Explanatory notes
… whose molecules contain, in addition to atoms of hydrogen, oxygen or nitrogen, those of metals or other non-metals … two hetero-atoms : (a) One oxygen, one nitrogen : Oxazole and isoxazole groups (heading 29.34)* . (b) One … two hetero-atoms : (a) One oxygen, one nitrogen : Oxazine group (heading 29.34)* . (b) One sulphur, one …
