184 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



Monosaccharides. 

 Diose. Glycollic aldehyde. 



Trioses. Glyceric aldehyde, dihydroxyacetone. 

 Tetroses. Erythreose, threose. 

 Pentoses. Arabinose, xylose, ribose, etc. 

 Hexoses. Glucose, mannose, galactose, etc. 



In this group it is convenient to include d-g\u- 

 cosamine or aminoglucose. 



Fructose, sorbose, etc. 

 Heptoses, etc. 



Disaccharides. 



Sucrose, maltose, lactose. 



Trisaccharides. 



Raffinose. 

 Tetrasaccharides. 



Stachyose. 

 Polysaccharides. 



Starch, cellulose, dextrin, glycogen, inulin. 

 Gums, pectins, pentosans, mannosans, etc. 



THE MONOSACCHARIDES. 

 Diose. 



C 2 OH, 

 Glycollic aldehyde, | which contains a primary alcohol 



CHO 



group and an aldehyde group, is the first member of the series. 

 It is derived, like all the members of the carbohydrate .group, 

 by oxidation of the corresponding dihydric alcohol, glycol. 

 Trioses. 

 Glyceric aldehyde and dihydroxyacetone are obtained from gly- 



CH 2 OH CH 2 OH 



CHOH CO 



CHO CH 2 OH 



cerol by oxidation with sodium hypobromite or hydrogen peroxide in 

 the presence of ferrous sulphate. They contain respectively an aldehyde 

 and ketone group and they are the first examples of an isomeric 

 aldose and a ketose. Glyceric aldehyde contains an asymmetric carbon 

 atom, but the two stereoisomers, d- and /-glycerose, have not yet been 

 separated. 



