Ketone cannot by prepared by :

Options

A. Ozonolysis of alkenes
B. Heating of calcium salts of acids
C. Epoxidation of alkenes with peracids
D. Oxidation of a glycol with periodic acid

Answer

To determine which method cannot be used to prepare a ketone, let's analyze each option step by step:

### Step 1: Ozonolysis of Alkene
- **Explanation**: Ozonolysis involves the cleavage of alkenes using ozone (O₃) followed by hydrolysis. This reaction leads to the formation of carbonyl compounds, which can include ketones.
- **Conclusion**: Ozonolysis of alkenes can indeed produce ketones. **(This option is correct)**

### Step 2: Heating of Calcium Salt of Acid
- **Explanation**: When calcium salts of carboxylic acids are heated (dry distillation), they decompose to form ketones. The reaction involves the elimination of calcium carbonate (CaCO₃) and results in the formation of a ketone.
- **Conclusion**: Heating calcium salts of acids can produce ketones. **(This option is correct)**

### Step 3: Epoxidation of Alkene with Peracids
- **Explanation**: Epoxidation of alkenes using peracids (like m-chloroperbenzoic acid) forms an epoxide. When this epoxide undergoes hydrolysis, it results in the formation of diols (dihydroxy compounds) rather than ketones.
- **Conclusion**: Epoxidation of alkenes with peracids does not yield ketones. **(This option is incorrect)**

### Step 4: Epoxidation of Glycol with Periodic Acid
- **Explanation**: Glycols can be oxidized by periodic acid (HIO₄) to form aldehydes or ketones, depending on the structure of the glycol. If the glycol has a suitable structure, it can lead to the formation of ketones.
- **Conclusion**: Epoxidation of glycol with periodic acid can produce ketones. **(This option is correct)**

### Final Answer
Based on the analysis, the method that **cannot** be used to prepare a ketone is:
**Option 3: Epoxidation of Alkene with Peracids.**

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