Arrange the following in decreasing order of acidity : phenol and the ortho (I), meta (II) and para (III) cresols.
(I)
(II)
(III)
(IV)

Question

Arrange the following in decreasing order of acidity : phenol and the ortho (I), meta (II) and para (III) cresols. (I) (II) (III) (IV)

TestHub · Accepted Answer

Here (IV) is phenol. CH₃ donates electrons (+I and hyperconjugation) and destabilises the phenoxide ion, so each cresol is less acidic than phenol.

The meta isomer has only the weak +I effect, so it is the most acidic of the three. The +I effect is stronger at ortho than at para.

Order : IV $>$ II $>$ III $>$ I (pKa 9.99, 10.09, 10.26, 10.29).

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