- Source: Phosphonium iodide
Phosphonium iodide is a chemical compound with the formula PH4I. It is an example of a salt containing an unsubstituted phosphonium cation (PH+4). Phosphonium iodide is commonly used as storage for phosphine and as a reagent for substituting phosphorus into organic molecules.
Preparation
Phosphonium iodide is prepared by mixing diphosphorus tetraiodide (P2I4) with elemental phosphorus and water at 80 °C and allowing the salt to sublime.
10 P2I4 + 13 P4 + 128 H2O → 40 PH4I + 32 H3PO4
Properties
= Structure
=Its crystal structure has the tetragonal space group P4/nmm, which is a distorted version of the NH4Cl crystal structure; the unit cell has approximate dimensions 634×634×462 pm. The hydrogen bonding in the system causes the PH+4 cations to orient such that the hydrogen atoms point toward the I− anions.
= Chemical
=At 62 °C and atmospheric pressure, phosphonium iodide sublimates and dissociates reversibly into phosphine and hydrogen iodide (HI). It oxidizes slowly in air to give iodine and phosphorus oxides; it is hygroscopic and is hydrolyzed into phosphine and HI:
PH4I ⇌ PH3 + HI
Phosphine gas may be devolved from phosphonium iodide by mixing an aqueous solution with potassium hydroxide:
PH4I + KOH → PH3 + KI + H2O
It reacts with elemental iodine and bromine in a nonpolar solution to give phosphorus halides; for example:
2PH4I + 5I2 → P2I4 + 8HI
Phosphonium iodide is a powerful substitution reagent in organic chemistry; for example, it can convert a pyrilium into a phosphinine via substitution. In 1951, Glenn Halstead Brown found that PH4I reacts with acetyl chloride to produce an unknown phosphine derivative, possibly CH3C(=PH)PH2·HI.
References
Kata Kunci Pencarian:
- Phosphonium iodide
- Phosphonium
- Diphosphorus tetraiodide
- Cyclohexane
- Rudolph Schoenheimer
- Ammonium iodide
- Phosphine
- Wittig reaction
- Wittig reagents
- Methylcyclopentane
