The /q and /p charge layersStep 10 of 17 of the InChI walkthrough. Charge is split in two. The /p layer counts protons added to or removed from the neutral skeleton, so an acid and its conjugate base differ only there. Whatever charge is left after that goes in /q. Acetate is /p-1; a quaternary ammonium, which no proton count can neutralise, gets /q+1 instead.It opens on CC(=O)[O-], 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

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Tutorial — how an InChI is derived

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Cheatsheet — every layer in a table

Tests — the IUPAC regression corpora

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