Which of the following does not exhibit tautomerism?

Options

A.
B.
C.
D.

Explanation

To determine which compound does not exhibit tautomerism, we need to analyze the compounds based on the conditions for tautomerism.

### Step-by-Step Solution:

1. **Understanding Tautomerism**:
Tautomerism is a type of isomerism where two or more isomers (tautomers) can interconvert, typically involving the relocation of a hydrogen atom and a shift of a double bond. The common example is keto-enol tautomerism.

2. **Conditions for Tautomerism**:
- There must be a carbonyl group (C=O) present.
- The carbon atom in the carbonyl group must be attached to a more electronegative atom (like oxygen).
- There should be at least one alpha-hydrogen atom on an sp³ hybridized carbon adjacent to the carbonyl carbon.

3. **Analyzing Each Compound**:
- **Compound 1**: Check for sp² hybridization and presence of alpha-hydrogens. If the carbonyl carbon is sp² hybridized and lacks alpha-hydrogens, it cannot exhibit tautomerism.
- **Compound 2**: Check if it has sp³ hybridized carbons and alpha-hydrogens. If both conditions are satisfied, it can exhibit tautomerism.
- **Compound 3**: Similar to Compound 2, check for sp³ hybridization and alpha-hydrogens.
- **Compound 4**: Again, check for sp³ hybridization and alpha-hydrogens.

4. **Conclusion**:
After analyzing all compounds:
- Compound 1 is sp² hybridized and does not have the required alpha-hydrogens, therefore it does not exhibit tautomerism.
- Compounds 2, 3, and 4 have sp³ hybridized carbons with alpha-hydrogens, allowing them to exhibit tautomerism.

### Final Answer:
The compound that does not exhibit tautomerism is **Compound 1**.

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