Arrange the following compounds in increasing order of their reactivity in nucleophilic addition reactions.
Ethanal, Propanal, Propanone, Butanone

Options

A. Butanone lt Propanone lt Propanal lt Ethanal
B. Propanone lt Butanone lt Ethanal gt Propanal
C. Propanal lt Ethanal lt Propanone lt Butanone
D. Ethanal lt Propanal lt Propanone lt Butanone

Explanation

To arrange the compounds Ethanal, Propanal, Propanone, and Butanone in increasing order of their reactivity in nucleophilic addition reactions, we need to analyze the structure of each compound and the effect of substituents on the carbonyl carbon's electrophilicity.

### Step-by-Step Solution:

1. **Identify the Compounds**:
- Ethanal (CH3CHO)
- Propanal (CH3CH2CHO)
- Propanone (CH3COCH3)
- Butanone (CH3CH2COCH3)

2. **Understand Nucleophilic Addition**:
- Nucleophilic addition reactions involve the attack of a nucleophile on the electrophilic carbon of the carbonyl group (C=O). The reactivity of carbonyl compounds in these reactions depends on the electron-withdrawing or electron-donating effects of the substituents attached to the carbonyl carbon.

3. **Analyze the Electron-Donating and Electron-Withdrawing Effects**:
- **Electrophilicity**: The more positive charge on the carbonyl carbon, the more reactive it is towards nucleophiles.
- **Inductive Effect**: Alkyl groups (like CH3 and CH2) are electron-donating (they have a +I effect), which decreases the positive charge on the carbonyl carbon, making it less reactive.
- **Steric Hindrance**: Larger groups can also hinder the approach of nucleophiles.

4. **Reactivity Order**:
- **Ethanal (CH3CHO)**: Has one alkyl group (methyl), making it moderately reactive.
- **Propanal (CH3CH2CHO)**: Has two alkyl groups (ethyl and methyl), making it less reactive than ethanal.
- **Propanone (CH3COCH3)**: Has two methyl groups, which provide significant +I effect, making it less reactive than both ethanal and propanal.
- **Butanone (CH3CH2COCH3)**: Similar to propanone, but with an additional ethyl group, making it the least reactive due to increased +I effect.

5. **Final Order**:
- Based on the analysis, the increasing order of reactivity in nucleophilic addition reactions is:
- Butanone < Propanone < Propanal < Ethanal

### Summary of the Increasing Order of Reactivity:
- **Butanone < Propanone < Propanal < Ethanal**