Question

What is an example of an alkene that would react with water to make only one possible alcohol. Why can't your alkene make two different alcohols?

Answer 1

Any symmetric straight-chained alkene. If you wanted to guarantee it, go with a trans symmetric straight-chained alkene. So, ethene, 2-butene, 3-hexene, 4-octene, and so on would work. As long as the double bond is across carbon `n/2` and carbon `n/2+1` for a given alkene with `n` number of carbons.

That is because the same number of carbons separate the terminal carbon from one of the carbons that makes up the double bond in the alkene.

Try protonating any of the above alkenes.

It will not matter which carbon you choose, as either one has a similarly stable carbocation intermediate, and either one has that electropositive carbon the same number of carbons away from a given terminal carbon.

Hence, if the hydration product is rotated `180^@` in the plane of the screen/paper, you will get the same product back. Try it!