InChI: open-source chemical structure representation algorithm

Tautomer Identification and Tautomer Structure Generation Based on the InChI Code

Tautomer Identification and Tautomer Structure Generation Based on the InChI Code
Authored by:
Torsten Thalheim
Armin Vollmer
Ralf-Uwe Ebert
Ralph Kühne
Gerrit Schüürmann


An algorithm is introduced that enables a fast generation of all possible prototropic tautomers resulting from the mobile H atoms and associated heteroatoms as defined in the InChI code. The InChI-derived set of possible tautomers comprises (1,3)-shifts for open-chain molecules and (1,n)-shifts (with n being an odd number >3) for ring systems. In addition, our algorithm includes also, as extension to the InChI scope, those larger (1,n)-shifts that can be constructed from joining separate but conjugated InChI sequences of tautomer-active heteroatoms. The developed algorithm is described in detail, with all major steps illustrated through explicit examples. Application to ∼72 500 organic compounds taken from EINECS (European Inventory of Existing Commercial Chemical Substances) shows that around 11% of the substances occur in different heteroatom−prototropic tautomeric forms. Additional QSAR (quantitative structure−activity relationship) predictions of their soil sorption coefficient and water solubility reveal variations across tautomers up to more than two and 4 orders of magnitude, respectively. For a small subset of nine compounds, analysis of quantum chemically predicted tautomer energies supports the view that among all tautomers of a given compound, those restricted to H atom exchanges between heteroatoms usually include the thermodynamically most stable structures.

Content Type Non OER
Uploaded By Andrew Cornell
License Copyright © 2019 American Chemical Society
Content Status publish
Number of Comments No Comments
Date Published June 29, 2010
Content Tags Algorithm, Audience, Content type, Curricular Material, Document, English, File Type, Graduate, HTML, InChI Algorithm and Description, Language, Organic Chemistry, PDF, Publication, Researcher, Software