Final answer:
When molecular halogen is added to water, it reacts to form hypohalous and hydrohalic acids, and with the addition of a base, salt solutions. Water also facilitates nucleophilic substitution by converting –OH to a better leaving group with the help of a strong acid. Furthermore, water can act as a nucleophile in certain reactions and dissolve ionic compounds by disrupting their ionic bonds.
Step-by-step explanation:
When a molecular halogen is added to a nucleophilic solvent like water, several reactions can occur. Molecular halogens can react with water to form hypohalous and hydrohalic acids, although not to completion, resulting in a mixture of the halogen and the respective acids. For example, the reactions of chlorine and bromine with water are analogous to fluorine with ice, resulting in a mixture of the halogen and the corresponding hypohalous and hydrohalic acids. In the presence of a base, these reactions can further produce solutions of salts.
Additionally, the addition of a strong acid like sulfuric acid to water can make the –OH group a better leaving group, thereby facilitating nucleophilic substitution reactions. Polar protic solvents like water solvate both cations and anions, which can affect dissociation and reaction mechanisms such as SN1 or hydration of alkenes, where water acts as a nucleophile. Ionic compounds like NaCl dissociate in water as the polar water molecules disrupt the ionic bonds and form spheres of hydration around the ions.