The order of stability of the following tautomeric compounds is
(i). `CH_(2)=overset(OH)overset(|)(CH)-CH_(2)-overset(O)overset(||)(C)-CH_(3)hArr`
(ii). `CH_(3)-overset(O)overset(||)(C)-CH_(2)-overset(O)overset(||)(C)-CH_(3)hArr`
(iii). `CH_(3)-overset(OH)overset(|)(C)=CH-overset(O)overset(||)(C)-CH_(3)`

Options

A. `III gt II gt I`
B. `II gt I gt III`
C. `II gt III gtI`
D. `I gt II gt III`

Answer

A

Explanation

Enolic form predoninates in compounds containing two carbonyl groups separated by a `-CH_(2)` group. This is due to following two factors.
(i) Presence of conjugation which increases stability.
(ii) Formation of intramolecular hydrogen bond between enolic hydroxyl group and second carbonyl group which leads to stablisation of the molecule. Hence the correct answer is `III gt II gt I`.