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

Question

The enthalpy of hydrogenation of cyclohexene is -119.5 kJ mol -1. If resonance energy of benzene is -150.4 kJ mol -1, its enthalpy of hydrogenation would be (A) -208.1 kJ mol -1 (B) -269.9 kJ mol -1 (C) -358.5 kJ mol -1 (D) -508.9 kJ mol -1

Tardigrade Admin · Accepted Answer

The enthalpy of hydrogenation of cyclohexene (having one double bond) is

- 119.5 k J m o l^{- 1}

.
Hence, theoretically enthalpy of hydrogenation of Kekule's structure of benzene should be

3 \times (- 119.5) k J m o l^{- 1}

.
Since the resonance energy of benzene is

- 150.4 k J m o l^{- 1}

, the actual enthalpy of hydrogenation of benzene will be,

= [3 \times (- 119.5)] - (- 150.4)

= - 208.1 k J m o l^{- 1}

.

Q. The enthalpy of hydrogenation of cyclohexene is $- 119.5 k J m o l^{- 1}$ . If resonance energy of benzene is $- 150.4 k J m o l^{- 1}$ , its enthalpy of hydrogenation would be

$- 208.1 k J m o l^{- 1}$

$- 269.9 k J m o l^{- 1}$

$- 358.5 k J m o l^{- 1}$

$- 508.9 k J m o l^{- 1}$

Q. The enthalpy of hydrogenation of cyclohexene is −119.5kJmol−1. If resonance energy of benzene is −150.4kJmol−1, its enthalpy of hydrogenation would be

−208.1kJmol−1

−269.9kJmol−1

−358.5kJmol−1

−508.9kJmol−1

Q. The enthalpy of hydrogenation of cyclohexene is $- 119.5 k J m o l^{- 1}$ . If resonance energy of benzene is $- 150.4 k J m o l^{- 1}$ , its enthalpy of hydrogenation would be

$- 208.1 k J m o l^{- 1}$

$- 269.9 k J m o l^{- 1}$

$- 358.5 k J m o l^{- 1}$

$- 508.9 k J m o l^{- 1}$