# Are homodesmotic reactions exothermic reactions?

##### 1 Answer
Dec 27, 2014

Homodesmotic reactions can be either exothermic or endothermic.

They may be hypothetical reactions, that is, ones that could never occur.

They are used in thermodynamic calculations, so they can be written in a forward or reverse direction.

Depending on the direction, they can be either exothermic or endothermic.

An example of a homodesmotic reaction involving cyclopropane is

cyclo-(CH₂)₃ + 3CH₃-CH₃ → 3CH₃CH₂CH₃

ΔH° = -110.9 kJ/mol

If we wrote the equation in the reverse direction, the process would be endothermic.