|Solubility in water||decompose|
|Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)|
Methylenetriphenylphosphorane is an organophosphorus compound with the formula Ph3PCH2. It is the parent member of the phosphorus ylides, popularly known as Wittig reagents. It is a highly polar, highly basic species.
Preparation and use
- Ph3PCH3Br + BuLi → Ph3PCH2 + LiBr + BuH
The compound is generally not isolated, instead it is used in situ.
Methylenetriphenylphosphorane is used to replace oxygen centres in aldehydes and ketones with a methylene group:
- R2CO + Ph3PCH2 → R2C=CH2 + Ph3PO
The phosphorus-containing product is triphenylphosphine oxide.
Crystallographic characterization of the colourless ylide reveals that the phosphorus is approximately tetrahedral. The PCH2 centre is planar and the P=CH2 distance is 1.661 Å, which is much shorter than the P-Ph distances (1.823 Å). The compound is usually described as a combination of two resonance structures:
- Ph3P+CH2- ↔ Ph3P=CH2