Vinyl group
In chemistry, vinyl or ethenyl[1] (abbreviated as Vi[2]) is the functional group with the formula −CH=CH2. It is the ethylene (IUPAC ethene) molecule (H2C=CH2) less one hydrogen atom. The name is also used for any compound containing that group, namely R−CH=CH2 where R is any other group of atoms.
An industrially important example is vinyl chloride, precursor to PVC, a plastic commonly known as vinyl.
Vinyl is one of the alkenyl functional groups. On a carbon skeleton, sp2-hybridized carbons or positions are often called vinylic. Allyls, acrylates and styrenics contain vinyl groups. (A styrenic crosslinker with two vinyl groups is called divinyl benzene.)
Vinyl polymers[edit]
Vinyl groups can polymerize with the aid of a radical initiator or a catalyst, forming vinyl polymers. Vinyl polymers contain no vinyl groups. Instead they are saturated. The following table gives some examples of vinyl polymers.
| Monomer example | Example of resulting polymer |
|---|---|
| Vinyl chloride | Polyvinyl chloride (PVC) |
| Vinyl fluoride | Polyvinyl fluoride (PVF) |
| Vinyl acetate | Polyvinyl acetate (PVAc) |
Many vinylidene and vinylene compounds polymerize in the same manner. Those polymers are analogously referred to as polyvinylidenes and polyvinylenes, reflecting the monomeric precursors.
Reactivity[edit]
Vinyl derivatives are alkenes. If activated by an adjacent group, the increased polarization of the bond gives rise to characteristic reactivity, which is termed vinylogous:
- In allyl compounds, where the next carbon is saturated but substituted once, allylic rearrangement and related reactions are observed.
- Allyl Grignard reagents (organomagnesiums) can attack with the vinyl end first.
- If next to an electron-withdrawing group, conjugate addition (Michael addition) occurs.
Vinyl organometallics, e.g. vinyl lithium, participate in coupling reactions such as in Negishi coupling.
Etymology[edit]
The etymology of vinyl is the Latin vinum = "wine", because of its relationship with alcohol (in its original sense of ethyl alcohol). The term "vinyl" was coined by the German chemist Hermann Kolbe in 1851.[3]