CHAP. III.] 



ISOMERS OF LEUCINE. 



243 



Results of l. By heating leucine obtained from proteids with 



HI' a^d i0 HNO f fumin g HI in seajed tubes at from 140 150 C. 

 on leucine. * Hiifner found that there were obtained caproic acid, 

 iodide of ammonium and iodine, according to the 

 following equation : 



C 5 H 10 (NH 2 ) . CO(OH) + SHI = C 6 H n . CO(OH) + NH 4 I + 1 2 . 



Leucine. Caproic acid. 



2. When leucine is dissolved in nitric acid and the solution is 

 treated with nitrous acid, it exhibits the general reaction of the 

 amido-acids, the whole of its nitrogen being resolved in the gaseous 

 form and leucic (or oxy caproic) acid being formed. 



C 6 H U (NH 2 )0 2 + HN0 2 = G 6 H n (OH)0 2 + N 2 + H 2 0. 



Leucic acid 



Leucic acid bears to leucine the same relation which glycollic 

 )id bears to glycocine and lactic acid to alanin. 



The relationship is shewn below : 



Glycocine CH 2 (NH 2 ) . COOH Glycollic acid CH 2 (OH) . COOH. 

 Alanin C 2 H 4 (NH 2 ) . COOH Lactic acid C 2 H 4 (OH) . COOH. 



Leucine C 5 H 10 (NH 2 ) . COOH Leucic acid C 5 H 10 (OH).COOH. 



isomers of Of all the theoretically possible leucines having the 



Leucine. general formula C^H^^NC^, the dextrogyrous leucine 

 z-amido-isobutylacetic acid) is, as already stated, the one formed in 

 e processes of the economy. Allusion has been made to an inactive 

 leucine which is formed under the influence of barium hydrate at 

 high temperatures, and of a laevogyrous leucine which is presumably 

 associated with an exactly equal quantity of the dextrogyrous body, 

 in inactive leucine. These leucines all have the same chemical con- 

 stitution as the normal leucine, being physical isomers of the latter 

 body. The same remark applies, almost certainly, to a leucine 

 described by Nencki. This observer 1 separated, from decomposing 

 pancreas, a leucine which is an isomer of normal leucine, but which 

 differs from it in certain important properties. One part requires 

 43'6 parts of water at 14'5 C. to dissolve it ; its solubility is there- 

 fore about half that of normal leucine. It possesses a feebly sweet 

 taste, and when heated to 210 sublimes without previous melting ; 

 under the action of heat it gives off the odour of amylamine. No 

 details are given as to the optical properties of this leucine. 



1 Nencki, ' Zur Kenntniss der Leucine,' Journ. f. prakt. Chem., N. F. Vol. xv. 

 390398. 



162 



