Hydroboration of an alkene
Boron and hydrogen add across the double bond, boron to the less hindered carbon, and the carbon–boron bond is then replaced by a hydroxyl with retention. The alcohol ends up on the opposite carbon from the one acid-catalysed hydration would give.
What it needs, and what it gives
- Reaction class
- Addition
- A borane, then hydrogen peroxide with hydroxide. Addition is syn.
- not stated
- Mechanism
- none written
- Boranes are pyrophoric; peroxide work-ups are exothermic.
These notes are flags, not a risk assessment. Read the primary source and your own institution's rules before working at the bench.
How it is thought to happen
The transformation is applied and tested, but no canonical pathway has been written for it yet. Rather than generate a plausible-looking set of arrows, the platform offers nothing here. What it does claim — which bonds change — is read from the transformation itself and does not depend on a mechanism.
Try it on your own structures
Enter your reactants in the Reaction Lab. If this transformation matches what you drew, it is applied and the outcome is shown next to the records that back it — with the count of documented reactions doing the same thing on substrates like yours, rather than a confidence score.
Other addition transformations
Conjugate addition
A stabilised carbanion adds to the far end of an enone rather than to its carbonyl.
Organometallic addition to a carbonyl
The carbon of the organometallic adds to the carbonyl carbon; the alcohol appears on work-up.
Alkene hydration
Water adds across a double bond. The hydrogen goes to the carbon that already has more of them and the hydroxyl to the other, so the more substituted alcohol is the one that forms.
Bromination of an alkene
Bromine adds across the double bond. The second bromide arrives on the opposite face from the first, so the two end up anti.
Dihydroxylation of an alkene
Two hydroxyls are delivered to the same face of the double bond, giving the cis diol.