Which of the following named reaction is not used for introducing a - COOH group ?

Options

A. Cannizzaro reaction
B. Benzylic acid rearrangement
C. lodoform reaction
D. none of these

Answer

To solve the question of which named reaction is not used for introducing a -COOH (carboxylic acid) group, we will analyze each of the reactions mentioned in the options.

### Step-by-Step Solution:

1. **Identify the Reactions**: The question refers to several named reactions. We need to evaluate each one to see if it introduces a -COOH group.

2. **Canizzaro Reaction**:
- The Canizzaro reaction involves aldehydes that do not have an alpha hydrogen.
- In this reaction, one molecule of the aldehyde is oxidized to a carboxylic acid (-COOH), while another is reduced to an alcohol (-CH2OH).
- Therefore, the Canizzaro reaction does introduce a -COOH group.

3. **Iodoform Reaction**:
- The Iodoform reaction occurs with methyl ketones or aldehydes, where the presence of a methyl group adjacent to a carbonyl group leads to the formation of iodoform (CHI3) and a carboxylate ion (RCOO-).
- The carboxylate ion can be converted to a carboxylic acid (-COOH) upon acidification.
- Thus, the Iodoform reaction also introduces a -COOH group.

4. **Benzylic Rearrangement**:
- In the benzylic rearrangement, a base attacks a diketone structure, leading to the formation of a carboxylic acid.
- The rearrangement results in the formation of a -COOH group.
- Therefore, the benzylic rearrangement introduces a -COOH group as well.

5. **Conclusion**:
- After analyzing the three reactions, we find that all of them (Canizzaro reaction, Iodoform reaction, and Benzylic rearrangement) are capable of introducing a -COOH group.
- If the options included a fourth reaction that does not introduce a -COOH group, that would be the correct answer. However, based on the analysis, if all listed reactions introduce a -COOH group, we conclude that the answer is that none of the listed reactions fail to introduce a -COOH group.

### Final Answer:
None of the listed reactions fail to introduce a -COOH group.

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