Why does HF generate a carbocation with an alkene

Question

I was reading of different ways to perform Friedel Craft alkylations.

One of the methods I came across involved an alkene in the presence of H+ or a mineral acid like $\ce{HF}$. Here $\ce{H+}$ or $\ce{HF}$ caused an electromeric shift of the pi electrons and the $\ce{H+}$ bonded there resulting in a carbocation.

However I felt like the bond strength of $\ce{HF}$ is so high that it couldn't be possible to cleave it for the donation of $\ce{H+}$ (If that's what happens. Correct me if I'm wrong).

Why does it still generate a carbocation?

Well, it sure can do that if it's concentrated enough. Somewhat depending on alkene and temperature, though, I guess. — Mithoron, Jun 15 '20 at 19:34
You felt wrong. HF is a typical acid, behaves like an acid, and (most likely) tastes like an acid. — Ivan Neretin, Jun 15 '20 at 19:36
@IvanNeretin But HF is a really weak acid, owing to its extremely strong bond with hydrogen — Vamsi Krishna, Jun 15 '20 at 19:37
@Mithoron But what could cause the HF bond cleavage? Surely the pi electrons wouldnt suffice? — Vamsi Krishna, Jun 15 '20 at 19:38
https://chemistry.stackexchange.com/questions/34818/is-hf-the-least-acidic-hydrogen-halide/34829#34829 — Mithoron, Jun 15 '20 at 19:48
It's neither truly weak, nor typical. Diluted aq HF wouldn't do it, but pure could work wonders. — Mithoron, Jun 15 '20 at 19:50

score 4 · Accepted Answer · edited Jul 04 '20 at 16:03

However I felt like the bond strength of $\ce{HF}$ is so high that it couldn't be possible to cleave it for the donation of $\ce{H+}$

HF has the highest single bond energy and hence you were right in expecting that it may not dissociate.However in concentrated solutions, due to the formation of stable hydrogen bonded complex $\ce{[HF_2]-}$, the reaction is pushed in the forward direction making it a resonably strong acid (in fact strongest among corresponding concentrated solutions of all the hydrogen halides).So, you could generate a carbocation with that.However, as generally dilute solutions are used which are economically feasible, more stronger mineral acids in dilute solutions like $\ce{HCl, HBr}$ and $\ce{HI}$ are used.

EDIT:

As suggested by Oscar Lanzi in the comments, acids like $\ce{HCl, HBr}$ and $\ce{HI}$ are safer to handle when compared to $\ce{HF}$ as the reactions of $\ce{HF}$ are associated with highly negative enthalpy changes [highly exothermic]

Not just an economic advantage. HF is more dangerous to work with than HCl or HI, especially if you need a strong acid and thus would have to concentrate the HF. — Oscar Lanzi, Jul 03 '20 at 20:01
@OscarLanzi Thanks for adding value.I will update my answer to include this as well. — Chem-Learner, Jul 03 '20 at 20:18

Why does HF generate a carbocation with an alkene

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