Which of the following give positive iodoform test ?
(1) Ethanol, (2) Ethanal
(3) Butan-1-ol, (4) Butan-2-ol
(5) Phenyl ethanol.

Options

A. 1, 2 and 5
B. 1, 3 and 4
C. 1, 2 and 3
D. 1, 2 and 4

Explanation

To determine which of the given compounds give a positive iodoform test, we need to analyze each compound based on the criteria for the iodoform test. The iodoform test is positive for compounds that contain a methyl ketone group (C=O with a methyl group, CH3) or for certain alcohols that can be oxidized to such ketones.

### Step-by-Step Solution:

1. **Ethanol (C2H5OH)**:
- Ethanol is a primary alcohol. When oxidized, it forms acetaldehyde (ethanal), which has the structure CH3CHO.
- Acetaldehyde contains a methyl group adjacent to the carbonyl group (C=O), thus it can give a positive iodoform test.
- **Conclusion**: Ethanol gives a positive iodoform test.

2. **Ethanal (CH3CHO)**:
- Ethanal is an aldehyde that contains a methyl group adjacent to the carbonyl group.
- Therefore, it also gives a positive iodoform test.
- **Conclusion**: Ethanal gives a positive iodoform test.

3. **Butan-1-ol (C4H10O)**:
- Butan-1-ol is a primary alcohol. When oxidized, it forms butanal (C4H8O), which does not have a methyl group adjacent to the carbonyl.
- Therefore, it does not give a positive iodoform test.
- **Conclusion**: Butan-1-ol does not give a positive iodoform test.

4. **Butan-2-ol (C4H10O)**:
- Butan-2-ol is a secondary alcohol. When oxidized, it forms butanone (C4H8O), which has the structure CH3C(=O)CH2CH3.
- This structure contains a methyl group adjacent to the carbonyl group, thus it gives a positive iodoform test.
- **Conclusion**: Butan-2-ol gives a positive iodoform test.

5. **Phenyl ethanol (C6H5CH2OH)**:
- Phenyl ethanol is a primary alcohol. When oxidized, it forms phenyl acetaldehyde (C6H5CHO), which does not have a methyl group adjacent to the carbonyl.
- Therefore, it does not give a positive iodoform test.
- **Conclusion**: Phenyl ethanol does not give a positive iodoform test.

### Summary of Results:
- Ethanol: Positive iodoform test
- Ethanal: Positive iodoform test
- Butan-1-ol: Negative iodoform test
- Butan-2-ol: Positive iodoform test
- Phenyl ethanol: Negative iodoform test

### Final Answer:
The compounds that give a positive iodoform test are Ethanol (1), Ethanal (2), and Butan-2-ol (4).

### Correct Option:
The correct answer is D (1, 2, and 4).

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