In general compounds are classified and named by consideration of: a) the number and types of atoms that are present, b) the bond types in the molecule, and c) the geometry of the molecule.
Formulae
Prior to setting out the rules for naming compounds it is pertinent to review some aspects of formulae. The molecular formula of a compound gives no explicit information about the structure of the compound. The formula C2H6O makes no mention as to how the various atoms are arranged, indeed two different compounds share this formula but have different structures and vastly different properties.
As indicated previously, compounds are classified in terms of their structure and are named accordingly. The simplest classification is that of the hydrocarbons, compounds of carbon and hydrogen. Hydrocarbons are further identified as being aliphatic or aromatic (nothing to do with smell).
The aliphatics may be alkanes, alkenes or alkynes; aromatic hydrocarbons contain one or more benzene rings.
It is important that students get a good grasp of the convention used in naming the simplest class, the alkanes, as the naming of other classes is an extension of alkane nomenclature.
• contain only C, H
• are saturated, i.e. contain only single bonds
• straight chain (normal) alkanes are named according to the number of C atoms present.
• normal alkanes form a series, a homologous series of formula CnH2n+2 where n is an integer.