MOLGEN+, a generator of connectivity isomers and stereoisomers for molecular structure elucidation

The structure generator MOLGEN produces all the molecular graphs that correspond to a given chemical formula and (optionally) prescribed and forbidden substructures as well as further optional conditions like intervals for possible ring sizes, hybridization of carbon atoms (not completely implemented), etc. It does this in a fast and redundancy free way, which seems, to our knowledge, to be more efficient than all the other molecular generators known [see R. Grund, A. Kerber and R. Laue, MATCH, 27 (1992) 87, for introductions to various other generators]. Afterwards these molecular graphs can be displayed on the computer screen, 3D-placements of them (using an energy model) can be computed, and the stereoisomers can be calculated and visualized basing on this placement. Therefore, this generator serves very well as the mathematical core of computer packages for molecular structure elucidation. Moreover, it can easily be used for demonstrations in chemical education. MOLGEN developed from MOLGRAPH [introduced in A. Kerber, R. Laue and D. Moser, Anal. Chim. Acta, 235 (1990) 221]. In contrast to MOLGRAPH it has a much wider range of application since it does not need a catalog of precomputed cyclic substructures.