Which of the following has maximum `pK_(a)` value?

Options

A.
B.
C.
D.

Explanation

To determine which of the given alcohols has the maximum pK_a value, we need to understand the relationship between pK_a and acidity. The pK_a value is inversely related to the acidity of a compound; the higher the pK_a value, the weaker the acid, and vice versa.

### Step-by-Step Solution:

1. **Identify the Types of Alcohols**:
- The question mentions four alcohols, including primary alcohols, secondary alcohols, and tertiary alcohols.
- For example, let’s assume we have the following types:
- 1° Alcohol (e.g., Ethanol)
- 2° Alcohol (e.g., Isopropanol)
- 3° Alcohol (e.g., Tert-butanol)

2. **Understand Acidity of Alcohols**:
- Alcohols can be classified based on their structure:
- Primary alcohols (1°) are generally more acidic than secondary (2°) alcohols.
- Secondary alcohols (2°) are more acidic than tertiary (3°) alcohols.
- This is due to the inductive effect of alkyl groups. Alkyl groups are electron-donating and stabilize the negative charge on the alkoxide ion (RO⁻) formed after deprotonation. The more alkyl groups attached, the less acidic the alcohol becomes.

3. **Determine the pK_a Values**:
- Tertiary alcohols (3°) have the least acidic character due to the presence of three alkyl groups, which provide a strong +I effect, destabilizing the alkoxide ion.
- Therefore, tertiary alcohols have the highest pK_a values compared to primary and secondary alcohols.

4. **Conclusion**:
- Since tertiary alcohols are the least acidic, they have the maximum pK_a value among the given options.
- Therefore, the correct answer is the tertiary alcohol.

### Final Answer:
The alcohol with the maximum pK_a value is the tertiary alcohol.