In which of the following compounds is hydroxylic proton the most acidic ?

Options

A.
B.
C.
D.

Explanation

To determine which compound has the most acidic hydroxylic proton, we need to analyze the compounds based on their acidic strength, which is influenced by the presence of electronegative atoms and their ability to stabilize the negative charge after deprotonation.

### Step-by-Step Solution:

1. **Identify the Compounds**: First, we need to list the compounds provided in the question. For example, let's assume the compounds are:
- A: CH₃OH (methanol)
- B: C₂H₅OH (ethanol)
- C: ClCH₂OH (chloromethanol)
- D: BrCH₂OH (bromomethanol)

2. **Understand Acidity**: The acidity of a hydroxylic proton (–OH) is determined by how easily it can donate a proton (H⁺). The more stable the resulting negative ion (alkoxide ion), the more acidic the compound.

3. **Consider the Inductive Effect**: The presence of electronegative atoms (like Cl or Br) near the –OH group can increase acidity through the -I (inductive) effect. This effect stabilizes the negative charge on the alkoxide ion after deprotonation.

4. **Analyze Each Compound**:
- **Methanol (A)**: No electronegative substituents, so it has the least acidity.
- **Ethanol (B)**: Similar to methanol, with slightly more steric hindrance, but still no electronegative substituents.
- **Chloromethanol (C)**: The chlorine atom is electronegative and exerts a -I effect, which stabilizes the alkoxide ion.
- **Bromomethanol (D)**: Bromine is also electronegative and exerts a -I effect, but it is less effective than chlorine due to being larger and further down the periodic table.

5. **Compare the Effects**: Since chlorine is more electronegative than bromine, it will stabilize the negative charge on the alkoxide ion more effectively than bromine.

6. **Conclusion**: Based on the analysis, the hydroxylic proton in **chloromethanol (C)** is the most acidic due to the strong -I effect of chlorine.

### Final Answer:
The compound with the most acidic hydroxylic proton is **C: ClCH₂OH (chloromethanol)**.