Methylenetriphenylphosphorane

Last updated
Methylenetriphenylphosphorane
Ph3P=CH2-ylid-phosphorane-resonance-2D.png
Ph3P=CH2-from-xtal-1989-3D-balls.png
Names
Preferred IUPAC name
Methylidenetri(phenyl)phosphane
Identifiers
3D model (JSmol)
ChemSpider
PubChem CID
UNII
  • InChI=1S/C19H17P/c1-20(17-11-5-2-6-12-17,18-13-7-3-8-14-18)19-15-9-4-10-16-19/h2-16H,1H2
    Key: XYDYWTJEGDZLTH-UHFFFAOYSA-N
  • InChI=1/C19H17P/c1-20(17-11-5-2-6-12-17,18-13-7-3-8-14-18)19-15-9-4-10-16-19/h2-16H,1H2
    Key: XYDYWTJEGDZLTH-UHFFFAOYAU
  • C=P(C1=CC=CC=C1)(C2=CC=CC=C2)C3=CC=CC=C3
Properties
C19H17P
Appearanceyellow solid
Density 1.19 g/cm3
decompose
Solubility THF
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 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.

Contents

Preparation and use

Methylenetriphenylphosphorane is prepared from methyltriphenylphosphonium bromide by its deprotonation using a strong base like butyllithium: [1]

Ph3PCH3Br + BuLi → Ph3PCH2 + LiBr + BuH

The phosphorane is generally not isolated, instead it is used in situ. The estimated pKa of this carbon acid is near 15. [2] Potassium tert-butoxide has been used in place of butyl lithium. [3] Sodium amide has also been used a base. [4]

Methylenetriphenylphosphorane is used to replace oxygen centres in aldehydes and ketones with a methylene group, i.e., a methylenation:

R2CO + Ph3PCH2 → R2C=CH2 + Ph3PO

The phosphorus-containing product is triphenylphosphine oxide.

Structure

Crystallographic characterization of the colourless ylide reveals that the phosphorus atom 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). [5] The compound is usually described as a combination of two resonance structures:

Ph3P+CH2 ↔ Ph3P=CH2

Uses

Two examples of the Wittig reaction using methylenetriphenylphosphorane Wittig CH2 examples.png
Two examples of the Wittig reaction using methylenetriphenylphosphorane

Methylenetriphenylphosphorane has become a standard tool for synthetic organic chemists. [6]

Related Research Articles

An ylide or ylid is a neutral dipolar molecule containing a formally negatively charged atom (usually a carbanion) directly attached to a heteroatom with a formal positive charge (usually nitrogen, phosphorus or sulfur), and in which both atoms have full octets of electrons. The result can be viewed as a structure in which two adjacent atoms are connected by both a covalent and an ionic bond; normally written X+–Y. Ylides are thus 1,2-dipolar compounds, and a subclass of zwitterions. They appear in organic chemistry as reagents or reactive intermediates.

<span class="mw-page-title-main">Phosphonium</span> Family of polyatomic cations containing phosphorus

In chemistry, the term phosphonium describes polyatomic cations with the chemical formula PR+
4
. These cations have tetrahedral structures. The salts are generally colorless or take the color of the anions.

<span class="mw-page-title-main">Triphenylphosphine</span> Chemical compound

Triphenylphosphine (IUPAC name: triphenylphosphane) is a common organophosphorus compound with the formula P(C6H5)3 and often abbreviated to PPh3 or Ph3P. It is versatile compound that is widely used as a reagent in organic synthesis and as a ligand for transition metal complexes, including ones that serve as catalysts in organometallic chemistry. PPh3 exists as relatively air stable, colorless crystals at room temperature. It dissolves in non-polar organic solvents such as benzene and diethyl ether.

The Wittig reaction or Wittig olefination is a chemical reaction of an aldehyde or ketone with a triphenyl phosphonium ylide called a Wittig reagent. Wittig reactions are most commonly used to convert aldehydes and ketones to alkenes. Most often, the Wittig reaction is used to introduce a methylene group using methylenetriphenylphosphorane (Ph3P=CH2). Using this reagent, even a sterically hindered ketone such as camphor can be converted to its methylene derivative.

<span class="mw-page-title-main">Johnson–Corey–Chaykovsky reaction</span> Chemical reaction in organic chemistry

The Johnson–Corey–Chaykovsky reaction is a chemical reaction used in organic chemistry for the synthesis of epoxides, aziridines, and cyclopropanes. It was discovered in 1961 by A. William Johnson and developed significantly by E. J. Corey and Michael Chaykovsky. The reaction involves addition of a sulfur ylide to a ketone, aldehyde, imine, or enone to produce the corresponding 3-membered ring. The reaction is diastereoselective favoring trans substitution in the product regardless of the initial stereochemistry. The synthesis of epoxides via this method serves as an important retrosynthetic alternative to the traditional epoxidation reactions of olefins.

<span class="mw-page-title-main">Phosphoranes</span>

A phosphorane (IUPAC name: λ5-phosphane) is a functional group in organophosphorus chemistry with pentavalent phosphorus. Phosphoranes have the general formula PR5.

The Horner–Wadsworth–Emmons (HWE) reaction is a chemical reaction used in organic chemistry of stabilized phosphonate carbanions with aldehydes to produce predominantly E-alkenes.

Organophosphorus chemistry is the scientific study of the synthesis and properties of organophosphorus compounds, which are organic compounds containing phosphorus. They are used primarily in pest control as an alternative to chlorinated hydrocarbons that persist in the environment. Some organophosphorus compounds are highly effective insecticides, although some are extremely toxic to humans, including sarin and VX nerve agents.

Phosphazenes refer to classes of organophosphorus compounds featuring phosphorus(V) with a double bond between P and N. One class of phosphazenes have the formula R−N=P(−NR2)3. These phosphazenes are also known as iminophosphoranes and phosphine imides. They are superbases. Another class of compounds called phosphazenes are represented with the formula (−N=P 2−)n, where X = halogen, alkoxy group, amide and other organyl groups. One example is hexachlorocyclotriphosphazene (−N=P 2−)3. Bis(triphenylphosphine)iminium chloride [Ph3P=N=PPh3]+Clis also referred to as a phosphazene, where Ph = phenyl group. This article focuses on those phosphazenes with the formula R−N=P(−NR2)3.

<span class="mw-page-title-main">Iminophosphorane</span>

Iminophosphorane is a kind of organophosphorus compound with the formula R3PNR'. Like the corresponding phosphine oxides and Wittig reagents, iminophosphoranes are ylides. Their bonding is described by two resonance structures.

<span class="mw-page-title-main">Diphenylphosphine</span> Chemical compound

Diphenylphosphine, also known as diphenylphosphane, is an organophosphorus compound with the formula (C6H5)2PH. This foul-smelling, colorless liquid is easily oxidized in air. It is a precursor to organophosphorus ligands for use as catalysts.

<span class="mw-page-title-main">Organosilver chemistry</span> Study of chemical compounds containing carbon-silver chemical bonds

Organosilver chemistry is the study of organometallic compounds containing a carbon to silver chemical bond. The theme is less developed than organocopper chemistry.

<span class="mw-page-title-main">Phosphinidene</span> Type of compound

Phosphinidenes are low-valent phosphorus compounds analogous to carbenes and nitrenes, having the general structure RP. The "free" form of these compounds is conventionally described as having a singly-coordinated phosphorus atom containing only 6 electrons in its valence level. Most phosphinidenes are highly reactive and short-lived, thereby complicating empirical studies on their chemical properties. In the last few decades, several strategies have been employed to stabilize phosphinidenes, and researchers have developed a number of reagents and systems that can generate and transfer phosphinidenes as reactive intermediates in the synthesis of various organophosphorus compounds.

Montréalone is a mesoionic heterocyclic chemical compound. It is named for the city of Montréal, Canada, which is the location of McGill University, where it was first discovered.

Hexaphenylcarbodiphosphorane is the organophosphorus compound with the formula C(PPh3)2 (where Ph = C6H5). It is a yellow, moisture-sensitive solid. The compound is classified as an ylide and as such carries significant negative charge on carbon. It is isoelectronic with bis(triphenylphosphine)iminium. The P-C-P angle is 131°. The compound has attracted attention as an unusual ligand in organometallic chemistry.

<span class="mw-page-title-main">Lanthanocene</span>

A lanthanocene is a type of metallocene compound that contains an element from the lanthanide series. The most common lanthanocene complexes contain two cyclopentadienyl anions and an X type ligand, usually hydride or alkyl ligand.

<span class="mw-page-title-main">Methyltriphenylphosphonium bromide</span> Chemical compound

Methyltriphenylphosphonium bromide is the organophosphorus compound with the formula [(C6H5)3PCH3]Br. It is the bromide salt of a phosphonium cation. It is a white salt that is soluble in polar organic solvents.

In organic chemistry, Wittig reagents are organophosphorus compounds of the formula R3P=CHR', where R is usually phenyl. They are used to convert ketones and aldehydes to alkenes:

In organic chemistry, methylenation is a chemical reaction that inserts a methylene group into a chemical compound:

1-Phosphaallenes is are allenes in which the first carbon atom is replaced by phosphorus, resulting in the structure: -P=C=C<.

References

  1. Wittig, Georg; Schoellkopf, U. (1960). "Methylenecyclohexane". Organic Syntheses. 40: 66. doi:10.15227/orgsyn.040.0066.
  2. Ling-Chung, Sim; Sales, Keith D.; Utley, James H. P. (1990). "Measurement of pKa Values for Phosphonium Salts via the Kinetics of Proton Transfer to an Electrogenerated Base". Journal of the Chemical Society, Chemical Communications (9): 662. doi:10.1039/C39900000662.
  3. Fitjer, L.; Quabeck, U. Synthetic Communications1985, 15(10), 855–864.
  4. F. A. Bottino, G. Di Pasquale, A. Pollicino, A. Recca and D. T. Clark (1990). "Synthesis of 2-(2-hydroxyphenyl)-2H-benzotriazole monomers and studies of the surface photostabilization of the related copolymers". Macromolecules . 23 (10): 2662–2666. Bibcode:1990MaMol..23.2662B. doi:10.1021/ma00212a011.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  5. Bart, J. C. J. (1969). "Structure of the non-stabilized phosphonium ylid methylenetriphenylphosphorane". Journal of the Chemical Society B. 1969: 350–365. doi:10.1039/J29690000350.
  6. B. E. Maryanoff & A. B. Reitz (1989). "The Wittig olefination reaction and modifications involving phosphoryl-stabilized carbanions. Stereochemistry, mechanism, and selected synthetic aspects". Chem. Rev. 89 (4): 863–927. doi:10.1021/cr00094a007.