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The IUPAC International Chemical Identifier (InChI), developed by IUPAC and NIST, is a digital equivalent of the IUPAC name for any particular covalent compound. Chemical structures are expressed in terms of five layers of information – connectivity, tautomeric, isotopic, stereochemical, and electronic.
The InChI algorithm converts input structural information into the identifier in a three-step process: normalization (to remove redundant information), canonicalization (to generate a unique set of atom labels), and serialization (to give a string of characters).
Examples
| CH3CH2OH ethanol | InChI=1/C2H6O/c1-2-3/h3H,2H2,1H3 |
| InChI=1/C6H8O6/c7-1-2(8)5-3(9)4(10)6(11)12-5/h2,5,7-10H,1H2/t2-,5+/m0/s1 |
Layer types
There are six InChI layer types:
- Main layer
- Charge layer
- Stereochemical layer
- Isotopic layer
- Fixed-H layer
- Reconnected Layer
Sub-layers
Each layer can be split into sub-layers. For example, the main layer can be split up into three sub-layers:
- Chemical formula (no prefix)
- Atom connections (prefix: "c")
- Hydrogen atoms (prefix: "h")
Notation
Layers and sub-layers are both separated by the "/" delimiter. All layers and sub-layers (except for the chemical formula sub-layer of the main layer) start with a lower-case letter indicating the type of information held in that layer.
See also
External links
- IUPAC InChI site
- InChI.info - an unofficial InChI website featuring on-line converter from InChI to molecular drawings
- Unofficial InChI FAQ
- Generate InChI (interactive service at University of Cambridge, either interactive or WSDL)
- Search Google for molecules (generates InChI from interactive chemical and searches Google for any pages with embedded InChIs). Requires Javascript enabled on browser
- PubChem online molecule editor that supports SMILES/SMARTS and InChI
- MarvinSketch implementation to draw structures (or open other file formats) and output to InChI file format
Chemical nomenclature | Encodings | Chemical file formats | Cheminformatics
"International Chemical Identifier"