Question

Match items of Row I with those of Row II:

 

[(i)] $\alpha$-D-(-)-Fructofuranose 
[(ii)] $\beta$-D-(-)-Fructofuranose 
[(iii)] $\alpha$-D-(+)-Glucopyranose 
[(iv)] $\beta$-D-(+)-Glucopyranose 
Correct Match:

• A. $P \rightarrow$ iv, $Q \rightarrow$ iii, $R \rightarrow$ i., $S \rightarrow ii$
• B. $P \rightarrow$ iii, $Q \rightarrow$ iv, $R \rightarrow$ i., $S \rightarrow ii$
• C. $P \rightarrow$ iii, $Q \rightarrow$ iv, $R \rightarrow$ ii., $S \rightarrow i$
• D. $P \rightarrow$ i, $Q \rightarrow$ ii, $R \rightarrow$ iii., $S \rightarrow iv$

Answer 1

The Correct Option is B

- (P): $\alpha$-D-(+)-Glucopyranose (iii): This structure has the -OH group at C1 in the $\alpha$-position (below the plane) in the six-membered pyranose ring.
- (Q): $\beta$-D-(+)-Glucopyranose (iv): This structure has the -OH group at C1 in the $\beta$-position (above the plane) in the six-membered pyranose ring.
- (R): $\alpha$-D-(-)-Fructofuranose (i): This structure is a five-membered fructofuranose ring with the $\alpha$-configuration (OH group at C2 below the plane).
- (S): $\beta$-D-(-)-Fructofuranose (ii): This structure is a five-membered fructofuranose ring with the $\beta$-configuration (OH group at C2 above the plane).
Thus, the correct matching is: \[ \text{P $\to$ iii, Q $\to$ iv, R $\to$ i, S $\to$ ii.} \] 1. Glucose exists in both pyranose ($\text{six-membered}$) and furanose ($\text{five-membered}$) forms. Pyranose forms are more stable.
2. $\alpha$ and $\beta$ forms differ in the configuration of the hydroxyl group at the anomeric carbon (C1 for glucose and C2 for fructose).
3. Fructose predominantly forms five-membered furanose rings due to its keto group.