Vinylic Carbocation Definition

Acid catalyzed hydration of phenyl acetylene a terminal alkyne involves a vinylic carbocation intermediate.

Vinylic carbocation definition.

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 vinyl cation is a carbocation with the positive charge on an alkene carbon. Formerly it was known as carbonium ion. Any of various compounds containing the vinyl group typically highly reactive easily polymerized and used as basic materials for plastics.

Carbocation today is defined as any even electron cation that possesses a significant positive charge on the 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. The univalent hydrocarbon group ch 2 ch derived from ethylene. 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.

An allylic carbocation in which an allylic carbon bears the positive charge. 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. An allylic carbon is an sp3 carbon that is adjacent to a vinylic carbon. We can basically say that they are carbon cations.

Atoms or groups attached to an allylic carbon are termed allylic substituents. 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. Its empirical formula is c 2h 3. A carbocation is a molecule in which a carbon atom has a positive charge and three bonds.