Syn Dihydroxylation of Alkenes Question #alkenes

Added: 2026-06-04

[00:00:00]Five. What is the product of the following reaction? So we are looking at these reaction conditions and we have to memorize that these conditions produce sin dihydroxilation. So this is one of those flashc card reactions. We need to be able to look at those reaction conditions and know that this means sin dihydroxilation.

[00:00:21]So what does that mean? That's the part that we have to memorize. We have to memorize that those conditions mean sin dihydroxilation and the tip off is the osbium troxide. If we've memorized that then we just have to know what those words mean. So dihydroxilation means that we're adding hydroxal groups. We're adding two hydroxal groups, one to each carbon participating in the double bond.

[00:00:45]And sin means we're adding them to the same side of the molecule. So we're going to add a hydroxil there. We're going to add a hydroxil there. and they're going to be added to the same side of the molecule. So, which ones can we get rid of? A does not work because we only added one hydroxil. We're doing a dihydroxilation.

[00:01:03]B doesn't work because we lost a methyl group. We don't want to lose any carbons. That doesn't make any sense.

[00:01:08]So, C and D both look like the correct structure. But what about the stereochemistry? If the hydroxils were added to the same side of the molecule, they have to be cyst to one another in the product. So D is the one that works because these are cyst to one another.

[00:01:25]So they were added sin. This does not work. We don't want the hydroxils to be trans to one another because then they would have been added anti. They would have been added on opposite sides of the molecule. But the reason that osmium troxide adds sin is because you have a central osmium atom and the two oxygens being added are coming from the same compound. So they must add to the same side of the molecule. So they will be cis on the product. So that will be option D.