116 Messrs Morrell and Crofts, Modes of Formation of Osones. 



to give osazones points to the intermediate formation of such 

 aldehyde ketone alcohols. The formation of an insoluble hydra- 

 zone of mannose and the transformation of mannose hydrazone by 

 the action of excess of phenylhydrazine into mannosazone, identical 

 with glucosazone, have been explained in the following way : the 

 aldehyde grouping first reacts with phenylhydrazine, and then the 

 excess of phenylhydrazine is enabled, by the withdrawal of two 

 hydrogen atoms from the (CHOH) adjacent to the aldehyde group, 

 to react with the ketone grouping thus formed to give an osazone 

 [E. Fischer, Ber. xx. 821]. 



These ketone aldehyde alcohols (osones) were first prepared by 

 E. Fischer, who removed from the corresponding osazones the two 

 phenylhydrazine residues by careful treatment with concentrated 

 hydrochloric acid [Ber. XXII. 87], 



CH— N— NHC 6 H 5 . CHO 



I I 



C_ N— NHC 6 H 5 . — CO 



i I 



(CHOH) 3 (CHOH) 3 



CH 2 OH. CH 2 OH. 



phenylglucosazone. glucosone. 



The yield of osone was good, if small quantities of the osazones 

 were used. The isolation of pure glucosone was troublesome, since 

 the osone had to be precipitated from solution by means of lead 

 hydroxide, with which it formed a loose chemical compound. This 

 method has not yielded the glucosone in a crystalline form, but only 

 as a syrup. The characteristic properties of the osones were their 

 strong reducing action on Fehling's solution, the readiness with 

 which they reacted with phenylhydrazine at the ordinary tempera- 

 ture and the ease with which they were transformed into furfurol 

 on being heated with water at 130°C. By this method the follow- 

 ing sugars were transformed into corresponding osones : d glucose, 

 galactose, and rhamnose [E. Fischer, Ber. xxn. 96]. Glucosone, 

 obtained from phenylglucosazone, when reduced by zinc dust, was 

 transformed into d fructose. This shewed that the aldehyde 

 grouping of the osone is reducible to the primary alcoholic group 

 CH 2 OH [E. Fischer, Ber. xx. 94]. 



In 1902, E. Fischer [Ber. xxxv. 3141] obtained osones from 

 the more soluble osazones of the disaccharides by means of 

 Herzfeld's method, whereby the phenylhydrazine residue of a 

 hydrazone was removed by benzaldehyde. Benzaldehyde and 

 an osazone reacted to form benzaldehyde hydrazone and the 

 corresponding osone. 



2 C 6 H B CHO + C 24 H 32 N 4 9 = C 12 H 20 O u + 2 [C 6 H 5 CH-N— NHC 6 H 6 ] 



maltosazone. maltosone. 



