| 544 / | 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) {1} |
| 1 | DF | .~.~ Hetero ring is six-membered having two or more ring hetero atoms of which at least one is nitrogen (e.g., selenazines, etc.) {6} |
| 224 | DF | .~.~.~ The six-membered hetero ring consists of two nitrogens and four carbons (e.g., 1,2-diazines, etc.) {9} |
| 242 | DF | .~.~.~.~ 1,3-diazines {10} |
| 322 | DF | .~.~.~.~.~ Nitrogen attached directly to diazine ring by nonionic bonding {3} |
| 330 | DF | .~.~.~.~.~.~ At 2-position {2} |
| 331 |  | .~.~.~.~.~.~.~ Additional hetero ring which is unsaturated |