1-ol as the main product

CH3-(CH2)4-CH2-Cl + NaOH(aq) ==> CH3-(CH2)4-CH2-OH + NaCl

This is an example of Nucleophilic substitution.

Page 2

C-Cl bonds and Chlorobenzene

Benzene tends to react by electrophilic substitution rather than by nucleophilic substituions, which is due to the delocalised ring (stable pi system).

The stronger and shorter C-Cl bond in chlorobenzene results from a non-bonding P electron pair on chlorine overlapping with the pi system. The resulting bond needs more energy to be broken and is thus therfor stronger than an aliphatic C-Cl bond. Therefore, forcing conditions are needed to produce phenol from chlorobenze. These conditions are aqueous sodium hydroxide, 300 degrees celcius and increased pressure.

Tis is not an environmentally viable method of commercially producing phenol.

Therefore, in industry, phenol is generally made from (1-methyl, ethyl) benzene. This method has the advantage that propanone is a useful biproduct of the reaction.