Question

How can I assess strain energy of cyclopropane and aromatic stabilization of benzene with homodesmotic reactions?

Answer 1

You can find out how to assess the strain energy of cyclopropane here.

To assess the aromatic stabilization of benzene, you determine the energy change for the reaction

`"C"_6"H"_6 + "3CH"_2"=CH"_2 → "3CH"_2"=CH–CH=CH"_2`

All bonds are `sp^2` C-H σ bonds, C-C σ bonds, and C-C π bonds.

Each side of the equation has

• 18 `sp^2` σ C-H bonds
• 3 `sp^2` σ C-C bonds
• 6 `sp^2` C-C π bonds

Since all bond types are matched, the value of `ΔH` represents the aromatic stabilization of benzene.