244 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



Benzene Sulphonyl Chloride. 



Benzene sulphonic acid or its salts are converted by the action of phos- 

 phorus pentachloride into benzene sulphonyl chloride : 



C 6 H 5 . SO 2 OH + PCl g = HC1 + POClg + C 6 H 5 SO 2 C1. 



The two substances are heated on a water-bath till hydrochloric acid is no 

 longer evolved. The product is poured into water and the sulphonyl chloride 

 extracted with ether. It is purified by distillation in vacua. 



Benzene sulphonyl chloride is a white solid which melts at 14 and boils 

 at 1 1 6. It has a pungent odour and is not rapidly decomposed by water. 



By the action of ammonium carbonate upon benzene sulphonyl chloride 

 benzene sulphonamide is formed : 



C 6 H 6 SO 2 C1 + NH 3 = C 6 H 6 SO 2 NH 2 + HC1. 



Benzene sulphonyl chloride also reacts with aniline and primary amines, 

 secondary amines, but not with tertiary amines : 



C 6 H B SO a Cl + H a N . C 6 H B C 6 H 6 . SO 2 . HN . C 6 H B + HC1 



Benzene sulphonanilide. 

 With alcohols it forms esters : 



CaHjjSO.Cl + C 2 H 8 OH = C 6 H 6 SO 2 . OC 2 H 5 + HC1. 



Phenol. QH 5 OH. 



Phenol is obtained by fusing benzene sulphonic acid with caustic 



potash. 



0" 

 OH 

 + KHS0 8 . 



It is also obtained by the decomposition of diazobenzene (p. 249). 



Preparation. 



Phenol is contained in coal tar and is present in the middle oil 

 fraction. This fraction on cooling deposits crystals of naphthalene, 

 which are filtered off and pressed out. The oil is shaken with caustic 

 soda which dissolves the phenol ; the alkaline layer is separated and 

 treated with sulphuric acid. Phenol separates out as an oil : it is 

 washed with water and distilled. The distillate is separated into pure 

 crystalline phenol and impure liquid phenol. 



Properties. 



Phenol crystallises in colourless prisms which are deliquescent and 

 turn pink on contact with air and light. It melts at 42 and boils at 

 1 82. It has a characteristic smell, is very poisonous and has a marked 

 caustic action upon the skin. It is not easily soluble in water (I part 

 in 15 parts of water), but it dissolves in alcohol and other organic sol- 

 vents. It is volatile with steam. 



Phenol in its constitution is a tertiary alcohol ; on oxidation it is 

 broken down and gives a variety of products. It differs from aliphatic 

 compounds containing hydroxyl groups in having acid properties. It 

 reacts with caustic alkalies but not with carbonates and forms salts 

 which are obtained by evaporating the solution, e.g. potassium phenate, 



