Numbering 2 — refine on the neighboursStep 5 of 17 of the InChI walkthrough. Two atoms with the same invariants can still sit in different surroundings. Refinement separates them: re-rank every atom by its own rank followed by the sorted ranks of its neighbours, and repeat until nothing splits any further. In 2-methylbutane the three methyls start tied; one round separates the one on the ethyl arm from the two on the isopropyl end.It opens on CC(C)CC, drawn live, so the layer under discussion changes as you change the structure.Convert a structure to its InChI and InChIKey and back, convert a whole CSV, XLSX or SDF file, learn how the identifier is derived, and practise writing its layers. The InChI engine is WebAssembly running in your browser, so the tool needs JavaScript — and nothing you open ever leaves your machine.

Convert — a structure in, an InChI out

Batch — a whole CSV, XLSX or SDF file

Tutorial — how an InChI is derived

Exercises — write the layers yourself

Cheatsheet — every layer in a table

Tests — the IUPAC regression corpora

Download — take the engine away

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