The rate of nucleophilic substitutions in alcohols is influenced by several key factors:
The nature of the leaving group ⇒ a good leaving group, such as a water molecule generated from an alcohol protonation, will facilitate the reaction.
The structure of the alcohol ⇒ primary alcohols undergo substitutions more slowly than secondary and tertiary alcohols due to the lower stability of the carbocation intermediate.
The strength and solvation of the nucleophile ⇒ stronger, less hindered nucleophiles tend to react faster, and polar aprotic solvents generally increase the rate by better solvating the cations without stabilizing anions, thus enhancing nucleophilicity.