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Phosphonium ion Structure of PH + 4, the parent phosphonium cation. In chemistry, the term phosphonium (more obscurely: phosphinium) describes polyatomic cations with the chemical formula PR + 4 (where R is a hydrogen or an alkyl, aryl, organyl or halogen group). These cations have tetrahedral structures.
Tetraphenylphosphonium chloride is the chemical compound with the formula [(C 6 H 5) 4 P]Cl, abbreviated Ph 4 PCl or PPh 4 Cl or [PPh 4]Cl, where Ph stands for phenyl. Tetraphenylphosphonium and especially tetraphenylarsonium salts were formerly of interest in gravimetric analysis of perchlorate and related oxyanions.
According to X-ray crystallography, [(i-Pr 2 N) 2 P] + is nearly planar consistent with sp 2-hybridized phosphorus center. [6] The planarity of the nitrogen center is consistent with the resonance of the lone pair of the nitrogen atom as a pi bond to the empty phosphorus 3p orbital perpendicular to the N−P−N plane.
Most processes begin with phosphorous acid (aka phosphonic acid, H 3 PO 3), exploiting its reactive P−H bond. [1] [3]Phosphonic acid can be alkylated via the Kabachnik–Fields reaction or Pudovik reaction to give aminophosphonate, which are useful as chelating agents.
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Because phosphonium ylides are seldom isolated, the byproduct(s) generated upon deprotonation essentially plays the role of an additive in a Wittig reaction. As a result, the choice of base has a strong influence on the efficiency and, when applicable, the stereochemical outcome of the Wittig reaction.
Phosphonium iodide is a powerful substitution reagent in organic chemistry; for example, it can convert a pyrilium into a phosphinine via substitution. [3] In 1951, Glenn Halstead Brown found that PH 4 I reacts with acetyl chloride to produce an unknown phosphine derivative, possibly CH 3 C(=PH)PH 2 ·HI .
BOP (benzotriazol-1-yloxytris(dimethylamino)phosphonium hexafluorophosphate) is a reagent commonly used for the synthesis of amides from carboxylic acids and amines in peptide synthesis.