What Is A Vinyl Carbocation

A vinyl cation is a positively charged molecule a cation where the positive charge is located on a vinyl group ch ch2.

What is a vinyl carbocation.

A carbocation ˌ k ɑːr b oʊ ˈ k æ t aɪ ə n is an ion with a positively charged carbon atom among the simplest examples are the methenium ch 3 methanium ch 5 and vinyl c 2 h 3 cations. See also primary allylic carbocation secondary allylic carbocation tertiary allylic carbocation. The vinyl cation is a carbocation with the positive charge on an alkene carbon. Allylic carbon meaning the double bonded carbon atoms can be classified as vinylic and allylic carbon atoms.

Vinyl indicates the ch ch 2 functional group which can be formed by removing hydrogen from ethylene molecule. Carbon with two other atoms attached prefers sp hybridization and a linear geometry. A simple allylic system will have just one pi bond. Therefore the general molecular formula of vinyl compounds is r ch ch 2 where r is any other group of atoms.

The lightest allylic carbocation 1 is called the allyl carbocation. The rate of this step and therefore the rate of the overall substitution reaction depends on the activation energy for the process in which the bond between the carbon and the leaving group breaks and a carbocation forms. Since both carbon atoms form a double covalent bond so both are sp 2 hybridized. The general formula for vinyl group is r ch ch 2 in which both carbon atoms are bonded with double bond and r is attached at vinylic position.

Stability of carbocation intermediates. Allylic carbocations are able to share their burden of charge with a nearby group through resonance. 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. Occasionally carbocations that bear more than one positively charged carbon atom are also encountered e g ethylene dication c 2 h 2 4.

This is very very unstable and ranks under a methyl carbocation in stability. Acid catalyzed hydration of phenyl acetylene a terminal alkyne involves a vinylic carbocation intermediate. An allylic carbocation is a resonance stabilized carbocation in each of the two resonance forms of which the formal charge of 1 is on an allylic carbon. The hybridization of a vinyl carbocation is sp hybirdized.

A vinyl carbocation has a positive charge on the same carbon as the double bond. The vinyl carbocation a primary carbocation.