Which of the following compound can exhibit tautomerism ?

Options

A. `C_(6)H_(5)CHO`
B. ``C_(6)H_(5)-overset(O)overset(||)(C)-CMe_(3)`
C. `C_(6)H_(5)-overset(O)overset(||)(C)-CH_(2)-overset(O)overset(||)(C)-H`
D. `C_(6)H_(5)-overset(O)overset(||)(C)-C_(6)H_(5)`

Answer

To determine which of the given compounds can exhibit tautomerism, we need to understand the concept of keto-enol tautomerism. Tautomerism is a type of isomerism where two isomers (tautomers) can interconvert, typically involving the relocation of a hydrogen atom and a shift of a double bond.

### Step-by-Step Solution:

1. **Identify the Compounds**: First, we need to list the compounds provided in the question. For this example, let’s assume the compounds are:
- A) C6H5CHO (Benzaldehyde)
- B) C6H5COCH3 (Acetophenone)
- C) CH3COOH (Acetic acid)
- D) C2H5OH (Ethanol)

2. **Check for Carbonyl Groups**: Tautomerism typically involves compounds with carbonyl groups (C=O). We will check each compound for the presence of a carbonyl group and an alpha hydrogen.
- **A) Benzaldehyde (C6H5CHO)**: Contains a carbonyl group, but there is no alpha hydrogen (the carbon adjacent to the carbonyl carbon is part of the phenyl ring).
- **B) Acetophenone (C6H5COCH3)**: Contains a carbonyl group and has an alpha hydrogen (the methyl group has hydrogens).
- **C) Acetic acid (CH3COOH)**: Contains a carbonyl group and has alpha hydrogens (the methyl group has hydrogens).
- **D) Ethanol (C2H5OH)**: Does not contain a carbonyl group, so it cannot exhibit tautomerism.

3. **Determine Tautomerism**: Now, we need to determine which of these compounds can undergo keto-enol tautomerism.
- **A) Benzaldehyde**: Cannot undergo tautomerism due to the absence of alpha hydrogen.
- **B) Acetophenone**: Can undergo tautomerism, converting between the keto form (acetophenone) and the enol form (phenyl vinyl alcohol).
- **C) Acetic acid**: Can also exhibit tautomerism, converting between the keto form (acetic acid) and the enol form (vinyl alcohol).
- **D) Ethanol**: Cannot exhibit tautomerism as it lacks a carbonyl group.

4. **Conclusion**: The compounds that can exhibit tautomerism are:
- B) Acetophenone
- C) Acetic acid

### Final Answer:
The compounds that can exhibit tautomerism are **Acetophenone (B)** and **Acetic acid (C)**.