Phosphaalkene on:
[Wikipedia]
[Google]
[Amazon]
Phosphaalkenes ( IUPAC name: alkylidenephosphanes) are
Phosphaalkenes ( IUPAC name: alkylidenephosphanes) are organophosphorus compound
Organophosphorus compounds 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 in ...
s with double bonds between carbon and phosphorus(III) with the formula
In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwee ...
R2C=PR. In the compound phosphorine
Phosphorine ( IUPAC name: phosphinine) is a heavier element analog of pyridine, containing a phosphorus atom instead of an aza- moiety. It is also called phosphabenzene and belongs to the phosphaalkene class. It is a colorless liquid that is ...
one carbon atom in benzene is replaced by phosphorus. The reactivity of phosphaalkenes is often compared to that of alkenes and not to that of imines because the HOMO of phosphaalkenes is not the phosphorus lone pair
In chemistry, a lone pair refers to a pair of valence electrons that are not shared with another atom in a covalent bondIUPAC ''Gold Book'' definition''lone (electron) pair''/ref> and is sometimes called an unshared pair or non-bonding pair. Lone ...
(as in imines the amine lone pair) but the double bond. Therefore like alkenes, phosphaalkenes engage in Wittig reactions, Peterson reactions, Cope rearrangements and Diels-Alder reactions.
The first phosphaalkene discovered was a phosphabenzene, by Mërkl in 1969. The first localized phosphaalkene was reported in 1976 by Gerd Becker as a keto-enol tautomerism akin a Brook rearrangement:
::
In the same year Harold Kroto established spectroscopically that thermolysis of Me2PH generates CH2=PMe. A general method for the synthesis of phosphaalkenes is by 1,2-elimination
An elimination reaction is a type of organic reaction in which two substituents are removed from a molecule in either a one- or two-step mechanism. The one-step mechanism is known as the E2 reaction, and the two-step mechanism is known as the E1 r ...
of suitable precursors, initiated thermally or by base such as DBU, DABCO or triethylamine:
::
The Becker method is used in the synthesis of the phosphorus pendant of Poly(p-phenylene vinylene):''Phosphorus Copies of PPV: π-Conjugated Polymers and Molecules Composed of Alternating Phenylene and Phosphaalkene Moieties'' Vincent A. Wright, Brian O. Patrick, Celine Schneider, and Derek P. Gates J. Am. Chem. Soc.; 2006; 128(27) pp 8836 - 8844; (Article) {{doi, 10.1021/ja060816l
::.
The reduction or oxidation of phosphaalynes can produce radical phosphorus ions.
References