Which of the following pair gives same phenyl osazone ?

Options

A. D-Glucose and D-Allose
B. D-Glucose and D-Alfrose
C. D-Glucose and D-Mannose
D. D-Glucose and D-Talose

Explanation

To determine which pair of sugars gives the same phenyl osazone, we need to analyze the structures of the sugars involved and how they react to form phenyl osazone. Here’s a step-by-step solution:

### Step 1: Understand the concept of phenyl osazone formation
Phenyl osazones are formed when sugars react with phenylhydrazine. The reaction involves the carbonyl group (C=O) of the sugar, which reacts with phenylhydrazine to form a hydrazone, and subsequently, a phenyl osazone.

### Step 2: Identify the sugars in the options
The options provided are:
1. D-glucose and D-fructose
2. D-glucose and D-alfrose
3. D-glucose and D-mannose
4. D-glucose and D-talose

### Step 3: Analyze the structures of the sugars
- **D-glucose**: An aldohexose with the structure where the carbonyl group is at the first carbon.
- **D-mannose**: An aldohexose that differs from glucose only at the second carbon (the configuration of OH and H is reversed).
- **D-talose**: An aldohexose that differs from glucose at the fourth carbon.
- **D-alfrose**: An aldohexose that differs from glucose at the second carbon.

### Step 4: Compare the structures of D-glucose and D-mannose
D-glucose and D-mannose differ only in the configuration at the second carbon. When both sugars react with phenylhydrazine, the resulting phenyl osazone will have the same structure because the configuration at the second carbon does not affect the formation of the double bond in the osazone structure.

### Step 5: Conclusion
Since D-glucose and D-mannose yield the same phenyl osazone structure, the correct answer is:
**D-glucose and D-mannose.**