CYANOGEN COMPOUNDS 161 



A m mon in m Cya na te. 



Ammonium cyanate is prepared by bringing cyanic acid into contact with 

 dry ammonia. 



It is a white crystalline powder soluble in water ; the aqueous solution 

 on evaporation yields urea (p. 131). 



The salts of cyanic acid with the heavy metals are insoluble and are 

 formed from potassium cyanate by double decomposition. 



Cyanuric Acid. H 3 O 3 C 3 N 3 . 

 Cyanuric acid has probably the constitution, 



C.OH 



/\ 

 1 



HO.C C.OH, 



\/ 



N 



and is prepared from urea : 



(1) by heating it (p. 133); 



(2) by passing chlorine over it at 130-140 ; 



(3) by heating it with a solution of carbonyl chloride in toluene at 190-230. 



3 CO(NH 2 ) 2 = 3 NH 



Cyanuric acid crystallises from water with 2 molecules of water of 

 crystallisation in large rhombic prisms. It is soluble in 40 parts of cold 

 water, more easily in hot water and alcohol. It is decomposed by boiling 

 with acids into carbon dioxide and ammonia. 



It is a tribasic acid forming soluble salts with the alkali metals and in- 

 soluble salts with the heavy metals; the copper salt is violet in colour. 



Alkyl Isocyanates and Alkyl Cyanates. 



Alkyl isocyanates are formed on heating silver cyanate with an alky 

 iodide : 



AgNCO + CH 3 I = CH 3 NCO + Agl. 



These compounds are also obtained when potassium cyanate is distilled 

 with alkyl potassium sulphate : 



KOCN + CH 3 O . SO 2 . OK = CH 3 . NCO + KO . SO 2 . OK. 



A rearrangement of the atoms of the molecule has occurred on heating. 



The alkyl isocyanates are volatile liquids with a strong, disagreeable, 

 suffocating odour. They boil without decomposition and are soluble in ether. 

 They polymerise on standing forming isocyanuric esters. 



Their structure is shown by their conversion into amines by the action of 

 potash : 



CH 3 . NCO + H 2 = CH 3 . NH 2 + CO 2 . 



The alkyl cyanates are obtained by the action of cyanogen chloride on 

 sodium alkoxide : 



C1CN + NaOCH 3 = CH 3 OCN + NaCl. 



They are colourless ethereal liquids, which at once polymerise to cyanur- 

 ates. 



Alkyl cyanurates are obtained from sodium alkoxide and cyanuric chloride 



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