Question

Why is phenoxide more stable than phenol?

Answer 1

It isn't! Phenol is more stable than phenoxide ion.

Consider the equilibrium between the two species:

`"C"_6"H"_5"OH(aq)" +"H"_2"O(l)" ⇌ "C"_6"H"_5"O"^"-""(aq)" + "H"_3"O"^"+""(aq)"`

You would expect two oppositely charged ions to attract and neutralize each other, if possible.

Thus, phenol is more stable than phenoxide ion.

The equilibrium constant, `K_text(a) = 1.6 × 10^"-10"`.

This shows that the position of equilibrium lies far to the left.

The `K_text(a)` value corresponds to a free energy difference of `55.9 color(white)(l) "kJ·mol"^"-1"`.