540 CONSIDERATION OF CARBON COMPOUNDS. 



Nitric or nitrous acid may combine with organic bases, forming 

 salts, such as strychnine nitrate, urea nitrate, etc. ; or with alcohols 

 when esters result, such as glyceryl nitrate, ethyl nitrite, etc. Some 

 of these compounds have been considered before. 



Nitro compounds. These consist of radicals in combination with the 

 nitric acid residue N0 2 ; thus, R.NO 2 . They are isomeric with the esters of 

 nitrous acid, but behave quite differently from these; for instance, they yield 

 no alkali nitrite when treated with alkalies, as is the case when esters are thus 

 treated. The difference in structure is represented thus : 



K O NO, R NO 2 , 



Nitrite. Nitro compound. 



The highly important nitro compounds of the benzene series can be 

 obtained by treating the hydrocarbons directly with nitric acid; thus: 



C 6 H 6 + HON0 2 = C 6 H 5 N0 2 + H 2 O. 



Nitric acid does not react with fatty hydrocarbons, but their nitro deriva- 

 tives can be obtained by indirect processes, for instance, by treating the halo- 

 gen derivatives with silver nitrite: 



CH 3 C1 + AgNO 2 r= CH 3 N0 2 - + AgCl 

 Methyl chloride. Nitro-me thane. 



This reaction is anomalous, since we would expect to obtain a true ester of 

 nitrous acid, corresponding to silver nitrite, whereas the resulting product is 

 not an ester, but a uitro compound. A rearrangement takes place during the 

 reaction of the two substances on each other. Other cases of this kind are 

 known, for example, the formation of organic isocyanides (which see) from 

 silver cyanide. 



Nitroso and isonitroso compounds. While compounds containing the 

 group NO 2 are called nitro compounds, those containing the group NO are 

 termed nitroso derivatives, and those containing = N OH are known as iso- 

 nitroso derivatives. 



When a compound containing the group = CH is treated with nitrous acid 

 a reaction takes place which results in the formation of a nitroso compound, 

 thus : 



E 3 .CH + HNO 2 R 3 .C.NO + H 2 O. 



Nitroso compound. 



Isonitroso compounds are formed by the action of hydroxylamine on alde- 

 hydes or ketones : 



H 2 NOH + >CO = ^>C = N OH + H 2 O. 



Hydroxylamine. Ketone. Isonitroso compound. 



Isonitroso compounds are isomeric with nitroso compounds; the different 

 linkage of carbon and nitrogen in the two classes of compounds is indicated in 

 the two equations given above. 



Both nitro and nitroso compounds, when treated with nascent hydrogen, 

 yield ammonia derivatives, as will be shown later. Isonitroso compounds are 



