Unless the -OH group is converted into
a better leaving group, then alcohols are
poor substrates for substitution reactions.
Protonation to convert the leaving group into H2O
has limited utility as not all substrates or nucleophiles can be utilised
under acidic conditions without unwanted side reactions.
An alternative is to convert the alcohol into a tosylate,
which has a much better leaving group and will react with nucleophiles without
the need for the acid.
