212 Biological Chemistry. 



shown that sugars could be obtained by a somewhat 

 different synthetical process. It was found that acrolein 

 dibromide, CH 2 Br-CHBr-CHO, on treatment with baryta 

 water, yields a mixture of two sugars, which were isolated 

 in the form of their osazones. The reaction representing 

 the formation of these sugars may be represented in the 

 following way 



2C 3 H 4 OBr 2 + 2Ba(OH) 2 = C 6 H 12 6 + 2BaBr 



The sugars isolated were designated a and ft acrose, and 

 were, as might be expected from the fact that they were 

 produced synthetically by ordinary laboratory methods, 

 optically inactive. One of these sugars (the a -variety) 

 was investigated in some detail. From the osazone the 

 osone (see p. 197) was prepared, which on reduction yielded 

 an optically inactive fructose, which would be expected to 

 be a ketone (loc. cit). The optical inactivity is due to 

 the fact that the fructose thus obtained is a mixture of 

 enantiomorphically related pairs. On fermenting with 

 yeast only the cZ-form is consumed, and ^-fructose is left 

 almost untouched by the micro-organism. (Note biological 

 difference between the two stereoisomerides.) From the 

 active fructose, by a somewhat complex series of reactions, 

 several isomeric hexoses were obtained. 



Alcoholic Fermentation of the Sugars. Under the 

 influence of yeast plants, certain sugars undergo a chemical 

 change, which results in the production of alcohol and 

 carbon dioxide. This action, which has long been known 

 as fermentation, is directly due to the presence in the 

 organism of certain substances known as ferments, to the 

 discussion of which part of a later chapter (Chapter VI.) 

 is devoted. The reaction, in the case of dextrose, may be 

 represented by the equation - 



