The reaction you are referring to is the nucleophilic substitution of bromine with a hydroxide ion in an acidic medium. This reaction can be represented as:R-Br + OH- R-OH + Br-In an acidic medium, the reaction mechanism is typically an S_N1 Substitution Nucleophilic Unimolecular or S_N2 Substitution Nucleophilic Bimolecular process, depending on the substrate and reaction conditions.1. S_N1 mechanism:Step 1: Protonation of the hydroxide ion by the acidic medium:OH- + H+ H2OStep 2: Formation of a carbocation intermediate:R-Br R+ + Br-Step 3: Nucleophilic attack by water since OH- is protonated to H2O in an acidic medium :R+ + H2O R-OH2+Step 4: Deprotonation of the intermediate to form the alcohol product:R-OH2+ + Br- R-OH + HBrIn the S_N1 mechanism, the intermediate formed is a carbocation, which is stabilized by resonance or inductive effects. The role of this intermediate is to allow the nucleophile water in this case to attack the positively charged carbon center, leading to the formation of the alcohol product.2. S_N2 mechanism:Step 1: Protonation of the hydroxide ion by the acidic medium:OH- + H+ H2OStep 2: Nucleophilic attack by water since OH- is protonated to H2O in an acidic medium and simultaneous leaving of the bromide ion:R-Br + H2O R-OH2+ + Br-Step 3: Deprotonation of the intermediate to form the alcohol product:R-OH2+ + Br- R-OH + HBrIn the S_N2 mechanism, there is no intermediate carbocation formed. Instead, the reaction proceeds through a concerted process where the nucleophile attacks the substrate while the leaving group departs simultaneously. The role of the intermediate R-OH2+ in this case is to facilitate the transfer of the proton from the nucleophile to the leaving group, resulting in the formation of the alcohol product.In both mechanisms, the intermediate plays a crucial role in the formation of the final alcohol product. The specific mechanism S_N1 or S_N2 depends on the substrate's structure, steric hindrance, and reaction conditions.