Chemistry - GOC Question with Solution | TestHub

In (a) the positive carbon is the end of a C-C triple bond. It has no alkyl or alkenyl group to donate electrons, and its empty orbital sits on a very electronegative sp carbon with a very high s character, so it is a very unstable cation. The vinyl cation (b) has a CH₂ group on the other carbon and is more stable. a $<$ b.