In my grade 12 Chemistry class, we’ve been learning several reactions that organic compounds go through. Most of them make sense, but our teacher doesn’t know the mechanism for hydroxylation reactions of alkenes, and for the life of me, I can’t figure it out. Here’s a sample hydroxylation reaction(note: the reaction only takes place in the presence of OH- ions)
C2H4 + KMnO4 ----> C2H4(OH)2
Our teacher said that she looked in both a first-year university and a second-year university textbook, and both were written this way without explanation. Anyone know how this works? And can you explain it to a high school student in a way that I’ll understand?
Here’s a little more detail from Morrison and Boyd, Organic Chemistry, 3rd ed. (cause my schooling was a long time ago.)
3CH[sub]2[/sub]=CH[sub]2[/sub] + 2KMnO[sub]4[/sub] + 4H[sub]2[/sub]O ----> 3 CH[sub]2/subCH[sub]2/sub + 2 MnO[sub]2[/sub] + 2 KOH
A proper chemist should be along shortly with some useful information.
As is often said, a picture is worth a thousand words. Note that the “O” of each resulting “OH” comes from the manganate (or, in the example from the link, the osmate) compound, while the “H” comes from the hydroxide compound.
osmium tetroxide and permanganate is probably a concerted reaction as shown in the diagram. One bit of evidence is that both oxygens are added on the same side of the double bond - i.e probably at the same time. Thus usually implies a cyclic transition state as shown. They have also shown in the case of osmium that the oxygens come from the tetroxide, rather than from the solvent or air.
You can actually test whether the reaction is cyclical by checking the chirality of the end product (substituting one of the Hs for, say, a halogen). Some reactions occur trans, cyclic reactions occur cis. You find that with these reagents, the reaction is cis… more evidence for cyclic.
Somebody help me - I knew at least the outline of the answer off the top of my head. Before I even read the OP. Sob