| 549 / | 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) {2} |
| 1 | DF | .~.~ Sulfur containing hetero ring (e.g., thiiranes, etc.) {9} |
| 13 |  | .~.~.~ The hetero ring is six-membered {3} |
| 14 | DF | .~.~.~.~> Plural ring hetero atoms in the hetero ring {3} |
| 23 | DF | .~.~.~.~> Polycyclo ring system having the hetero ring as one of the cyclos {2} |
| 28 | DF | .~.~.~.~> Chalcogen or nitrogen attached directly to the hetero ring by nonionic bonding |