The /h hydrogens layerStep 8 of 17 of the InChI walkthrough. The /h layer puts the hydrogens back. Atoms carrying the same number of hydrogens are collected into one run, the runs are ordered by hydrogen count, and consecutive atom numbers collapse into a range. Caffeine’s 4H,1-3H3 says atom 4 carries one hydrogen and atoms 1 to 3 carry three each.It opens on CN1C=NC2=C1C(=O)N(C)C(=O)N2C, 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

Download — take the engine away

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