Which one of the following phenols has the highestpK value?

Options

A. o-Nitrophenol
B. Phenol
C. m-Nitrophenol
D. p-Cresol

Explanation

To determine which phenol has the highest pKa value, we need to analyze the acidic strength of different phenolic compounds. The pKa value is inversely related to acidity; a higher pKa value indicates a weaker acid.

### Step-by-Step Solution:

1. **Understanding pKa and Acidity**:
- Recall that pKa is a measure of the acidity of a compound. A higher pKa value means that the compound is a weaker acid.
- The relationship is such that stronger acids have lower pKa values, while weaker acids have higher pKa values.

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