A chromatography column, packed with silica gel as stationary phase, was used to separate a mixture of compounds consisting of (A) benzanilide (B) aniline and (C) acetophenone. When the column is eluted with a mixture of solvents, hexane : ethyl acetate (20 : 80), the sequence of obtained compounds is

Options

A. (B), (C) and (A)
B. (B), (A) and (C)
C. (A), (B) and (C)
D. (C), (A) and (B)

Answer

To solve the problem of separating a mixture of compounds (A) benzanilide, (B) aniline, and (C) acetophenone using a chromatography column packed with silica gel and eluted with a mixture of solvents (hexane: ethyl acetate in a 20:80 ratio), we can follow these steps:

### Step 1: Understand the Compounds
- **Benzanilide (A)**: This compound has both a benzene ring and an amide functional group, making it relatively polar.
- **Aniline (B)**: Aniline contains an amino group (-NH2) attached to a benzene ring, which also makes it polar.
- **Acetophenone (C)**: This compound has a ketone functional group (C=O) attached to a benzene ring, making it polar as well.

### Step 2: Identify the Polarity of the Solvents
- **Hexane**: A non-polar solvent.
- **Ethyl Acetate**: A polar solvent.

### Step 3: Analyze the Mixture and Solvent Composition
The solvent mixture is 20% hexane (non-polar) and 80% ethyl acetate (polar). Since the polar solvent is in greater quantity, it will preferentially interact with the more polar compounds in the mixture.

### Step 4: Determine the Order of Elution
In column chromatography, the order of elution is determined by the polarity of the compounds:
- The more polar compounds will interact more with the polar solvent (ethyl acetate) and will elute first.
- The less polar compounds will interact more with the stationary phase (silica gel) and will elute later.

### Step 5: Rank the Compounds by Polarity
1. **Acetophenone (C)**: Most polar due to the presence of the ketone group.
2. **Aniline (B)**: Polar due to the amino group.
3. **Benzanilide (A)**: Least polar compared to the others due to the presence of the amide group but still polar.

### Step 6: Write the Sequence of Elution
Based on the above analysis, the sequence of elution from the chromatography column will be:
1. **Acetophenone (C)** - elutes first
2. **Aniline (B)** - elutes second
3. **Benzanilide (A)** - elutes last

### Final Answer
The sequence of obtained compounds is: **C (Acetophenone), B (Aniline), A (Benzanilide)**.

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