Following the initial synthesis of phosphaethyne, it was realized that the same compound can be prepared more expeditiously via the flash pyrolysis of methyldichlorophosphine (CHPCl), 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 (CFPH). 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 FC=PH by P NMR spectroscopy during the synthesis of F-C≡P.