Q. 13.56 - An Introduction to General, Organic, and Biological Chemistry

Question

 Sophorose, a carbohydrate found in certain types of beans, has the following Haworth structure: 

a. Is sophorose a mono-, di-, or polysaccharide?

b. What are the monosaccharides in sophorose?

c. What is the glycosidic link in sophorose?

d. Is this the $\alpha$ or $\beta$ isomer of sophorose?

e. Is sophorose a reducing sugar?

Step-by-Step Solution

Answer

Saccharides does sophorose falls, mono-, di- or poly-saccharides.

Step 1: Given information (Part-a)

• Sophorose is a carbohydrate found in several types of beans.
•  Looking at the structure of Sophorose we can see that it has only one glycosidic bond (a bond that is formed when the hydroxyl group of one monosaccharide reacts with the hydroxyl group of another monosaccharide). Sophorose is a disaccharide 
• since it possesses one glycosidic link, which means two sugars are joined.

Step 2: Diagram (Part-a)

In this problem, we must determine whether sophorose belongs to the mono-, di-, or polysaccharide groups of saccharides.

Step 3: Given information (part-b)

• Sophorose is a carbohydrate found in several types of beans
•  Its Howarth structure is given in the diagram below.
• 
  

Step 4: Explanation (Part-b)

• Sophorose is a disaccharide made up of two sugars that, upon closer inspection, appear identical. Both sugars contain glucose, however the distinction is in the anomeric carbon (carbon formed from the carbohydrate molecule's carbonyl carbon component's open-chain version).
• $\alpha -$anomer$OH$ is one glucose is the polar opposite of $OH$ ${\mathrm{CH}}_2\mathrm{OH}$ and the other is anomer $\beta$ (OH group on the same side as ${\mathrm{CH}}_2\mathrm{OH}$
  
• 
  

Step 5: Given information (Part-c)

• Sophorose is a carbohydrate found in several types of beans, and its Howarth structure is given in the diagram below.

• We must locate the glycosidic link in sophorose in this scenario.

Step 6: Explanation (Part-c)

• When the hydroxyl group of one monosaccharide combines with the hydroxyl group of another monosaccharide, a glycosidic bond is produced.
• The first hydroxy group of $\beta$-glucose (first $OH$ group on the same side as $C{H}_{2}OH$ interacted with the second hydroxy group of $\alpha -$glucose (first $OH$ group opposite from $C{H}_{2}OH$), resulting in a $\beta -1,2$ glycosi
• 
  

Step 7: Given information (Part-d)

• Sophorose is a carbohydrate found in several types of beans, and its Howarth structure is given in the diagram below.

• In this problem, we must determine if the isomer of sophorose illustrated in Figure 1 is$\alpha$ or $\beta .$
  

Step 8: Explanation (Part-d)

•  This sugar is $\beta$ isomer of Sophorose because it possesses $\beta -1,2$ glycosidic bond (red bond in Figure below), which indicates that anomeric carbon has oxygen on the same side as $C{H}_{2}OH$ group.

Step 9: Given information (Part-e)

• Sophorose is a carbohydrate found in several types of beans, and its Howarth structure is given in the diagram below.

• We must determine whether sophorose is a lowering sugar in this scenario.

Step 10: Explanation (Part-e)

• Reducing sugars are aldehyde-group carbohydrates that can reduce the $C{u}^{2+}$ in Benedict's reagent.
• Every sugar that has an aldehyde group in an open-chain form is a reducing sugar.
• Look for the hemiacetal group (a hemiacetal is a carbon attached to two oxygen atoms, one of which is alcohol ($OH$) and the other is an ether ($OR$) to see which sugar has an aldehyde group in an open-chain form.
• Sophorose has one hemiacetal group, which is the aldehyde group in open-chain form, indicating that it is a reducing sugar.
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