with only hydrogen atoms or radicals containing only hydrogen and carbon atoms directly attached to other ring carbon atoms

Full Title

Heterocyclic compounds containing five-membered rings not condensed with other rings, with one nitrogen atom as the only ring hetero atom > with only hydrogen or carbon atoms directly attached to the ring nitrogen atom > having one double bond between ring members or between a ring member and a non-ring member > with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms > Oxygen or sulfur atoms > 2-Pyrrolidones > with only hydrogen atoms or radicals containing only hydrogen and carbon atoms directly attached to other ring carbon atoms