PROXIMATE CONSTITUENTS OF THE ANIMAL BODY 49 



^ 105 alC f rmed ^ the replacement of or * H ^m by the group OK 

 CH 3 



I 

 CHOH is oxypropionic acid or lactic acid. 



COOH 



KETO- ACIDS. Oxyacids are formed by the oxidation of the group CH 2 or < II 

 If at the same time the H 2 group be removed by oxidation a keto-acid may be formed! 

 This is probably the manner in which such acids arise in the body, though it is 

 usual to regard a keto-acid as the result of oxidation of a ketone. * Thus : 



more 



CH< 



CH 



OH 3 



CO 



CH 3 



(acetone) 



CO 



da 



UJj.a . 



OH 



COOH 



(pyruvic acid 

 a keto-acid) 



ACID AMIDES are formed from a fatty acid by replacing the - OH of the - MIMH 

 group by NH 2 , e.g. : 



CH 3 CH 3 



from 



CO.NH 2 COOH. 



(acetamide) (acetic acid) 



AMINES. These may be regarded as formed from ammonia NH 3 by replacing 

 one or more of the H atoms by an organic radical. Thus we may have : 



CH 



(methylamine) 



/CH 3 

 NeCH 3 

 X H 



(dimethylamine) 



/CH 3 

 Ne-CH, 



X CH 3 



(trimethylamine) 



Under the action of living organisms primary amines may be formed from a-amino 

 acids by a process of decarboxylation. Thus : 



CH 3 CH 3 



CH.NH 2 - C0 2 = CH 2 .NH 2 



CO 



)OH 



(a-amino-propionic acid) 



(ethylamine) 



AROMATIC COMPOUNDS 



These all contain a nucleus, made up of six carbon atoms, which is extremely stable, 

 so that processes of oxidation, reduction, Ac., can be carried out i 

 without destruction of the nucleus. The simplest aromatic compound 

 C 6 H 6 . It behaves as a saturated compound. It is represented as a h 

 hydrogen atom at each angle. 



/> 



Hl/H 



H 



