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I have a question regarding the stability of carbocations. It is shown below.
I am confused between options II and III. The structure shown in option II has more resonance structures. Thus, I believe it should be more stable than that in option III. However, the given answer is option III.
Electronegativity of the atom which holds the positive charge is a dominating factor over resonance, in option 2, the positive charge is in an sp hybridized carbon atom which is more electronegative than th sp2 hybridized carbon atom on which the positive charge resides in option 3, and positive charge on more electronegative atom is very unstable. Hence 3 is way more stable than 2. Vinylic carbocations are very unstable and rarely encountered.
