Which compound gives yellow ppt.with iodine and alkali ?

Options

A. 2-hydroxy propane
B. Acetophenone
C. Methyl acetone
D. Acetamide

Answer

To determine which compound gives a yellow precipitate with iodine and alkali, we need to identify compounds that can undergo the iodoform test. The iodoform test is a qualitative test for the presence of a methyl ketone or a compound that can be oxidized to a methyl ketone.

### Step-by-Step Solution:

1. **Understand the Iodoform Test**:
The iodoform test is used to identify methyl ketones or compounds that can be converted into methyl ketones. The general reaction involves iodine (I2) and a base (usually NaOH or KOH) reacting with the compound to produce a yellow precipitate of iodoform (CHI3).

2. **Identify the Requirements**:
For a compound to give a positive iodoform test, it must meet two criteria:
- It must be a carbonyl compound (C=O).
- It must have a methyl group (CH3) adjacent to the carbonyl group (C=O).

3. **Evaluate the Given Compounds**:
We will analyze each compound to see if it meets the criteria for the iodoform test.

- **Acetophenone (C6H5C(O)CH3)**:
- Structure: Contains a carbonyl group (C=O) and a methyl group (CH3) adjacent to it.
- Conclusion: **Positive iodoform test** (gives yellow precipitate).

- **Methyl Acetate (CH3C(O)OCH3)**:
- Structure: Contains a carbonyl group (C=O) but does not have a methyl group adjacent to it in the required form (it is an ester).
- Conclusion: **Negative iodoform test** (does not give yellow precipitate).

- **Acetamide (CH3C(O)NH2)**:
- Structure: Contains a carbonyl group (C=O) but is an amide, not a ketone, and does not have the required methyl group structure.
- Conclusion: **Negative iodoform test** (does not give yellow precipitate).

- **2-Hydroxypropane (CH3CHOHCH3)**:
- Structure: This compound can be oxidized to acetone (C3H6O), which has a carbonyl group (C=O) and a methyl group (CH3) adjacent to it.
- Conclusion: **Positive iodoform test** (gives yellow precipitate).

4. **Final Conclusion**:
The compounds that give a yellow precipitate with iodine and alkali in the iodoform test are **Acetophenone** and **2-Hydroxypropane**.