# How does the mechanism for hydroborations with BH_3 in alkene happen?

Dec 23, 2014

The hydroboration of alkenes is a single-step concerted mechanism.

The π electrons act as the nucleophile with the electrophilic B atom, and the H is transferred to the C with syn stereochemistry.

Note that B is more electronegative than H, so B is the positive end of the B-H bond.

Like H⁺ in a Markovnikov addition, the B atom adds to the C with more H atoms.

The boron adduct can then be oxidized to an alcohol.

Here's a video on the hydroboration of alkenes.