Write down decreasing order of nucleophilic addition reaction of following
Propanal, Butanone, Propanone, Benzaldehyde

Options

A. `Propanal gt Butanone gt Propanone gt Benzaldehyde`
B. `Propanal gt Benzaldehyde gt Propanone gt Butanone`
C. `Propanone gt Propanal gt Butanone gt Benzaldehyde`
D. `Propanone gt Butanone gt Benzaldehyde gt Propanal`

Answer

To determine the decreasing order of nucleophilic addition reactions for Propanal, Butanone, Propanone, and Benzaldehyde, we need to analyze the structures and the electron-donating or withdrawing effects of the substituents on the carbonyl carbon.

### Step-by-Step Solution:

1. **Identify the Structures**:
- **Propanal (CH3CH2CHO)**: An aldehyde with one alkyl group (ethyl) and a hydrogen attached to the carbonyl carbon.
- **Butanone (CH3COCH2CH3)**: A ketone with two alkyl groups (methyl and ethyl) attached to the carbonyl carbon.
- **Propanone (CH3COCH3)**: A ketone with two methyl groups attached to the carbonyl carbon.
- **Benzaldehyde (C6H5CHO)**: An aldehyde with a phenyl group attached to the carbonyl carbon.

2. **Analyze the Electron Effects**:
- **Propanal**: The ethyl group is an electron-donating group, which increases electron density on the carbonyl carbon, making it less electrophilic and thus less reactive.
- **Butanone**: The presence of both a methyl and an ethyl group also donates electron density, but the effect is more pronounced than in propanal due to having two groups.
- **Propanone**: With two methyl groups, the electron donation is significant, reducing the electrophilicity of the carbonyl carbon even more than butanone.
- **Benzaldehyde**: The phenyl group is electron-rich and withdraws electron density from the carbonyl carbon due to resonance, making it less reactive than the others.

3. **Determine the Reactivity Order**:
- The more electron-donating groups present, the less reactive the carbonyl compound will be towards nucleophilic addition.
- Therefore, the order of reactivity from most to least reactive is:
- **Propanal** (most reactive due to one electron-donating group)
- **Butanone** (less reactive due to two electron-donating groups)
- **Propanone** (even less reactive due to two methyl groups)
- **Benzaldehyde** (least reactive due to resonance stabilization from the phenyl group)

4. **Final Order**:
- The decreasing order of nucleophilic addition reactions is:
- Propanal > Butanone > Propanone > Benzaldehyde

### Final Answer:
**Decreasing Order of Nucleophilic Addition Reaction**: Propanal > Butanone > Propanone > Benzaldehyde