A new definition of functional groups and a general procedure for their identification in organic structures

Functional groups (FGs) have always been used to describe structures and reactivities of organic molecules, therefore their univocal identification is important. Current approaches are often subject to limits and errors, using descriptions that are either too approximated or too rigid. A new definition, and the corresponding search procedure, based on the calculation of a molecular descriptor is introduced and applied to some molecules of different complexity. Results show a consistent set of FGs for each structure. They are divided into two classes - first level FGs and second level FGs - that describe interactions either among atoms (first level) or among groups of atoms (second level).