Question

Assertion (A): Glucose gets oxidized to six carbon gluconic acid on reaction with bromine water.
Reason (R): The carbonyl group is absent in the open chain structure of glucose.

• A. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
• B. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
• C. Assertion (A) is true, but Reason (R) is false.
• D. Assertion (A) is false, but Reason (R) is true.

Hint:

Bromine water oxidizes the terminal aldehyde ($-CHO$) of glucose to a carboxylic acid ($-COOH$), proving the aldehyde group exists.

Answer 1

The Correct Option is C

Step 1: Verify the Assertion.
Bromine water is a mild oxidising agent that selectively oxidises aldehydes. The open-chain form of glucose has a free $-CHO$ group at C1. Bromine water converts this to $-COOH$, giving gluconic acid. Assertion (A) is TRUE.
Step 2: Examine the Reason.
Reason (R) states that the carbonyl group is absent in the open-chain structure of glucose. This is INCORRECT. The open-chain structure of glucose specifically shows an aldehyde carbonyl ($-CHO$) at C1.
Step 3: The reaction is evidence FOR the carbonyl.
The fact that glucose reduces bromine water and gives gluconic acid is actually used as experimental evidence to prove the presence of the aldehyde carbonyl group in glucose.
Step 4: Conclusion.
A is true; R is false. This corresponds to option (C).
\[ \boxed{(C)} \]