Acid catalyzed hydration of phenyl acetylene a terminal alkyne involves a vinylic carbocation intermediate.
A secondary vinylic carbocation is.
If in the more stable of the two resonance forms of an allylic carbocation the formal charge of 1 is on a secondary carbon the allylic carbocation is called a secondary 2 allylic carbocation.
Its empirical formula is c 2 h 3 more generally a vinylic cation is any disubstituted trivalent carbon where the carbon bearing the positive charge is part of a double bond and is sp hybridized in the chemical literature substituted vinylic cations are often referred to as vinyl cations and understood to.
The allylic position is also like a vinylic position.
The more substituted a carbocation is the more stable it is.
This carbocation is also a benzylic carbocation.
If in both resonance forms the formal charge of 1 is on a secondary carbon it also is a secondary allylic carbocation.
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.
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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.
Secondary carbocations will require more energy than tertiary and primary carbocations will require the most energy.
Since both carbon atoms form a double covalent bond so both are sp 2 hybridized.
The vinyl cation is a carbocation with the positive charge on an alkene carbon.