The enthalpy of hydrogenation of cyclohexene is `-119.5kJ mol^(-1)`. If resonance energy of benzene is `-150.4kJ mol^(-1)`, its enthalpy of hydrogenation would be `:`

Options

A. `- 269.9 kJ mol^(-1)`
B. `- 358.5 kJ mol^(-1)`
C. `-508.9 kJ mol^(-1)`
D. `- 208.1kJ mol^(-1)`

Answer

D

Explanation

Breaking of one C= C bond and forming C-H bond require 119.5kJ/mole of energy

Resonance energy = -Actual enthalpy + observed enthalpy `rArr -150.4`
= - Acutal enthalpy `+(-3 xx 119.5)`
Actual enthalpy = +150.4 - 358.5= -208.1 kJ/mole