Arrange the following in order of increasing reactivity towards nucleophilic substitution reaction
`underset((1))(CH_3-overset(O)overset(||)(C)-CH_(2)CH_3)" "underset((2))(CH_3-overset(O)overset(||)(C)-Cl)" "underset((3))(CH_3-overset(O)overset(||)(C)-NH-CH_3)`

Options

A. `1 lt 2 lt 3`
B. `3 lt 1 lt 2`
C. `1 lt 3 lt 2`
D. `2 lt 1 lt 3`

Answer

To determine the order of increasing reactivity towards nucleophilic substitution reactions for the given compounds, we need to analyze the electrophilic centers in each compound and the effects of substituents on the carbonyl carbon.

### Step-by-Step Solution:

1. **Identify the Compounds**:
- Compound 1: \( CH_3-C(=O)-CH_2CH_3 \) (Butyryl group)
- Compound 2: \( CH_3-C(=O)-Cl \) (Acyl chloride)
- Compound 3: \( CH_3-C(=O)-NH-CH_3 \) (Acetamide)

2. **Determine the Electrophilic Center**:
- In each compound, the carbonyl carbon (C=O) is the electrophilic center because it is electron-deficient due to the electronegativity of oxygen.

3. **Analyze the Effects of Substituents**:
- **Compound 1**: The carbonyl carbon is bonded to a methyl group and an ethyl group. Both groups have a +I (inductive) effect, which increases the electron density on the carbonyl carbon, making it less reactive towards nucleophiles.
- **Compound 2**: The carbonyl carbon is bonded to a chlorine atom, which has a -I effect. This decreases the electron density on the carbonyl carbon, making it more reactive towards nucleophiles compared to Compound 1.
- **Compound 3**: The carbonyl carbon is bonded to a nitrogen atom (NH-CH3), which has a +I effect. However, the nitrogen also has lone pairs that can stabilize the carbonyl carbon, making it less reactive than Compound 2 but more reactive than Compound 1.

4. **Order of Reactivity**:
- Based on the analysis:
- Compound 1 (least reactive) < Compound 3 < Compound 2 (most reactive)
- Therefore, the order of increasing reactivity towards nucleophilic substitution is:
\[ \text{Compound 1} < \text{Compound 3} < \text{Compound 2} \]

### Final Answer:
The order of increasing reactivity towards nucleophilic substitution reaction is:
\[ \text{(1) } CH_3-C(=O)-CH_2CH_3 < \text{(3) } CH_3-C(=O)-NH-CH_3 < \text{(2) } CH_3-C(=O)-Cl \]