Question

Hydroxylation of Maleic acid by KMnO4 gives

a) meso-tartaric acid b) (dl)-butan-2,3-diol c) (dl) -tartaric acid d) (+)tartaric acid​

Answer 1

Answer:

Hydroxylation of a double bond by alk. KMnO4 (or OSO4) is predominantly cis and proceeds via a cyclic intermediate (ester) which on hydrolysis gives the cis diol. Hence for e.g. maleic acid gives mesotartaric acid and fumaric acid (molecule is flat) gives (+ ) tartaric acid (pair of enantiomers).