This brief introduces readers to an alternative thermochemical reference system that makes it
possible to use the heats of formation of organic compounds to deduce the energies that depend
entirely on their structures and which provides calculated values for most of the
characteristic structures appearing in organic molecules. These structure-dependent energies
are provided e.g. for selected compounds of normal and cyclic alkanes open chain and cyclic
olefins (including conjugated polyenes) alkynes aromatic hydrocarbons and their substituted
derivatives. The oxygen sulfur and nitrogen derivatives of the above-mentioned compounds are
also represented with calculated structure-dependent energies including alcohols ethers
aldehydes and ketones carboxylic acids thiols sulfides amines amides heterocyclic
compounds and others. Most organic reactions can be interpreted as the disappearance of certain
structures and formation of others. If the structure-dependent energies are known it can be
shown how the disappearing and the newly formed structures contribute to the heat of reactions
and to the driving forces. As experienced by the author who pioneered the concept structure
dependent energies can help teachers to make organic chemistry more accessible for their
students. Accordingly the brief offers a valuable resource for all those who teach organic
chemistry at universities and for those who are learning it.
