Which among the following compounds will show keto-enol tautomerism

Options

A. 2,2- dimethylpropanal
B. 2,2- dimethyl -1- nitropropane
C. Acetyl acetone
D. Benzophenone

Answer

To determine which of the given compounds shows keto-enol tautomerism, we need to analyze each compound for the presence of a keto group and an alpha hydrogen. Let's go through the compounds step by step:

### Step 1: Understanding Keto-Enol Tautomerism
Keto-enol tautomerism is a chemical equilibrium between a keto form (with a carbonyl group, C=O) and an enol form (with a hydroxyl group, -OH, and a double bond, C=C). For a compound to exhibit this tautomerism, it must have:
- A keto group (C=O)
- An alpha hydrogen (a hydrogen atom attached to the carbon adjacent to the carbonyl carbon)

### Step 2: Analyzing Each Compound
1. **2,2-Dimethylpropanol**:
- Structure: (CH3)2C(OH)CH3
- This compound has a hydroxyl group but does not contain a keto group (C=O).
- **Conclusion**: Does not show keto-enol tautomerism.

2. **2,2-Dimethyl-1-nitropropanol**:
- Structure: (CH3)2C(NO2)CH2OH
- Similar to the first compound, it does not have a keto group.
- **Conclusion**: Does not show keto-enol tautomerism.

3. **Acetylacetone**:
- Structure: CH3C(=O)CH2C(=O)CH3
- This compound has a keto group (C=O) and an alpha hydrogen (the hydrogen on the methylene group adjacent to the keto group).
- **Conclusion**: Shows keto-enol tautomerism.

4. **Benzophenone**:
- Structure: C6H5C(=O)C6H5
- This compound has a keto group (C=O) but lacks an alpha hydrogen (there are no hydrogens on the carbon adjacent to the carbonyl).
- **Conclusion**: Does not show keto-enol tautomerism.

### Step 3: Final Conclusion
Among the compounds analyzed, only **acetylacetone** exhibits keto-enol tautomerism due to the presence of both a keto group and an alpha hydrogen.

### Answer:
**Acetylacetone** is the compound that shows keto-enol tautomerism.

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