What is Ylide?
A neutral dipolar molecule with a negatively charged atom immediately linked to a positively charged heteroatom, where the negatively charged atom is a nucleophilic core and the onium group is usually a suitable leaving group, is known as a ylide.
A ylide is a chemical molecule in which two neighbouring atoms have both a positive and a negative formal charge. One charge of phosphorus ylides is created at a time. The positive charge on phosphorus must first be organised into a phosphonium ion.
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Mononuclear Ylide Complexes
Ylides are compounds in which one atom has a positive charge while the other atom has a negative charge. They’re zwitterions, which are molecules containing both positive and negative charges in the same molecule.
Gold(I) and gold(III) mononuclear ylide complexes have been produced in a variety of ways. Gold(I) complexes can be charged or uncharged, and the second ligand can be a neutral donor ligand, another ylide moiety, a halide or pseudohalide, a carbanionic group, or a carbonyl metalate. Phosphorus ylides have been used to make the most gold(I) and gold(III) complexes, however species including arsenic or sulfoxonium ylides have also been identified.
Ylide Formation
P-d bonding has been observed to stabilise dipolar phosphorus compounds. Carbanions next to phosphonium centres benefit from this bonding stabilisation, and the zwitterionic conjugate bases generated from such cations are known as ylides. A compound with opposite charges on nearby atoms that both have complete octets is known as a ylide.
An organophosphorus ylide, commonly known as Wittig reagents, will be utilised in the Wittig process described below. Because phosphorus has the ability to store more than eight valence electrons, a resonance structure can be drawn, resulting in a double-bonded structure.
Although many ylides are commercially available, they are frequently needed to be synthesised. An alkyl halide and a trialkyl phosphine can be used to make ylides. Ylides are often made with triphenylphosphine. Because the ylide synthesis uses an SN2 reaction, methyl and primary halides perform well.
Ylide Examples
The Wittig reaction, which involves the addition of a phosphorus ylide to an aldehyde or ketone, is a classic example of a ylide addition to a carbonyl. Instead of producing alcohol, the reaction yields an alkene. The formation of a phosphorus oxide “side product” drives the reaction.
The Wittig reaction is an organic chemical reaction that produces an alkene and triphenylphosphine oxide by reacting an aldehyde or ketone with a Wittig reagent (a triphenyl phosphonium ylide). An organophosphorus ylide is referred to as a Wittig reagent. Ylides are compounds in which two neighbouring atoms have complete octet electronic configurations and opposing charges.
Ylides are a type of zwitterion, which are charged molecules with both positive and negative charges. An amino acid, which comprises a positive ammonium ion and a negative carboxylate ion in the same molecule, is arguably the most common example of a zwitterion.
Frequently Asked Questions on Ylide
What is a ylide in chemistry?
A ylide is defined as a neutral dipolar molecule containing a negatively charged atom directly attached to a positively charged heteroatom, in which the negatively charged atom is a nucleophilic centre and the onium group is usually a good leaving group.
What is phosphorus ylide?
Phosphorus ylides are 1,2-dipolar compounds with a negative charge on the carbon atom. Although the use of ylide substituents in main group chemistry is still in its infancy, the first examples of isolated compounds impressively demonstrate the potential of these ligands.
How phosphorus ylide is formed?
Phosphorus ylides are routinely generated by the deprotonation of phosphonium salts, themselves typically produced via quaternization of phosphine with an alkyl halide.
How are stabilised phosphorus ylides prepared?
Triphenylphosphine, dialkyl acetylene dicarboxylate, and acids such as phenols, imides, amides, enols, oximes and alcohols react with each other via a multicomponent reaction to produce stabilised phosphorus ylides.
What is a ylide used for?
Phosphonium ylides are used in the Wittig reaction, a method used to convert ketones and especially aldehydes to alkenes. The positive charge in these Wittig reagents is carried by a phosphorus atom with three phenyl substituents and a bond to a carbanion. Ylides can be ‘stabilised’ or ‘unstabilised’.
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