46 



CARBOHYDRATES AND THEIR 



[CH. 



the hydrolysis of cane-sugar and maltose, and, in all probability, is the 

 first sugar synthesized from carbon dioxide and water. Its synthesis and 

 its relationships to other sugars will be discussed later (see p. 69). It is 

 a white crystalline substance, readily soluble in water and aqueous 

 alcohol, but only slightly soluble in absolute alcohol. 



If, as in the case of a pentose, we examine the structural formula for 



a hexose, such as glucose : 



H C = O 



H C* OH 

 HO C* H 

 H C* OH 

 H C* 



OH 



H C H 

 OH 



we see that there are four carbon atoms marked * which are united 

 to four different groups of atoms. It will be found in this case that there 

 are sixteen possible isomers : 



CHO 



H C OH 

 H C OH 



HO C H 

 HO C H 



CH 2 OH 

 -Mannose 



CHO 



HO C H 

 HO C H 

 H C OH 

 H C 



OH 



CH 2 OH 



d-Mannose 



CHO 



HO C H 



HO C H 



HO- 



CH. 2 OH 



^-Glucose 



H C OH 



CH 2 OH 



rf-Glucose 



CHO 



HO C H 



H C OH 

 HO C H 



H C OH 



CH 2 OH 

 2-Idose 



CHO 

 H C OH 



HO C H 



I 

 H C OH 



HO C H 

 CHOH 



CH 2 OH 



Z-Gulose 



I 

 CHO 



I 

 HO C H 



HO C H 



H C OH 



j 

 HO C H 



CH 2 OH 



rf-Gulose 



