| 548 / | HD | ORGANIC COMPOUNDS -- PART OF THE CLASS 532-570 SERIES |
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| * | DD | ORGANIC COMPOUNDS (Class 532, Subclass 1) {1} |
| * | DD | .~ HETEROCYCLIC CARBON COMPOUNDS CONTAINING A HETERO RING HAVING CHALCOGEN (I.E., OXYGEN, SULFUR, SELENIUM, OR TELLURIUM) OR NITROGEN AS THE ONLY RING HETERO ATOMS (Class 540, subclass 1) {4} |
| 100 | DF | .~.~ Hetero ring is five-membered having two or more ring hetero atoms of which at least one is nitrogen (e.g., selenazoles, etc.) {18} |
| 250 | DF | .~.~.~ Tetrazoles (including hydrogenated) {3} |
| 252 | DF | .~.~.~.~ Chalcogen attached indirectly to the tetrazole ring by nonionic bonding {1} |
| 253 |  | .~.~.~.~.~ The chalcogen, X, is in a -C(=X)- group |