Chapter 14, Problem 14.9P

Interpretation Introduction

(a)

Interpretation:

Based on the heat of hydrogenation, aromaticity of $\text{cyclopenta-1, 3-diene}$ is to be determined.

Concept introduction:

The heat of hydrogenation depends on how many moles of ${\text{H}}_{\text{2}}$ are required to completely hydrogenate the compound. The number of ${\text{H}}_{\text{2}}$ moles required is equal to the number of double bonds present in the compound. This number of ${\text{H}}_{\text{2}}$ moles can hydrogenate an equal number of moles of cyclohexene, releasing $\text{120 kJ/mol}$.

If the difference between the calculated heat of hydrogenation and the measured heat of hydrogenation of a compound is comparable to the stabilization in benzene, about $\text{150 kJ/mol}$, then the compound is aromatic. If it is much less than this, then the compound is nonaromatic.

Interpretation Introduction

(b)

Interpretation:

Based on the heat of hydrogenation, aromaticity of Naphthalene is to be determined.

Concept introduction:

The heat of hydrogenation depends on how many moles of ${\text{H}}_{\text{2}}$ are required to completely hydrogenate the compound. The number of ${\text{H}}_{\text{2}}$ moles required is equal to the number of double bonds present in the compound. This number of ${\text{H}}_{\text{2}}$ moles can hydrogenate an equal number of moles of cyclohexene, releasing $\text{120 kJ/mol}$.

If the difference between the calculated heat of hydrogenation and the measured heat of hydrogenation of a compound is comparable to the stabilization in benzene, about $\text{150 kJ/mol}$, then the compound is aromatic. If it is much less than this, then the compound is nonaromatic.