The IUPAC International Chemical Identifier (InChITM)) is a textual identifier for chemical substances, designed to provide a standard and human-readable way to encode molecular information and to facilitate the search for such information in databases and on the web. Initially developed by IUPAC and NIST during 2000–2005, the format and algorithms are non-proprietary. The continuing development of the standard has been supported since 2010 by the not-for-profit InChI Trust, of which IUPAC is a member.
InChIs can thus be seen as akin to a general and extremely formalized version of IUPAC names. They can express more information than the simpler SMILES notation and differ in that every structure has a unique InChI string, which is important in database applications. Information about the 3-dimensional coordinates of atoms is not represented in InChI; for this purpose a format such as PDB can be used.
The InChIKey, sometimes referred to as a hashed InChI, is a fixed length (25 character) condensed digital representation of the InChI that is not human-understandable. The InChIKey specification was released in September 2007 in order to facilitate web searches for chemical compounds, since these were problematic with the full-length InChI.
- IUPAC International Chemical Identifier