# Are homodesmotic reactions isodesmic reactions?

Dec 26, 2014

Yes, homodesmotic reactions are a subset of isodesmic reactions.

An isodesmic reaction is a reaction that has the same number and type of bonds in the reactants and in the products.

An example of an isodesmic reaction is

Homodesmotic reactions are a subclass of isodesmic reactions.

Here, the reactants and products are even more similar. They must contain equal numbers of

• atoms in the same state of hybridization
• groups containing the same number of H atoms.

An example of a homodesmotic reaction is

The reactants and products contain equal numbers of bonds between carbons in the same state of hybridization and hydrogens bound to identical atom types.

${C}_{s {p}^{3}} \text{-} {O}_{s {p}^{3}}$ = 1

${C}_{s {p}^{3}} \text{-} {C}_{s {p}^{2}}$ = 1

${C}_{s {p}^{2}} \text{-} {O}_{s {p}^{3}}$ = 1

${C}_{s {p}^{2}} \text{-} {C}_{s {p}^{2}}$ = 7

${C}_{s {p}^{2}} \text{=} {C}_{s {p}^{2}}$ = 6

${C}_{s {p}^{3}} {H}_{3}$ = 2

${C}_{s {p}^{2}} {H}_{2}$ = 2

${C}_{s {p}^{2}} H$ = 9