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Structure of the allyl group. In organic chemistry, an allyl group is a substituent with the structural formula −CH 2 −HC=CH 2.It consists of a methylene bridge (−CH 2 −) attached to a vinyl group (−CH=CH 2).
In organic chemistry, a vinyl group (abbr. Vi; [1] IUPAC name: ethenyl group [2]) is a functional group with the formula −CH=CH 2. It is the ethylene (IUPAC name: ethene) molecule ( H 2 C=CH 2 ) with one fewer hydrogen atom.
Vinyl cations were first proposed in 1944 as a reactive intermediate for the acid-catalyzed hydrolysis of alkoxyacetylenes to give alkyl acetate. [5] In the first step of their facile hydration reaction, which was the rate limiting step, a vinyl cation reactive intermediate was proposed; the positive charge was believed to formally lie on a ...
Electrophilic additions to allyl- and vinylsilanes take advantage of this, and site selectivity generally reflects this property—electrophiles become bound to the carbon γ to the silyl group. The electron-donating strength of the carbon-silicon bond is similar to that of an acetamide substituent and equal to roughly two alkyl groups. [6]
A solution of a carbonyl compound is added to a Grignard reagent. (See gallery) An example of a Grignard reaction (R 2 or R 3 could be hydrogen). The Grignard reaction (French:) is an organometallic chemical reaction in which, according to the classical definition, carbon alkyl, allyl, vinyl, or aryl magnesium halides (Grignard reagent) are added to the carbonyl groups of either an aldehyde or ...
β-Hydride elimination is a reaction in which a metal-alkyl centre is converted into the corresponding metal-hydride-alkene. [1] β-Hydride elimination can also occur for many alkoxide complexes as well. The main requirements are that the alkyl group possess a C-H bond β to the metal and that the metal be coordinatively unsaturated.
Lithium–halogen exchange is frequently used to prepare vinyl-, aryl- and primary alkyllithium reagents. Vinyl halides usually undergo lithium–halogen exchange with retention of the stereochemistry of the double bond. [2] The presence of alkoxyl or related chelating groups accelerates lithium–halogen exchange. [3]
The migratory ability is ranked tertiary > secondary > aryl > primary. [7] Allylic groups are more apt to migrate than primary alkyl groups but less so than secondary alkyl groups. [5] Electron-withdrawing groups on the substituent decrease the rate of migration. [8] There are two explanations for this trend in migration ability. [9]