Reactions of benzene ring: · Part 2

first converted into sodium phenoxide which is more reactive than phenol towards electrophilic substitution reaction with CO . Treatment of sodium phenoxide with CO at 400K, - bar pressure followed by acid hydrolysis gives salicylic acid. NaOH 400K H + /H O +CO - bar Salicyclic acid ONa COONa COOH phenol sodium phenoxide sodium salicylate vi) Riemer – Tiemann Reaction: On treating phenol with CHCl /NaOH, a -CHO group is introduced at ortho position. This reaction proceeds through the formation of substituted benzal chloride intermediate. CHCl aq.NaOH phenol H + CHCl NaOH O - Na + CHO CHO Salicylaldehyde Na XII U11-Hydroxy XII U11-Hydroxy - - - - vii) Phthalein reaction: On heating phenol with phthalic anhydride in presence of con.H SO , phenolphthalein is obtained. Con H SO phthalic anhydride Phenolphthalein HO Phenol viii) Coupling reaction: Phenol couples with benzene diazonium chloride in an alkaline solution to form p-hydroxy azobenzene(a red orange dye). N Cl + NaOH p-hydroxy azobenzene -278K Benzene diazonium chloride Phenol Test to differentiate alcohol and phenols i) Phenol react with benzene diazonium chloride to form a red orange dye, but ethanol has no reaction with it. ii) Phenol gives purple colouration with neutral ferric chloride solution, alcohols do not give such coloration with FeCl . iii) Phenol reacts with NaOH to give sodium phenoxide. Ethyl alcohol does not react with NaOH . Uses of phenol ) About half of world production of phenol is used for making phenol formaldehyde resin. (Bakelite). ) Phenol is a starting material for the preparation of i) drugs such as phenacetin, Salol, aspirin, etc. ii) phenolphthalein indicator. iii) explosive like picric acid. ) It is used as an antiseptic-carbolic lotion and carbolic soaps. XII U11-Hydroxy XII U11-Hydroxy - - - - Evaluate Yourself . Which of the following set of reactants will give -methoxy- -nitrobenzene. + CH ONa (i) Br O N (ii) + CH Br ONa O N . what happens when m-cresol is treated