# What is a phenoxide ion?

Apr 6, 2016

A phenoxide ion is the conjugate base of phenol. It looks like:

#### Explanation:

According to the Bronsted-Lowry theory of acids and bases, an acid is a molecule that donates ${H}^{+}$ ions, and a base is a molecule that takes them up again.

Taking the example of

$N {H}_{3} + {H}_{2} O \to N {H}_{4}^{+} + H {O}^{-}$

then $N {H}_{3}$ acts like a base and ${H}_{2} O$ acts like an acid, based on the Bronsted-Lowry definitions above.

This makes $N {H}_{4}^{+}$ into a conjugate acid (because it would, given the chance, give up hydrogen ions) and $H {O}^{-}$ the conjugate base (since it would now accept hydrogen).

Phenoxide is a conjugate base, which means it is formed from an acid that has given up its hydrogen. This acid is a phenol molecule, which is a benzene ring with a hydroxyl group. The hydrogen of the hydroxyl leaves, and an ${O}^{-}$ remains, forming the 'oxide ion' part of the phenoxide ion.

'Phenyl' is simply another systematic name for benzene, a ring of ${C}_{6} {H}_{6}$ with delocalised electrons. 'Phenol' is the alcohol form of benzene, because it has an $- O H$ or hydroxyl group.