i PRIMARY DISSOCIATION-PRODUCTS 33 



their derivatives, and converted them into one another. Active leucin is 

 very readily racemised, 1 and E. Fischer has therefore recommended to 

 convert all the leucin straight away into the racemised variety, 

 especially as the raceme -compounds are less soluble. The melting- 

 point of all three leucins is 293-295 ; they undergo decomposition on 

 melting. Leucin-imide (see below) is a derivative of leucin. 



4 (b). Iso-leucin, C 6 H 13 N0 2 is probably a /2-amino-caproic acid. 



This naturally occurring isomer of leucin has been discovered by 



Felix Ehrlich. 2 While leucin in water is Isevo-rotatory, iso-leucin in 



-~ atery, acid, and alkaline solutions is dextro-rotatory ; in 20 per cent 



IC1 compared with leucin, it is twice as strongly dextro-rotatory than 



in leucin, iso-leucin shows the following amounts of rotation, in 



water 20 p.c. HC1 in alkaline solution 

 D +9-74 +36-80 +11-1 



Iso-leucin is very widely distributed throughout the animal and 



vegetable kingdom, occurring everywhere where leucin is found, e.g. 



in blood fibrin and in molasses. It has a bitter taste, and is therefore 



. | an a-amino-acid ; it forms a well-defined compound with phenyl- 



.antoin, and must therefore be a /2-amino-acid, as phenylhydantoin 

 _ily reacts with a and /3 acids. 



Iso-leucin can only be separated from leucin by conversion into a 

 coppersalt as fully explained by F. Ehrlich. 



Cohnheim believes that leucin probably does not stand in direct 

 relationship to the carbo-hydrates as held by Kossel, 3 Fr. Miiller, 4 

 and E. Fischer, 5 and this view is shared by Halsey. 6 



Leucin-imide, C 12 H 22 N 2 2 



may be a primary product, but as there is some doubt it has been 

 described amongst the secondary dissociation products on p. 85. 

 5. Serin, C 3 H 7 N0 3 , is a-amino-/3-hydroxy-propionic acid. 



H NH 2 .0 



HO-C C (T 



H H X OH. 



1 E. Fischer, Ber. d. deutsch. chem. Ges. 33. II. 2370 (1900). 



2 Felix Ehrlich, ibid. 37- 1809 (1904). 3 A. Kossel, ibid. 25. 165 (1898). 



4 Pr. Miiller, Zeitschr.f. Biolog. 42. 468 (1901). 



5 E. Fischer and E. AMerhalden, Zeitschr. f. physiol. Chem. 36. 268 (1902). 



6 J. T. Halsey, Amer. Journ. of Physiol. 1O. 229 (1904). 



D 



