AROMATIC COMPOUNDS 265 



/OH 

 Saligenin, or Salicylic Alcohol, C 6 H 4 \ 



CH 2 OH. 



Saligenin occurs as the glucoside, salicin, in the bark of the willow 

 tree. The glucoside, on hydrolysis, gives glucose and saligenin. 



It is generally prepared by reducing salicylic aldehyde with 

 sodium amalgam and dilute alcohol. 



Saligenin is a crystalline solid which melts at 82 and is easily 

 soluble in water. It is o-hydroxy-benzyl alcohol. 



As it contains a phenolic group in the a-position it gives a blue- 

 violet colour with ferric chloride. It forms alkali salts with alkaline 

 hydroxides and behaves like a phenol. It also behaves like a primary 

 aliphatic alcohol and is converted on oxidation into salicylic aldehyde 

 and salicylic acid. 



/OH 

 Salicylic Aldehyde, CH 4 < 



X CHO. 



o-Salicylic aldehyde is found in certain volatile oils from plants. 



It can be prepared by oxidising saligenin with potassium bichro- 

 mate and sulphuric acid. 



It is generally prepared by Reimer's reaction : a mixture of phenol, 

 chloroform and caustic potash is heated under a reflux condenser : 

 C 6 H 5 OH + CHC1 3 + 4 KOH = C 8 H 4 (OK)CHO + 3 KC1 + 3 H 2 O. 



The solution is acidified after distilling off the chloroform and distilled 

 with steam ; phenol and o-salicylic aldehyde pass over. The distillate 

 is extracted with ether and the aldehyde converted into the bisulphite 

 compound ; this is decomposed with sodium carbonate, the salicylalde- 

 hyde extracted with ether and distilled. 



p-Hydroxybenzaldehyde is also formed in the reaction, but is not 

 volatile with steam. 



Salicylic aldehyde is an oily liquid boiling at 196 with characteristic 

 aromatic smell : it gives a violet colour with ferric chloride. 



/OH 



Salicylic Acids, C 6 H / 



The chief of the hydroxy-benzoic acids is the o-compound or sali- 

 cylic acid, which occurs in the flowers of Spircea ulmaria and in the 

 form of its methyl ester in oil of winter green. 



Salicylic acid was formerly prepared (i) by the hydrolysis of oil of 

 winter green ; (2) by oxidising salicylic alcohol ; (3) by the action of 

 nitrous acid on anthranilic acid. 



