the enol content of which is greater i)1,3,5 trihydroxy benzene ii)1,2,4 trihydroxy benzene. also explain why?

1 Answer
Jun 16, 2017

The enol content of ii) benzene-1,2,4-triol is greater.


Benzene-1,3,5-triol is a type of enol. It exists as two tautomers in equilibrium with each other.

Benzene-1,2,4-triol can also exist as tautomers.


However the two keto groups in the 1,2-position put two positively-charged carbonyl carbons adjacent to each other.

This destabilizes the system.

NMR studies show that the major tautomeric form is 2,5-dihydroxycyclohexa-2,4-dienone.


Thus, the 1,3,5-isomer has more of the keto form at equilibrium, and the 1,2,4-isomer has more of the enol form.