In which of the following pairs at least one of the compounds give positive Tollens test?

Options

A. a) Glucose and sucrose
B. b) Glucose and fructose
C. c) Fructose and sucrose
D. d) Maltose and sucrose

Explanation

To determine which pairs contain at least one compound that gives a positive Tollens' test, we need to identify the reducing sugars among the options provided. The Tollens' test is used to detect the presence of aldehydes and alpha-hydroxy ketones, which can reduce silver ions to metallic silver, forming a characteristic silver mirror.

### Step-by-Step Solution:

1. **Understand the Tollens' Test**:
- The Tollens' reagent is an ammoniacal silver nitrate solution. It is used to test for aldehydes and alpha-hydroxy ketones.
- Compounds that can give a positive Tollens' test are those that contain aldehyde groups or can be converted to aldehydes.

2. **Analyze Each Compound**:
- **Glucose**: Contains an aldehyde group (it is an aldose). Therefore, it can give a positive Tollens' test.
- **Fructose**: Contains a ketone group (it is a ketose). However, fructose can tautomerize to form an aldehyde under basic conditions, allowing it to give a positive Tollens' test.
- **Sucrose**: Is a disaccharide composed of glucose and fructose. It does not have a free aldehyde or ketone group and does not give a positive Tollens' test.
- **Maltose**: Is a disaccharide composed of two glucose units. It has a free aldehyde group and can give a positive Tollens' test.

3. **Evaluate the Given Options**:
- **Option A: Glucose and Sucrose**: Glucose gives a positive test; sucrose does not.
- **Option B: Glucose and Fructose**: Both glucose and fructose give a positive test.
- **Option C: Fructose and Sucrose**: Fructose gives a positive test; sucrose does not.
- **Option D: Maltose and Sucrose**: Maltose gives a positive test; sucrose does not.

4. **Conclusion**:
- The pairs that contain at least one compound that gives a positive Tollens' test are:
- Option A (Glucose)
- Option B (Glucose and Fructose)
- Option C (Fructose)
- Option D (Maltose)

### Final Answer:
All options contain at least one compound that gives a positive Tollens' test.

---