PRACTICAL ORGANIC AND filO-CHEMISTRY 



Quinone. 



Quinol is easily oxidised by ferric chloride to quinone, but quinone 

 Is usually prepared by oxidising aniline with potassium bichromate 

 and sulphuric acid. 



It is a yellow crystalline solid with a peculiar smell and melts 

 at 1 1 6. It is not very soluble in water, but dissolves in alcohol and 

 ether. It is volatile in steam. 



Quinone in some respects behaves as a diketone, but in other 

 respects as an aromatic compound : it isi generally represented by the 

 O 



in which there are two pairs of double bonds. On re- 



formula 



/\ 



duction the centric formula is formed, but on oxidation 



it breaks down at the double linkings ; it combines 

 II with 2 or 4 atoms of bromine. 



Reactions of Catechol, Resorcinol^ Quinol. 

 Aqueous solutions behave as follows : 



(1) With FeCl 3 : Catechol gives a green coloration; this colour 

 changes to violet, then to red on adding sodium carbonate or ammonia. 

 Resorcinol gives a deep violet coloration. Quinol on boiling with ferric 

 chloride yields quinone with its peculiar irritating smell. 



(2) With bromine water : Resorcinol gives a crystalline precipitate 

 of tribromoresorcinol. 



(3) Catechol and quinol reduce ammoniacal silver nitrate, 



(4) Catechol and quinol reduce Fehling's solution. 



(5) Solutions of catechol and quinol, made alkaline with caustic 

 soda, turn brown, firstly at the surface but on shaking throughout the 

 whole solution. This is due to absorption of oxygen and oxidation. 



(6) With Millon's reagent : Quinol gives a yellow colour and then 

 a yellow precipitate which becomes red on heating. 



Guaiacol and Veratrol. 



These compounds are' methyl deriva- 



Itives of catechol and are contained in 

 f ^OCHj, natura i substances. Guaiacol, like o- 

 hydroxy-phenols, gives a coloration with 

 ferric chloride ; veratrol gives no colora- 

 tion. 



