232 A. T. RIXGER AXD EMIL J. BAUMAXN 



Lobry de Bniyn isolated anotlier hexosc, glutose, as a product of the 

 action of alkali on glucose. Glutose is formed through the intermediate 

 stage of a second enolic form derived from fructose, thus : 



CHoOH CII 2 OH CH 2 OH 



I I I 



co con CIIOH 



I II I 



HOCH COH CO 



I : ^ I i * I 



HCOH HCOH HCOH 



I I I 



HCOH HCOH HCOH 



I I I 



CH 2 OH CH 2 OH CH 2 OH 



Fructose Enol Form Glutose 



d-Galactose behaves similarly to d-glucose when treated with dilute alkalis. 

 An equilibrium ensues between it and d-talose, d-tagatose and 1-sorbose. 



Reactions of sugars with Substituted Hydrazines. One of the most 

 important reactions in sugar chemistry for identification of sugars is 

 that which takes place when aldoses or ketoses are heated with an excess 

 of phenylhydrazine in dilute acetic acid. Quite insoluble definite crystal- 

 line compounds are formed, called hydrazones and osazones, which are 

 readily identified by their crystalline structure, melting point, etc. These 

 osazones (and hydrazoiies) were the compounds that enabled E. Fischer to 

 elucidate the chemistry of the sugars. 



The reaction takes place in two stages. In the first, which goes on at 

 20 C., a hydrazone is formed. 



/o 



C CH:N.NH C 6 H 6 



I\H I 



HCOII HCOH 



I I 



HOCH + Coir.jNH.KH, HOCH + H 2 O 



! I 



HCOH > IICOH 



HCOH HCOH 



CH 2 OH CH 2 OH 



Aldose Phenylhydrazine Phenvlhydrazone 

 (Glucose) 



An excess of phenylhydrazine (which should be present) then acts as an 

 oxidizing agent, forming a carbonyl group (CO) from a CTTOH group, 



