15-Crown-5 is used as an efficient phase transfer catalyst and as a complexing agent. It is used to isolate oxonium ion (HO) salts especially from a solution of tetrchloroauric acid. It catalyzes the O-alkylation of the sodium salts of carboxylic acids in the penicillin and cephalosporin series, thereby facilitating esterification reaction without usage of acid. It is also used to facilitate the Williamson synthesis of ethers with hindered alcohols and sodium hydride. It is used with lithium aluminum hydride, for performing reduction reactions in hydrocarbon solvents. Further, it is involved in the Horner-Wadsworth-Emmons reaction to prepare stilbenes from aldehydes.
