question_answer

                                                                                     Why does pure HCN fail to react with aldehydes and ketones?

Answer:

                HCN is mainly a covalent compound and cannot provide \[C{{N}^{-}}\] ion readily for the nucleophilic attack on the carbonyl compound. The reaction is carried in the presence of base which helps in the ionisation of the acid to liberate \[C{{N}^{-}}\] ion. \[HCN+O{{H}^{-}}\,\xrightarrow{\,}\,{{H}_{2}}O+C{{N}^{-}}\]