page_title: Phosphaalkyne
section_title: Elimination of hydrogen halides
hierarchical_section_title: Phosphaalkyne / Synthesis / By elimination reactions / Elimination of hydrogen halides
caption_attribution_description: English: Synthesis of substituted phosphaalkynes by the elimination of hydrogen chloride
context_page_description: In chemistry, a phosphaalkyne is an organophosphorus compound containing a triple bond between phosphorus and carbon with the general formula R-C≡P. Phosphaalkynes are the heavier congeners of nitriles, though, due to the similar electronegativities of phosphorus and carbon, possess reactivity patterns reminiscent of alkynes. Due to their high reactivity, phosphaalkynes are not found naturally on earth, but the simplest phosphaalkyne, phosphaethyne has been observed in the interstellar medium.
context_section_description: Following the initial synthesis of phosphaethyne, it was realized that the same compound can be prepared more expeditiously via the flash pyrolysis of methyldichlorophosphine (CH₃PCl₂), resulting in the loss of two equivalents of hydrogen chloride. This methodology has been utilized to synthesize numerous substituted phosphaalkynes, including the methyl, vinyl, chloride, and fluoride derivatives. Fluoromethylidynephosphane (F-C≡P) can also be prepared via the potassium hydroxide promoted dehydrofluorination of trifluoromethylphosphine (CF₃PH₂). It is speculated that these reactions generally proceed via an intermediate phosphaethylene with general structure RClC=PH. This hypothesis has found experimental support in the observation of F₂C=PH by ³¹P NMR spectroscopy during the synthesis of F-C≡P.
caption: Synthesis of substituted phosphaalkynes by flash pyrolysis of substituted dichloromethylphosphines. Here, R = CH3, CH=CH2, Cl, or F.