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 the compounds propanal, butanone, propanone, and benzaldehyde, we need to analyze the structure and reactivity of each compound. Here’s a step-by-step breakdown:

### Step 1: Identify the Compounds
1. **Propanal (CH3CH2CHO)**: This is an aldehyde.
2. **Butanone (CH3CH2COCH3)**: This is a ketone.
3. **Propanone (CH3COCH3)**: This is also a ketone.
4. **Benzaldehyde (C6H5CHO)**: This is an aldehyde.

### Step 2: Understand Nucleophilic Addition
Nucleophilic addition reactions occur at the carbonyl carbon of aldehydes and ketones. The reactivity of these compounds in nucleophilic addition is influenced by:
- The type of carbonyl compound (aldehyde vs. ketone).
- Steric hindrance around the carbonyl carbon.
- Electron-withdrawing or donating effects of substituents.

### Step 3: Compare Aldehydes and Ketones
- **Aldehydes** (like propanal and benzaldehyde) are generally more reactive than ketones because they have only one alkyl group (which is less sterically hindered) compared to ketones, which have two alkyl groups.
- Between the two aldehydes, propanal has an ethyl group (more electron-donating) compared to benzaldehyde, which has a phenyl group (less electron-donating). Therefore, propanal is more reactive than benzaldehyde.

### Step 4: Compare the Ketones
- For the ketones, butanone and propanone, we need to consider the substituents:
- **Butanone** has an ethyl group and a methyl group.
- **Propanone** has two methyl groups.
- The ethyl group in butanone is more electron-donating than the methyl groups in propanone, making butanone slightly more reactive than propanone.

### Step 5: Arrange in Decreasing Order of Reactivity
Based on the above analysis, we can arrange the compounds in decreasing order of nucleophilic addition reactivity:
1. **Propanal** (most reactive due to being an aldehyde with a strong electron-donating group).
2. **Benzaldehyde** (less reactive than propanal but more reactive than ketones).
3. **Butanone** (more reactive than propanone due to the presence of an ethyl group).
4. **Propanone** (least reactive due to having two methyl groups).

### Final Order
Thus, the final decreasing order of nucleophilic addition reactions for the compounds is:
**Propanal > Benzaldehyde > Butanone > Propanone**