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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, or halide group). These cations have tetrahedral structures.
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 .
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.
A variety of phosphonium salts can be prepared by alkylation and arylation of organophosphines: PR 3 + R'X → [PR 3 R' +]X −. The methylation of triphenylphosphine is the first step in the preparation of the Wittig reagent.
It is the bromide salt of a phosphonium cation. It is a white salt that is soluble in polar organic solvents. Synthesis and reactions ...
Stereochemical experiments on cyclic phosphites have revealed the presence of both pentavalent phosphoranes and tetravalent phosphonium intermediates in chemical equilibrium being involved in the dealkylation step of the reaction using 31 P NMR. The decomposition of these intermediates is driven primarily by the nucleophilicity of the anion.
The structure of this salt is [PPh 4] + Cl −.It consists of tetraphenylphosphonium cations [PPh 4] + and chloride anions Cl −.The [PPh 4] + cation is tetrahedral.. PPh 4 Cl crystallises as the anhydrous salt, [2] which is the normal item of commerce, as well as a monohydrate [3] and a dihydrate.
In contrast to phosphonium ylides used in the Wittig reaction, phosphonate-stabilized carbanions are more nucleophilic but less basic. Likewise, phosphonate-stabilized carbanions can be alkylated. Unlike phosphonium ylides, the dialkylphosphate salt byproduct is easily removed by aqueous extraction. Several reviews have been published.