ORGANIC CHEMISTRY. 



R-CHOH'CHO + H 2 N NH'C 6 H 5 = 



A Idose (aldehyde sugar). Phenyl hydrazine. 



R-CHOH'CH : N NHC 6 H 5 + H 2 O 



Phenyl hydrazone. 



R-CHOH'CH : N NH'C 6 H 5 + H 2 N NTiC 6 H 5 



Phenyl hydrazone. Phenyl hydrazine. 



RCO-CH : NHNHC 6 H 6 + 



Ketone of phenyl hydrazine. 



H 2 NC 6 H 5 +NH 3 



Aniline Ammonia Water. 



R-COCH : N'NHC 6 H 6 + H 2 N NH'C 6 H 6 = 



Ketone of phenyl hydrazone. Phenyl hydrazine 



RC ( : N-NHC 6 H 5 ) CH : N'NHC 6 H 5 + H 2 O 



Phenylosazone. Water. 



Fischer found these compounds extremely useful in isolating 

 the various sugars, because they are relatively insoluble and 

 crystallise well.* The crystals are yellow in colour, and they 

 can be identified by their shape and melting point. Substituted 

 phenyl hydrazines are used for special purposes. f 



Seliwanoff Reaction. % On heating ketone sugars in a 

 solution containing 18 per cent, of hydrochloric acid (equal 

 parts of concentrated hydrochloric acid and sugar solution) 

 a red colour is given, but the addition of resorcinol gives a 

 deeper red colour and later on a red precipitate which 

 dissolves in alcohol to form a red solution. This test is used 

 for the identification of fructose and sucrose (cane sugar) . 



Pentose Tests. On heating a sugar containing an odd 

 number of carbon atoms with 18 per cent, hydrochloric acid 

 and phloroglucinol or orcinol, a cherry red colour is produced 

 with the former and a violet followed by blue green or blue 

 with the latter, both of which become precipitated on standing. 



These coloured condensation products can be dissolved in 

 amyl alcohol, and their solutions examined spectroscopically . 

 The phloroglucinol product shows an absorption band between 

 D and E, and the orcinol product one between C and D, but 

 near to D. 



Mucic Acid Test. On oxidising galactose (and lactose) 

 with nitric acid a crystalline product (m.p. 213 C.) is easily 

 separated. This is mucic acid, and serves to identify galactose 

 in its compounds. 



* E. Fischer, Ber., 1884, vol. 17, pp. 572 and 579. 

 f C. Neuberg and H. Strauss, Zeitschr. f.physiol. Chem., 1902, vol. 36, 

 p. 227. 



J T. Seliwanolf, Ber., 1887, vol. 20, p. 181. 



H. J. Wheeler and B. Tollens, Ber., 1889, vol. 22, p. 1046. 



