# Tag Info

If you think about protonating 1-propyne on the terminal acetylenic carbon, you get a vinylic cation that could apparently form an allylic cation by a hydride shift. The bond to the hydride that would shift has to be lined up with the empty orbital to which it is migrating. So far, no problem. But after the shift, the empty $\mathrm{2p}$ orbital of the new ...