Naming Conventions

Current Methods

The naming conventions for chemical compounds has evolved because of the need to have a systematic method for chemists to communicate with each other about the compounds that they synthesize. At the present time, two naming conventions coexist: the IUPAC system and the Common Name system. The latter naming method is still used for mostly historical reasons, since most people want to use simple names to refer to compounds that they work with on a regular basis. For example, water is a lot better than dihydrogen oxide for everyday use.

Graph Theory Application

The IUPAC system uses something akin to graph theory to specify the major topological features of molecules. In some cases, the two conventions are mixed. The following example illustrates this situation. The four molecules shown below are all dimethyl pyridine derivatives, but they have been given the common name lutidine. Although they all have the same chemical formula (C7H9N), clearly, these molecules are different, given the notion of graph isomorphism with respect to labeled graphs (in this case, actual molecules). The numbers in each of the molecule's' names correspond to the positions where the methyl (CH3) groups are attached relative to the nitrogen (N), which is assigned the number one position. As a result of their different (non-isomorphic) structures, these four molecules interact with the human sense of smell in quite different ways. The first structure, 2,6-lutidine, is judged to have the most horrid smell known to humankind. The other lutidines, while not pleasant, do not fall into this exclusive category of sensory extrema.

Variations of Lutidine

Copyright 2000 Rensselaer Polytechnic Institute. All Rights Reserved.