H4 Biological Chemistry. 



CH 3 CH 3 



ii 



CH 2 OH 



the ordinary fermentation amyl alcohol. 



Thus, by a comparatively simple laboratory process, 

 the constitution of an important biological product can be 

 ascertained. 



.Besides ethyl malonate, other substances can be em- 

 ployed for the purpose of analogous synthetical reaction. 

 The most important of these is perhaps the substance 

 known as acetoacetic ether, or ethyl acetoacetate 



CH 3 .COCH 2 .CO-OC 2 H 5 * 



This again contains a CH 2 group between two car- 

 bonyl groups, and has consequently two hydrogen atoms 

 replaceable by sodium. The syntheses of this substance 

 are more complex and need not be considered in greater 

 detail in this place. 



Succinic acid 



CH 2 COOH 



Ji 



)H 2 COOH 



This acid occurs in many plants, in certain animal secretions, 

 and in amber. It is also a by-product of the alcoholic fer- 

 mentation of sugar. Its constitution is readily determined 

 by a simple synthesis. When dibromethane is treated 

 with potassium cyanide, the corresponding cyano derivative 

 is obtained, which on hydrolysis yields succinic acid 



* This substance is an equilibrated mixture of two isomeridea 



CH 8 ' CO CH 2 ' COOC 2 H 5 ^ CH 3 C(OH)=CH COOC 2 H 5 



The former is called the ketonic and the latter the enolic form. Such isomerides 

 which readily pass from one into another are said to be tautomeric or des- 

 motropic forms. 



