Hydroboration of 3-methyl-2-hexene. #hydroboration #antimarkovnikov #orgochem #alkene #borane

Added: 2026-05-17

[00:00:00]So, what we have here is a hydroboration reaction mechanism. Your starting reactant is a simple unsymmetrical alkene. Your reagent is BH3 simple borane. This is an anti-Markovnikov regioselective reaction in that the boron will attach to the least substituted side of your alkene. Your hydrogen will attach to the more substituted side of your alkene. It is a syn addition because the B and the H will attach the same face of the alkene at the same time. Another thing to note is that this is a concerted reaction mechanism. All bonds break and form at the same time.

[00:00:37]And your transition state does not have a carbocation. What you have instead is a four-centered high energy transition state that looks like this.

[00:00:54]So, here you have your transition state where the boron is bearing a partial positive charge. The hydrogen is bearing a partial negative charge because I needed to remember that hydrogen is more electronegative than boron. And you end up with your hydroboration product that looks like that.