Give three reactions of glucose which cannot be explained by its open chain structure.

Explanation

To answer the question regarding three reactions of glucose that cannot be explained by its open-chain structure, we will explore the unique properties of glucose in its cyclic form. Here is a step-by-step solution:

### Step 1: Understanding Glucose Structure
Glucose can exist in two forms: an open-chain (linear) structure and a cyclic structure (pyranose form). The cyclic form is more stable and predominant in solution.

### Step 2: Reaction 1 - 2,4-Dinitrophenylhydrazine (2,4-DNP) Test
- **Observation**: Glucose does not give a positive 2,4-DNP test.
- **Explanation**: The 2,4-DNP test is used to detect carbonyl groups (aldehydes and ketones). In the open-chain form, glucose has an aldehyde group, which would react with 2,4-DNP. However, in its cyclic form, the carbonyl group is involved in the formation of the hemiacetal, thus preventing the reaction.
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