542 CONSIDERATION OF CARBON COMPOUNDS. 



a small number of organic bases is found in the animal system, 

 urea being the most important one. In plants organic bases are 

 frequently met with, and are grouped together under the name of 

 alkaloids. While the constitution of many alkaloids has not yet 

 been sufficiently explained, we know that many of them are deriv- 

 atives of aromatic compounds, for which reason the consideration of 

 the whole group will be deferred until benzene and its derivatives 

 are spoken of. The large number of basic substances found in putre- 

 fying matter and termed ptomaines will also be considered later on. 



^xll /G%H / xC 2 H 5 / /C 2 H 5 /C H 3 



\ TT \ rT \ TT \O TT \/^ TT 



U2-tL 5 ^4*19 



Or 



NH 3 , N(C 2 H 5 )FT 2) N(C 2 H 5 ) 2 H, N(C 2 H 5 V NCH 3 .C 2 H 5 C 4 H 9 . 



Ammonia. Ethylamine. Diethylamine. Triethylamine. Methyl-ethyl-butylamine. 



The above formulas show that by replacement of either 1, 2, or 3 

 hydrogen atoms, mono-, di-, or tri-amines are obtained. These are 

 also sometimes designated as primary, secondary, and tertiary amines, 

 respectively. Primary ajnines may also be considered as hydrocar- 

 bons, with one hydrogen atom replaced by the radical NH 2 , which is 

 called the amine- or amino-group, and compounds containing it are 

 designated as amino compounds. Thus, CH 3 NH 2 is amino-methane, 

 or methyl-amine. The radical NH is known as the imine- or imino- 

 group, and as this group occurs in secondary amines, these are also 

 termed imino compounds. 



Amines resemble ammonia in their chemical properties ; they are, 

 like ammonia, basic substances; they combine with acids, directly 

 and without elimination of water, thus : 



NH 3 + HC1 = NH 4 C1; 



N(C 2 H 5 ) 3 + HC1 = N(C 2 H 5 ) 3 HC1. 

 Triethylamine. Triethylamine 



chloride. 



The methyl amines are gases at ordinary temperature; the ethyl amines are 

 liquids. Many of them are inflammable ; they have a strong ammoniacal, 

 fishy odor, are readily soluble in water, have strong basic properties (some of 

 them more so than ammonia), and precipitate metallic salts like ammonia. 



The most important reaction of primary amines is that taking place with 

 nitrous acid, thus : 



CH 3 NH 2 + HONO = CH 3 NH 3 ONO = CH 3 OH + H 2 O + 2N. 



Methyl Nitrous Methyl 



amine. acid. alcohol. 



The reaction shows the possibility of replacing the amino group, NH 2 , by 

 hydroxyl, which in this way may be introduced into various compounds. The 



