I am currently testing a piece of software that generates the InChI for a given structure. I also want to test error situations as end users will also deliver the mol files that will be used as input for the software.
I have found this description about what the current version of InChI cannot represent
InChI currently does not support the representation of:
- Polymers
- Complex organometallics
- Markush structures
- Mixtures
- Conformers
- Excited state and spin isomers
- Non-local stereochemistry/chirality
- Topological isomers
- Cluster molecules
- Polymorphs
- Unspecific isotopic enrichment
- Reactions
Also, InChI is not suitable for very large compounds; technically, InChI input may not contain more than 1023 atoms.
Please note that there are IUPAC InChI subcommittee working groups currently addressing some of these matters. Details of these efforts can be found at: http://iupac.org/web/ins/802
Unfortunately I am lacking the chemical background to generate a suitable structure as molfile that meets the described features to produce an error as an InChI cannot be generated for it.