Acetaldehyde cannot exhibit

Options

A. lodoform test
B. Lucas test
C. Benedict's test
D. Tollen's test

Answer

To determine which test acetaldehyde cannot exhibit, we need to analyze the properties of acetaldehyde (CH₃CHO) and the tests it undergoes.

### Step-by-Step Solution:

1. **Identify Acetaldehyde**:
Acetaldehyde is a simple aldehyde with the molecular formula CH₃CHO. It has a carbonyl group (C=O) and is known for its reactivity in various chemical tests.

2. **Understand the Tests**:
- **Lucas Test**: This test is used to differentiate between primary, secondary, and tertiary alcohols. It involves the reaction of alcohols with Lucas reagent (ZnCl₂ in HCl) to form alkyl chlorides. Aldehydes do not react in this test.
- **Tollens' Test**: This test can be performed on aldehydes, where they are oxidized to carboxylic acids while reducing Ag⁺ to metallic silver.
- **Fehling's Test**: Similar to Tollens', this test is also applicable to aldehydes, where they reduce the copper(II) ions to copper(I) oxide.
- **Benedict's Test**: Like Fehling's test, this is another test for reducing sugars and aldehydes.

3. **Analyze Acetaldehyde's Reactivity**:
Acetaldehyde can undergo Tollens', Fehling's, and Benedict's tests due to its aldehyde functional group. However, it does not react in the Lucas test because it is not an alcohol.

4. **Conclusion**:
Based on the above analysis, the test that acetaldehyde cannot exhibit is the **Lucas test**.

### Final Answer:
Acetaldehyde cannot exhibit the Lucas test.