Why does the potassium manganate used to oxidise alkenes have to be acidified?

Question

Alkenes which are oxidised to diols are done so through potassium manganate acidified? why acidified?

c2h4 + [O] --> ch2ohch2oh

mno4- H+

Answer 1

KMnO4 has two different reduction products, depending on pH. This also affects oxidation potential.

In neutral or alkaline solution, MnO2 is produced:

MnO4(-) + 4H2O + 3 e(-) -> MnO2 + 4 OH(-)

In acidic solution, Mn(2+) is produced:

MnO4(-) + 8 H(+) + 5 e(-) -> Mn(2+) + 4 H2O

The H+ of the acid might act as an electrophile in the reaction with the alkene, too.