why does b.v. oxidation of 1,2 diketones give anhydrides????

THIS ANSWER CAN ONLY BE EXPLAINED BY MECHANISM. I CAN'T TYPE THE MECH. BUT STILL GIVING U SOME SUGGESTION.

START THE NORMAL MECH. PROCEDURE OF B.V REACTION i.e. PROTONATE ONE CARBONYL GR. THEN ATTACK THAT BY NUCLEOPHILIC CENTRE OF PER-ACID.PROCEED UPTO REMOVAL OF -HCOOH.*NOW DO CHARGE SEPARATIONOF THE OTHER CARBONYL GR.--FORM THE EPOXY COMPOUND. NOW BREAK C-C BOND DUE TO FORMATION OF -CO FROM -COH. i THINK NOW U CAN DO THE REST.

*FROM HERE ONWARDS THIS MECH. CHANGES FROM THOSE ROUTINE ONE.

THIS IS A GOOD MECH. INTERESTING ONE.