If in both resonance forms the formal charge of 1 is on a secondary carbon it also is a secondary allylic carbocation.
A secondary vinylic carbocation is.
The more substituted a carbocation is the more stable it is.
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The more stable the carbocation the lower the activation energy for reaching that intermediate will be.
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.
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.
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.
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Since both carbon atoms form a double covalent bond so both are sp 2 hybridized.
The allylic position is also like a vinylic position.
The carbocation bonded to three alkanes tertiary carbocation is the most stable and thus the correct answer.
The vinyl cation is a carbocation with the positive charge on an alkene carbon.
Acid catalyzed hydration of phenyl acetylene a terminal alkyne involves a vinylic carbocation intermediate.