Ketones are generally less reactive than Aldehydes in nucleophilic addition reactions because

Options

A. Carbonyl carbon in ketones is sterically more protected and more electrophilic
B. Carbonyl carbon in aldehydes is sterically more protected and more electrophilic
C. Carbonyl carbon in aldehydes is sterically less protected and less electrophilic
D. Carbonyl carbon in ketones is sterically more protected and less electrophilic

Answer

**Step-by-Step Solution:**

1. **Understanding the Structure of Aldehydes and Ketones:**
- Aldehydes have the general structure RCHO, where R is a hydrogen atom or an alkyl group. The carbonyl carbon is bonded to a hydrogen atom and an alkyl group.
- Ketones have the general structure RC(=O)R', where R and R' are alkyl groups. The carbonyl carbon is bonded to two alkyl groups.

2. **Electrophilicity of Carbonyl Carbon:**
- In both aldehydes and ketones, the carbonyl carbon is electrophilic due to the partial positive charge created by the electronegativity of the oxygen atom.
- However, the presence of two alkyl groups in ketones increases the electron density around the carbonyl carbon through the +I (inductive) effect of the alkyl groups.

3. **Effect of Alkyl Groups:**
- In ketones, the two alkyl groups exert a +I effect, which stabilizes the positive charge on the carbonyl carbon. This stabilization reduces the electrophilicity of the carbonyl carbon, making it less reactive towards nucleophiles.
- In contrast, aldehydes have only one alkyl group and one hydrogen atom. The hydrogen does not contribute to the +I effect, making the carbonyl carbon in aldehydes more electrophilic and thus more reactive.

4. **Conclusion:**
- Therefore, ketones are generally less reactive than aldehydes in nucleophilic addition reactions due to the presence of two alkyl groups that stabilize the positive charge on the carbonyl carbon, reducing its electrophilicity.

**Final Answer:**
Ketones are less reactive than aldehydes in nucleophilic addition reactions because the two alkyl groups in ketones stabilize the positive charge on the carbonyl carbon through the +I effect, making it less electrophilic compared to the carbonyl carbon in aldehydes, which has only one alkyl group and a hydrogen atom.

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