SUCROSE 113 



Constitution. 



Whilst it has long been known that sucrose on hydrolysis 

 yields molecular proportions of glucose and fructose, it was 

 first shown by Irvine and Steele * that the fructose occurred 

 in the y-form and not in its normal form in combination with 

 glucose. 



The constitutional formula f for cane sugar, based on the 

 amylene oxide formula for the glucose constituent and the 

 butylene oxide formula for the y-fructose, is as follows : — 



XH o- 



CH^OH 



I 



O (CHOH)3 (CHOH)., O 

 I CH CH 1 



I I 



CHjOH CH2OH 



Glucose y-Fructose 



Repeated attempts to synthesize cane sugar from glucose 

 and fructose failed owing to the fact that the fructose requires 

 to be combined with the glucose in its active or y-form. 



Appreciating this fact, Pictet and Vogel | prepared the 

 acetyl derivative of y-fructose, and uniting this with the acetyl 

 derivative of glucose, by shaking the two in chloroform 

 solution with phosphorus pentoxide, they obtained octacetyl 

 sucrose which on hydrolysis yielded a compound showing all 

 the characteristics of the natural sucrose. 



Properties. 



Cane sugar crystallizes from water in monoclinic crystals 

 which do not contain water of crystallization ; it is readily 

 soluble in water and only slightly soluble in alcohol ; it is 

 dextro-rotatory, its specific rotation being a^ =+ 66-5. 



When heated to 160° it melts to a glassy mass known as 

 barley sugar, which gradually becomes crystalline again ; if 

 heated to 190-200° it is converted into an uncrystallizable 



* Irvine and Steele : " J. Chem. Soc," 1920, 117, 1474. 

 t Haworth and Hirst : id., 1926, 1858. Avery, Haworth, and Hirst : 

 id., igz'j, 2308. 



t Pictet and Vogel : " Compt. rend.," 1928, 186, 727. 



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