I am interested in knowing how diols are produced when you introduce a reagent like potassium permanganate to an alkene. What is the mechanism for these reactions? The hydroxyl substituents happens to be at the 1,2 position each time.
That's a particular case of syn-dihydroxylation, also known as Wagner reaction. "Syn-dihydroxylation" means that a double bond is cleaved into a single bond and two OH groups are attached to the carbon atoms that were involved into a double bond from the same side. Anti-addition is not possible as permanganate anion can't be attached to the double bond from different sides of the bond due to steric reasons.
There is a Khan Academy video that describes the mechanism of this particular addition, but that video is all about different cases of syn-addition.
In brief, the mechanism can be also drawn as following: