Vinylic Carbocation Definition

An allylic carbon is an sp3 carbon that is adjacent to a vinylic carbon.

Vinylic carbocation definition.

Formerly it was known as carbonium ion. Any trivalent disubstituted carbon is generally a vinylic carbocation in which the carbon atom which is bearing the positive charge is found to be double bonded and will always exist as sp hybridized. A vinylic carbocation which has an empirical formula of c h is a carbocation that has a positive charge only on the alkene carbon atom. In the absence of geometric constraints most substituted vinyl cations carry the formal positive charge on an sp hydridized carbon atom of linear geometry.

For a positive center to be attached to a more electronegative group is destabilizing. An allylic carbocation in which an allylic carbon bears the positive charge. Its empirical formula is c 2h 3. In the first mechanism step the alkyne is protonated by hydronium ion a strong acid to produce a resonance stabilized secondary vinylic carbocation shown in red.

Acid catalyzed hydration of phenyl acetylene a terminal alkyne involves a vinylic carbocation intermediate. Any of various compounds containing the vinyl group typically highly reactive easily polymerized and used as basic materials for plastics. Atoms or groups attached to an allylic carbon are termed allylic substituents. Look at the figure below notice that in the alkyl carbocation on the left the cationic center is attached to an s p x 3 carbon whereas in the vinylic cation in the middle the cationic center is attached to a more electronegative s p x 2 carbon.

A carbocation with a two coordinate positive carbon derived from formal removal of a hydride ion h from an alkene is known as a vinyl cation. The univalent hydrocarbon group ch 2 ch derived from ethylene. The vinyl cation is a carbocation with the positive charge on an alkene carbon. Carbocation today is defined as any even electron cation that possesses a significant positive charge on the carbon atom.