International Chemical Identifier

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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).

Contents 1 Examples 2 Layer types 3 Sub-layers 4 Notation 5 See also 6 External links

[edit] Examples

CH3CH2OH ethanol	InChI=1/C2H6O/c1-2-3/h3H,2H2,1H3
L-ascorbic acid	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

[edit] Layer types

There are six InChI layer types:

1. Main layer
2. Charge layer
3. Stereochemical layer
4. Isotopic layer
5. Fixed-H layer
6. Reconnected Layer

[edit] Sub-layers

Each layer can be split into sub-layers. For example, the main layer can be split up into three sub-layers:

1. Chemical formula (no prefix)
2. Atom connections (prefix: "c")
3. Hydrogen atoms (prefix: "h")

[edit] 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.

[edit] See also

• SMILES
• Molecule editor

[edit] 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
• Googling for InChIs a presentation to the W3C.
• Presentation on InChIs from the Googleplex
• InChIMatic Draw your molecule and Google will search for it