Question

How do you make primary alcohol from an alkene?

Answer 1

Hydroboration are the typical means to make a primary alcohol from an olefin.

Explanation:

When an olefin is treated with aqueous acid, `H^+` adds as an electrophile. And so the most stable resultant carbocation is the one with most substitution. Propylene would give predominately `"2-propanol"` on acidic hydration.

On the other hand, when say `"2-methylpropene"` is treated with borane in THF, the hydrogen adds as an hydride:

`H_2C=C(CH_3)CH_3 +B""^2H_3 rarr (""^2H_2BCH_2C-C""^2H(CH_3)CH_3)` (I labelled the borane so you could see how the hydrogens add. The `B-H` bond adds across the olefin in a concerted mechanism.)

Here, the electron-deficient boron centre is the electrophile.

Oxidative work up gives the primary alcohol `HO-CH_2C-CH(CH_3)CH_3` and an inorganic borate.