Question

Which is a stronger acid – phenol or cresol? Give reason.

Hint:

Electron-donating groups like the methyl group in cresol reduce the acidity of phenols by stabilizing the negative charge on the oxygen less effectively.

Answer 1

Phenol is a stronger acid than cresol because cresol has a methyl group (\(-CH_3\)) attached to the aromatic ring. The methyl group is an electron-donating group, which increases the electron density on the ring and on the oxygen atom of the hydroxyl group. This reduces the ability of the oxygen atom to lose a proton, making cresol less acidic than phenol. In contrast, phenol’s hydroxyl group is less stabilized and more likely to lose a proton, making it more acidic.