Video Transcript
In water, phenol will undergo the following reaction. What name is given to the anion? (A) Phenyl, (B) benzyl, (C) anilinium, (D) phenoxide, (E) hydroxide.
In the reaction provided, the reactants are phenol and water. A phenol molecule consists of a hydroxy group directly bonded to an aromatic ring. The products of the reaction are two different ions: an anion, which is a negatively charged ion, and a cation, which is a positively charged ion. When comparing the reactants to the products, we notice that the phenol molecule loses a hydrogen ion during the reaction, while water gains a hydrogen ion. According to the Brønsted–Lowry theory of acids and bases, an acid is a substance that can lose or donate H+ ions in a reaction and a base is a substance that can gain or accept H+ ions. Therefore in this reaction, phenol is the acid and water is the base. This is consistent with what we know about phenol as phenol is a weakly acidic substance.
In the reaction between phenol and water, a hydrogen ion is released from the hydroxy group of the phenol molecule. This hydrogen ion is then gained by a water molecule, which converts the water molecule to the H3O+ ion. The name of the H3O+ ion is the hydronium ion. And of the name of the ion that is left behind after phenol loses a hydrogen ion is the phenoxide ion. The phen- or P-H-E-N part of the name comes from the original phenol molecule, while the oxide part of the name comes from the oxygen atom with a negative charge. In conclusion, the name given to the anion when phenol reacts with water is phenoxide, or answer choice (D).
