From haloarenes
Chlorobenzene is fused with NaOH at 623K and 320 atmospheric
pressure Phenol is obtained by acidification of sodium phenoxide so
produced (Unit 6, Class XII) 2 From benzenesulphonic acid
Benzene is sulphonated with oleum and benzene sulphonic acid so
formed is converted to sodium phenoxide on heating with molten
sodium hydroxide