Pentadecylmagnesium bromide is primarily used in organic synthesis as a Grignard reagent. It is employed to introduce the pentadecyl group into various organic molecules, facilitating the formation of carbon-carbon bonds. This reagent is particularly useful in the preparation of long-chain hydrocarbons, alcohols, and other complex organic compounds. It is also utilized in the synthesis of surfactants and lubricants, where the long alkyl chain contributes to the desired properties. Additionally, it finds application in the production of specialty chemicals and intermediates used in pharmaceuticals, agrochemicals, and materials science. Its reactivity with carbonyl compounds makes it valuable in the construction of complex molecular structures in research and industrial settings.