Which of the following cannot show tautomerism ?

Options

A. methanal
B. benzaldehyde
C. benzophenone
D. Acetone

Explanation

To determine which of the given compounds cannot show tautomerism, we need to analyze each compound based on the presence of alpha hydrogen atoms. Tautomerism typically occurs between a keto form and an enol form, and the presence of alpha hydrogen is essential for this process.

### Step-by-Step Solution:

1. **Understanding Tautomerism**:
- Tautomerism is a chemical reaction that involves the rearrangement of bonds within a compound, typically between a keto form (C=O) and an enol form (C=C-OH).
- The key requirement for tautomerism is the presence of alpha hydrogen atoms adjacent to the carbonyl carbon.

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