Which one of the following has no free aldehyde or ketone group ?

Options

A. Fructose
B. Maltose
C. Sucrose
D. Galactose

Answer

To determine which of the following has no free aldehyde or ketone group, we need to understand the difference between reducing and non-reducing sugars.

### Step-by-Step Solution:

1. **Identify Sugar Types**:
- Sugars can be classified into two main categories: reducing sugars and non-reducing sugars.
- Reducing sugars contain free aldehyde or ketone groups, which can participate in redox reactions.

2. **Characteristics of Reducing Sugars**:
- Examples of reducing sugars include fructose, maltose, and galactose.
- These sugars have free aldehyde or ketone groups in their molecular structure.

3. **Characteristics of Non-Reducing Sugars**:
- Non-reducing sugars do not have free aldehyde or ketone groups.
- An example of a non-reducing sugar is sucrose.

4. **Conclusion**:
- Since sucrose is a non-reducing sugar, it does not have any free aldehyde or ketone groups.
- Therefore, the correct answer to the question is **sucrose**.

### Final Answer:
**Sucrose has no free aldehyde or ketone group.**

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