Hi Adelene, You can't match an atom that doesn't exist as a node in the molecular graph, so if you really want to match a hydrogen, you'll have to add explicit hydrogens to your molecule:
molh = Chem.AddHs(mol) molh.HasSubstructMatch(q1) > True However, if all you want to know is whether the oxygen is next to a hydrogen, you can make the hydrogen count a property of the oxygen atom by using SMARTS: q3s = 'CCOCCOCCC[OH]' q3 = Chem.MolFromSmarts(q3s) mol.HasSubstructMatch(q3) > True Hope this helps, Ivan
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