Please explain the popoff's rule

aldehydes can be converted to rcooh as more reactive but ketones get oxidised under drastic condition

by a rule popoff's

ketones are oxidised by conc hno3 acidified kmno4

during oxidation of ketone carbonyl bond and alpha carbon bond is broken and oxidised to respective carboxylics

fragment containing carbonyl bond forms major part (95%)

other forms minorbut the case is reversed if non carboyl part contains conjugations

Popoff's rule states that during oxidation of ketones, keto group always stays with the smaller alkyl group. For example,

CH3CH2COCH2CH2CH3 on oxidation with HNO3 gives two moles of propanoic acid, where in one mole of propanoic acid the cooh group comes from CH2 of propyl part of ketone.

CH3COCH2CH2CH3 on oxidation gives CH3COOH & CH3CH2COOH, here also the CH2 of propyl group is oxidised.

In both the examples the C=O remains with the smaller alkyl group,viz. CH3CH2 & CH3 respectively.

Mechanism is uncertain but probably proceeds with enol formation and depends on stability of enol