Arrange the following compound in increasing order of reactivity towards nucleophilic addition reaction
(I) `C_(6)H_(5)COCH_(3)` (II) `CH_(3)CO - C_(2)H_(5)`
`C_(6)H_(5)CHO` (IV) `CI - CH_(2) - CHO`

Options

A. IV `gt` III `gt` II `gt` I
B. IV `gt` II `gt` III `gt` I
C. I `gt` II `gt` III `gt` IV
D. III `gt` IV `gt` II `gt` I

Explanation

To determine the increasing order of reactivity towards nucleophilic addition reactions for the given compounds, we need to analyze the structure of each compound and identify the electrophilic carbon atom (the carbon in the carbonyl group, C=O) and the factors that influence its reactivity.

### Given Compounds:
1. (I) `C6H5COCH3` (Acetophenone)
2. (II) `CH3COC2H5` (Butan-2-one)
3. (III) `C6H5CHO` (Benzaldehyde)
4. (IV) `Cl-CH2-CHO` (Chloroacetaldehyde)

### Step 1: Identify the Electrophilic Centers
The electrophilic center in these compounds is the carbon atom in the carbonyl group (C=O). The reactivity towards nucleophilic addition depends on the electron density around this carbon atom.

### Step 2: Analyze Each Compound
1. **Acetophenone (I)**: The carbonyl carbon is bonded to a phenyl group (C6H5) and a methyl group (CH3). The phenyl group has a resonance effect (−R effect) that decreases the positive character of the carbonyl carbon, making it less reactive.

2. **Butan-2-one (II)**: The carbonyl carbon is bonded to two alkyl groups (methyl and ethyl). Alkyl groups have a +I (inductive) effect which increases the electron density on the carbonyl carbon, making it more reactive than acetophenone.

3. **Benzaldehyde (III)**: The carbonyl carbon is bonded to a phenyl group and a hydrogen atom. The phenyl group has a −R effect, similar to acetophenone, but since it is directly attached to the carbonyl carbon, it makes benzaldehyde more reactive than acetophenone due to the absence of steric hindrance from an alkyl group.

4. **Chloroacetaldehyde (IV)**: The carbonyl carbon is bonded to a chlorine atom and a hydrogen atom. Chlorine is an electron-withdrawing group (−I effect), which increases the positive character of the carbonyl carbon, making it the most reactive towards nucleophilic addition.

### Step 3: Arrange the Compounds in Increasing Order of Reactivity
Based on the analysis:
- (I) Acetophenone is the least reactive due to the −R effect of the phenyl group.
- (II) Butan-2-one is more reactive than acetophenone due to the +I effect of the alkyl groups.
- (III) Benzaldehyde is more reactive than both acetophenone and butan-2-one due to the direct attachment of the phenyl group.
- (IV) Chloroacetaldehyde is the most reactive due to the strong −I effect of chlorine.

### Final Order of Reactivity
The increasing order of reactivity towards nucleophilic addition reaction is:
**(I) < (II) < (III) < (IV)**