Part I. FUNDAMENTALS OF STRUCTURE AND REACTIVITY OF ORGANIC COMPOUNDS

Chapter 1

CLASSIFICATION AND NOMENCLATURE OF ORGANIC COMPOUNDS

The problems of classification and nomenclature are especially relevant to organic chemistry, as its objects of study are millions of compounds. The nomenclature must be systematic and international, so that professionals from all over the world could unambiguously represent the structure of any compound, and, vice versa, write the structure by the name. In addition, the nomenclature must be suitable for computer processing.

1.1. Classification

The classification of organic compounds is based on two capital features:

• a structure of molecular carbon skeleton;

• the presence of functional groups in a molecule.

Regarding the structure of carbon skeleton organic compounds are subdivided into the following groups.

Acyclic (aliphatic) compounds. They may have unbranched or branched carbon chains.

Carbocyclic compounds. Their carbon chain forms a cycle (ring). When describing cyclic structures, it is more convenient to use so-called skeletal formulas. In such formulas the end of a skeletal line and its every angle imply a carbon atom with enough hydrogens (taking into account the tetravalency of the carbon atom). Extracyclic groups are often written in full.

Heterocyclic compounds. They contain a cyclic skeleton, which in addition to carbon atoms contains at least one different atom (heteroatom) - most often nitrogen, oxygen, or sulfur.

Most organic molecules contain functional groups. That is a part of the molecule that determines its chemical properties and belonging to a certain class (Table 1.1). Such groups necessarily contain a heteroatom. A compressed notation in a line is commonly used to refer to functional groups with multiple bonds: -CO- or -C(O)-, -COOH, -NO₂, -SO₃H, as is shown in general formulas of the classes