Nucleophilic addition reaction will be most favoured in

Options

A. `CH_(3)-CH_(2)-CH_(2)overset(O)overset(||)(C)-CH_(3)`
B. `(CH_(3))_(2)C=O`
C. `CH_(2)CH_(2)CHO`
D. `CH_(3)CHO`

Answer

To determine which compound will favor nucleophilic addition reactions the most, we need to analyze the electrophilicity of the carbonyl carbon in each option provided. The more positive charge density on the carbonyl carbon, the more favorable the nucleophilic attack will be.

### Step-by-Step Solution:

1. **Understanding Nucleophilic Addition**:
- Nucleophilic addition reactions involve a nucleophile (a species with a negative charge or electron-rich) attacking an electrophile (a species with a positive charge or electron-deficient).
- The electrophilic center in this case is the carbonyl carbon (C=O) in aldehydes and ketones.

2. **Evaluating Electrophilicity**:
- The strength of the nucleophilic attack depends on the electrophilicity of the carbonyl carbon. The more positive the carbon is (higher positive charge density), the more favorable the nucleophilic attack will be.

3. **Analyzing Each Option**:
- **Option A**: R1 = CH3, R2 = CH3, R3 = CH2, R4 = CO (This is a ketone)
- The carbonyl carbon here is surrounded by two methyl groups, which have a +I (inductive) effect, reducing the positive charge on the carbonyl carbon.

- **Option B**: R1 = CH3, R2 = CH3, R3 = CO (This is also a ketone)
- Similar to option A, but with one less carbon. The +I effect is still present but slightly less than in option A.

- **Option C**: R1 = CH3, R2 = CH2, R3 = CHO (This is an aldehyde)
- The carbonyl carbon is less hindered and has one less +I effect compared to the ketones in options A and B, making it more electrophilic than the previous options.

- **Option D**: R1 = CH3, R2 = CHO (This is also an aldehyde)
- This carbonyl carbon has the least +I effect due to having only one carbon attached, making it the most electrophilic among the options.

4. **Conclusion**:
- After analyzing the electrophilicity of each carbonyl carbon, we find that **Option D** (with the least +I effect) will favor nucleophilic addition reactions the most.

### Final Answer:
**Option D** will favor nucleophilic addition reactions the most.