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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.

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1. An alternative thermochemical reference system Introduction Alkanes as reference substances Compounds containing O, N, S, F, Cl, Br and/or I 2. Hydrocarbons Alkanes Cycloalkanes Alkenes Monoolefines Cyclic mono-alkenes Di and polyolefines. Stabilization energy of butadiene Allenes Alkynes Aromatic hydrocarbons Stabilization energy of benzene Substituted benzene derivatives Polycyclic aromatic hydrocarbons 3. The oxygen derivatives of hydrocarbons Alcohols Vinyl alcohol Phenols Ethers Cyclic ethers Stabilization energy of furan Peroxides Aldehydes and ketones Acetals and ketals Carboxylic acids Carboxylic acid esters Carboxylic acid anhydrides Ketene and carbon dioxide 4. Organic compounds containing nitrogen Amines Azocycloalkanes Aromatic amines Carboxylic acid amides Hydrazine derivatives Nitriles Imines, oximes, hydroxylamines and azo compounds Heteroaromatic compounds Five member ring compounds. Stabilization energy of pyrrole Benzenoid heteroaromatic compounds Nitro compounds Organic nitrites and nitrates 5. Organosulfur compounds Thiols Organic sulfides Cyclic sulfides Stabilization energy of thiophene Thioaldehydes Carbothioic S-acids and esters Disulfides Sulfoxides, sulfones sulfites and sulfates 6. Organohalides Halogens Alkyl halides Alkenyl halides Aryl halides Halogen derivatives of carboxylic acids and esters Carboxylic acid halides Carbonyl halides 7. Radicals, cations, and anions Radicals Carbocations Carbanions Homolytic dissociation energies and relative enthalpies 8. Inorganic compounds Elements Hydrogen compounds of the elements Carbon sulfides and oxides Sulfuric acid, sulfur oxides and halides Nitrogen compounds 9. Components of the heats of reactions The relative enthalpies of the elements and their meaning Components of the heats of reactions Type 1 reactions Type 2 reactions Type 3 reactions Reactions preserving the starting number of molecules... Formation of alkyl halides by substitution reactions Formation of carboxylic acid esters and amides Formation of carboxylic acid anhydrides Reactions proceeding with reduction of the number of molecules Additions to unsaturated hydrocarbons Additions to functionalized derivatives of hydrocarbons Formation of acetals
Reactions proceeding with the increase of the number of molecules Formation of carboxylic acid chlorides The hydroperoxide rearrangement Cyclysation reactions Other reactions proceeding with the increase of the number of molecules

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