Why?

1. m-OCH₃–phenol

• At meta, +M cannot operate
• Only –I → acidity increases
• Highest

2. Phenol

• Reference compound.

3. m-CH₃–phenol

• Meta CH₃ → mainly +I
• Acidity decreases slightly.

4. p-CH₃ and o-CH₃

• CH₃ has +I and hyperconjugation
• Both decrease acidity.
• o-CH₃ has additional steric/proximity effects, making it generally less acidic.

5. p-OCH₃ and o-OCH₃

• At o/p, +M of –OCH₃ operates strongly
• This destabilizes phenoxide → acidity decreases considerably.
• Ortho also has proximity/steric effects.