Which of the following is reducing and non-reactive sugar ?

Options

A. Galactose
B. Gluconic acid
C. Methygalactoside
D. Sucrose

Answer

To determine which of the following options is a reducing and non-reactive sugar, we need to analyze each option based on their chemical structure and properties.

**Step 1: Understand the definitions**
- **Reducing sugars** are those that have a free aldehyde or ketone group, allowing them to be easily oxidized by mild oxidizing agents.
- **Non-reactive sugars** are those that do not participate in certain reactions, such as the Benedict's test, which is used to identify reducing sugars.

**Step 2: Analyze the options**
1. **Galactose**:
- It is a monosaccharide (C6H12O6) and has a free aldehyde group. Therefore, it is a reducing sugar. However, it shows no response in the Benedict's test, making it non-reactive in this context.

2. **Gluconic acid**:
- This is a derivative of glucose and contains a carboxylic acid group. It is also a reducing sugar but reacts in the Benedict's test.

3. **Methyl galactoside**:
- This is a glycoside and does not have a free aldehyde or ketone group, making it a non-reducing sugar. However, it is not classified as non-reactive in the context of the question.

4. **Sucrose**:
- This is a disaccharide composed of glucose and fructose. It does not have a free aldehyde or ketone group, making it a non-reducing sugar. It reacts positively in the Benedict's test.

**Step 3: Conclusion**
- Among the options provided, **Galactose** is the only sugar that is both reducing (due to its free aldehyde group) and non-reactive (as it does not show a response in the Benedict's test).

**Final Answer**: Galactose

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