238 SYNTHESIS AND CONSTITUTION OF LEUCINE. [BOOK II. 



It was until lately surmised, mainly in consequence of the 

 researches of Hufner 1 , that the first of the two formulae represented 

 the constitution of the leucine of the animal body. 



Schulze 2 having proved that the leucine which is obtained by 

 the decomposition of vegetable proteids has the constitution of 

 amido-isobutylacetic acid, Hufner has lately caused a most elaborate 

 investigation to be made in his laboratory by Dr Bernhard Gmelin 3 , 

 who has conclusively shewn that leucine of animal origin possesses 

 the same constitution as that derived from vegetable proteids, and 

 that the variations which leucine presents in physical characters 

 as, for example, in solubility and in its power of rotating the plane 

 of polarization according to the conditions under which it is formed, 

 are explicable on the theory of physical isomerism, the chemical 

 constitution being the same. 



Synthesis of In a large flask, furnished with an inverted con- 



leucine by the d enser 125 grins, of potassium bichromate are heated 



action of HC1 . , t -ton f u j i v 



and HCN on WJ th a mixture or loo grms. ot concentrated sulphuric 



vaieraidehyde acid and 1250 c.c. of water to a temperature of 90. 

 ammonia Through a stoppered funnel 100 grms. of amyl alcohol 



(Limpricht). are then allowed to flow in gradually. In this reaction 

 valeric aldehyde (C 4 H 9 . COH) is formed. This body is now sepa- 

 rated by distillation ; the distillate is first of all shaken with a dilute 

 solution of sodium hydrate, which is then got rid of by means of a 

 separating funnel, and the impure vaieraidehyde is shaken with a 

 concentrated solution of acid sodium sulphite (sodium bisulphite, 

 NaHSO 3 ). Crystals of valeraldehyde-sodium sulphite separate : 



O OH 



C 4 H 9 (/ +NaHS0 2 = C 4 H 9 CH 



_ X NaS0 3 . 



Sodium Valeraldehyde-sodium 



Bisulphite Sulphite. 



The crystals are filtered, pressed between filtering paper, and 

 distilled with solution of sodium hydrate, when vaieraidehyde is set 

 free and distils over. The distillate is treated with concentrated 

 ammonia and thoroughly shaken, when valeraldehyde-ammonia 

 separates out in the crystalline form. 



1 Hufner, Journal fur pr. Chemie (2), 1, 6 ; Zeitschrift /. Chem., Ser. 2, Vol. iv. 

 (1868), p. 391 and 616. 



2 Schulze u. Likiernik, Ueber die Constitution des Leucins.' Ber. d. d. ch. 

 Gesellsch., Bd. xxiv. (1891), 4, 669. 



3 Bernhard Gmelin, 'Beitrage zur Kenntniss des Leucins' (Inaugural-Dissertation, 

 Tubingen, 1892). 



