Identify the non - reducing sugar.

Options

A.
B.
C.
D.

Answer

To identify the non-reducing sugar, we need to understand the characteristics of reducing and non-reducing sugars.

### Step-by-Step Solution:

1. **Definition of Reducing Sugar**: A reducing sugar is a sugar that can donate electrons to another chemical species, thus reducing it. This typically occurs when the sugar has a free aldehyde or ketone group.

2. **Identifying Reducing Sugars**: The key to identifying a reducing sugar is to look for a free hydroxyl (OH) group at the anomeric carbon (the first carbon in the sugar ring structure). If the anomeric carbon has a free OH group, the sugar is classified as a reducing sugar.

3. **Examples of Reducing Sugars**: Common examples of reducing sugars include glucose and fructose. Both of these sugars have a free OH group at their anomeric carbon.

4. **Identifying Non-Reducing Sugars**: A non-reducing sugar does not have a free OH group at the anomeric carbon. Instead, it may have a substituent such as a methoxy group (OCH3) at this position, which prevents it from acting as a reducing agent.

5. **Analyzing the Given Options**:
- Check each sugar structure provided in the options.
- Identify the anomeric carbon (C1) in each structure.
- Determine whether there is a free OH group at the anomeric carbon.

6. **Conclusion**: If one of the options has an anomeric carbon with a substituent like OCH3 instead of a free OH group, that sugar is a non-reducing sugar.

### Final Answer:
The non-reducing sugar among the given options is the one that has an OCH3 group at the anomeric carbon.

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