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A phosphonium salt is a salt containing the phosphonium (PH4+) ion such as phosphonium iodide (PH4+I−). More commonly, phosphonium refers to a quaternary organic derivative such as tetraphenylphosphonium chloride, (C6H5)4P+ Cl− and tetramethylphosphonium iodide, ==Use for preparation of Wittig reagents== Alkyltriphenylphosphonium salts are widely used for the preparation of Wittig reagents for the Wittig reaction. Such salts are readily made by the reaction of triphenylphosphine with an alkyl halide: : :''Note that Ph stands for phenyl and X is a halide'' The reaction works well if the alkyl group is methyl or an unhindered primary alkyl group (as shown), but it is usually poor with secondary alkyl halides. Tertiary alkyl groups cannot form the ylide. The phosphonium salt is a stable compound which can often be purified by recrystallisation from ethanol. To form the Wittig reagent (ylide), the phosphonium salt is suspended in a solvent such as diethyl ether or THF and a strong base such as phenyllithium or ''n''-butyllithium is added. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Phosphonium salt」の詳細全文を読む スポンサード リンク
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