Question

Give two reactions that show the acidic nature of phenol. Compare acidity of phenol with that of ethanol.

Answer 1

Hint: To solve this problem, firstly we should understand about acidity and other properties of phenol including the reactions (as asked in the question). And then we will compare the acidity and other properties of phenol with ethanol and hence approaching our solution.

Complete step by step answer:
- Acidity: It is the amount of acid in a substance. An acid is a chemical that gives out hydrogen ions in water forming salts by combining with metals. Acidity is measured on a scale called the pH scale called the pH scale. On this scale, a pH value of $7$ is neutral and pH value of less than $7$ shows increasing acidity.

- The acidic nature of phenol can be represented by these two reactions:Phenol reacts with sodium to give out sodium phenoxide, liberating ${H_2}$ gas
${C_6}{H_6}OH + Na \to {C_6}{H_5} - ONa + \dfrac{1}{2}{H_2}$
- Phenol reacts with sodium hydroxide giving out sodium phenoxide and water as by- products.
${C_6}{H_5} - OH + NaOH \to {C_6}{H_5} - ONa + {H_2}O$
- Now, when we talk about the comparison of the acidity of Phenol and Ethanol, the acidity of phenol is more than that of ethanol. The reason behind this is that the phenoxide ion gets stabilized due to resonance (due to delocalization over the ring) whereas ethoxide ion does not have that ring structure and hence, less stabilization due to resonance.
Hence, this is the reason for the greater acidity of phenol as compared to ethanol.

Note - Properties of phenol:
- Phenol is an organic compound sparingly soluble in water. Phenol is a weak acid in aqueous solution in the pH range 8-12. It is in equilibrium state with the phenolate anion.
- Phenol is more acidic than aliphatic compounds containing an $-OH$ Group is resonance stabilization of the phenoxide anion by the aromatic ring.
Uses -The major uses of phenol, consuming two third of its production, involve its conversion to precursors for plastics, condensation with acetone give, a key precursor to polycarbonates and epoxide resins.