Question

Three structures are given below in which two glucose units are linked. Which of these linkages between glucose units are between $C1$ and $C4$ and which linkages are between $C1$ and $C6$?

• A. (a) and (c) are between $C1$ and $C4$, (b) is between $C1$ and $C6$
• B. (a) is between $C1$ and $C4$, (b) and (c) are between $C1$ and $C6$
• C. (a) and (c) are between $C1$ and $C6$, (b) is between $C1$ and $C4$
  
• D. (a) and (b) are between $C1$ and $C4$, (c) is between $C1$ and $C6$

Answer 1

The correct option is A (a) and (c) are between $C1$ and $C4$, (b) is between $C1$ and $C6$

In general, in a cyclic saccharide structure the carbon making the acetal or hemiacetal group is numbered as $1$. Such carbon is bonded with oxygen atoms. It is also called as the anomeric carbon

i) In structure $I,C1$ of one glucose is linked with $C4$ of other glucose. So, linkage (a) is between $C1$ and $C4$.

ii) In structure $II,C1$ of one glucose is linked with $C6$ of other glucose. So, linkage (b) is between $C1$ and $C6$.

In structure $III,C1$ of one glucose is linked with $C4$ of other glucose. So, linkage (c) is between $C1$ and $C4$.

So, the correct answer is option (C).