The acidity of a phenol molecule is determined by the ease with which it can lose a proton H+ from its hydroxyl group, forming a phenoxide ion. The stability of the phenoxide ion plays a crucial role in determining the acidity of the phenol. The more stable the phenoxide ion, the more acidic the phenol.When comparing a monohydroxy phenol to a dihydroxy phenol, the presence of additional hydroxyl groups can have a significant impact on the acidity of the molecule. This is primarily due to the electron-withdrawing effect of the hydroxyl groups, which can stabilize the phenoxide ion through resonance and inductive effects.Let's consider the following chemical equations for the ionization of monohydroxy phenol phenol and dihydroxy phenol catechol in water:1. Phenol: C6H5OH + H2O C6H5O- + H3O+2. Catechol 1,2-dihydroxybenzene : C6H4 OH 2 + H2O C6H3 OH O- + H3O+In the case of monohydroxy phenol phenol , the phenoxide ion C6H5O- is formed upon deprotonation. The negative charge on the oxygen atom is delocalized through resonance within the benzene ring, providing some stabilization to the phenoxide ion.However, in the case of dihydroxy phenol catechol , the presence of an additional hydroxyl group further stabilizes the phenoxide ion C6H3 OH O- through resonance. The negative charge on the oxygen atom can be delocalized not only within the benzene ring but also between the two oxygen atoms of the hydroxyl groups. This increased stabilization of the phenoxide ion makes it easier for catechol to lose a proton, making it more acidic than phenol.In summary, the presence of additional hydroxyl groups in a phenol molecule increases its acidity due to the enhanced stabilization of the phenoxide ion through resonance and inductive effects. As a result, dihydroxy phenols like catechol are more acidic than monohydroxy phenols like phenol.