Project Details Enhanced recognition and encoding of stereoconfiguration by InChI tools

Project No.:
Start Date:
09 September 2019
End Date:


InChI tools are widely used as substance identifiers in various sources of chemical information. However, the current support of stereochemical information is limited to tetrahedral, double bond and short allene stereoisomerism. Among the unsupported stereo types are atropisomers and some special cases including centers with more than four ligands. An additional significant problem is an incomplete recognition of configurations for very common Haworth and chair representations of carbohydrates. The absence of support for MOLFile V3000 enhanced stereo used to represent relative and racemic configurations is another significant limitation.
Updated procedures will allow InChI to support additional stereochemical cases and avoid mistakes in designation of stereoisomers.

> Access InChI SubCommittee


InChI and InChIKey already are very useful for identification and search of substances in various sources of chemical information. While InChI tools resolve most aspects of constitutional isomerism, especially for organic substances, some types of stereoisomerism and representations of stereoconfiguration are not recognized. The most significant examples include atropisomerism and very common representation of carbohydrates in Haworth and chair forms. Unsupported stereoisomerism types results in the inability to distinguish specific isomers and the incorrect treatment of some representations results in incomplete or even wrong InChI identifiers.

Another distinct problem is the unsupported MOLFile V3000 enhanced stereo information that is currently used to represent mixtures of stereoisomers for industrial chemicals. Such structures are currently incorrectly interpreted by InChI tools as representing single stereoisomers.

Other problems that the project intends to address include nontetrahedral stereoconfigurations often encountered in coordination compounds but existing for organic compounds as well and unrecognized configurations for several specific cases including pyramidal arrangements and cumulenes with more than three cumulated bonds. The development of the principles for recognition and encoding of configurations for coordination structures will take into account the results of InChI for organometallics project 2009-040-2-800.

See FAQs on


Project announcement published in Chem Int Jan 2020, p. 30

Page last updated 12 Feb 2020