More About the InChI Standard

More about the InChI Standard

• Digital technologies introduce new challenges for the communication of chemical information

• Databases used [often proprietary] registry lookup identifiers that made correlation of chemical information difficult

•. Non-canonical line notations resulted in redundant structural representations that complicated information processing.

• Chemical nomenclature needed to be extended to the digital representation of chemical structural information

Digital Representation of Chemicals: Hack-a-Mol

A structure such as caffeine can be drawn in 2D, compared with its 3D structure, and also view its structured data in a variety of formats. It can also be entered through a variety of chemical identifiers: a chemical name, a SMILES string, or a Chemical Abstracts Register Number, for instance.

MILESN1(C)C(=O)/C/2=C/3\N(C)C1=O.N\2(C)/C=N\3   at ChEMBL

_X_ MOL/SDF  ___ XYZ  ___ PDB  ___ CIF 


Extensions to InChI:

InChI Trust Working Group Initiatives

RInChI – Reaction InChI2

MInChI – Mixtures InChI3

Isotopologues & Isotopomers4

•extend the isotopic layer to include mixtures ofisotopologues and isotopomers

Tautomerizer – Introduction

Introduction | Form | Individual Rule Pages | Rules Sources | Help

Experimental service that allows you to test a set of tautomeric transforms with your own molecules. The predefined set of transforms comprises both the current 20 standard rules used by the chemoinformatics toolkit CACTVS and 45+ additional rules compiled in the context of the IUPAC project “Redesign of the Handling of Tautomerism in InChI V2”8.

Web tool created by the NCI CADD Group in the context of the InChI project “Redesign of the Handling of Tautomerism in InChI V2”. https://upac.ora/projects/project-details/?proiect+n=2012-023-2-8008

NinChi – InChI for Nanomaterials6

Layer 1 (version); Layer 2 (composition, morphology, size, crystal phase, chirality); Layer 3 – organisation of the constituents

VinChi – Variable / Markush InChI7


[1] Hanson, Bob, Hack-a-Mol, this poster. 

[2] Grethe, G., Blanke, H., Kraut, H. & Goodman, J.M., International Chemical Identifier for Reactions (RInChI), J. Cheminformatics 2018, 10, 22.  DOI:

[3] Clark, A.M., McEwen, L.R., Gedeck, P. et al. J Cheminformatics (2019) 11: 33.

[4] Tautomerizer – Introduction:

[5] Missing?

[6] Lynch, et. a.l., Can an InChI for Nano Address the Need for a Simplified Representation of Complex Nanomaterials across Experimental and Nanoinformatics Studies.

[7] Goodman, J.M.

[8] Redesign Tautomerism for InChI:


This work is supported by IUPAC (project 2018-012-3-024) and the InChI Trust. 

Content including text and graphics on this page originally appeared on a poster presented by:

Robert E. Belford1*Jordi Cuadros2*, Ehren C. Bucholtz3, Andrew P. Cornell1 & Tanya Gupta4

1University of Arkansas Little Rock, 2IQS Univ. Ramon Llull, 3University of Health Sciences and Pharamcy, 4South Dakota State University 

* (author for correspondence)

LINK to original poster (coming soon)