| 546 / | 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 consisting of one nitrogen and five carbons {24} | 
| 255 | DF | .~.~.~ Plural pyridine or partially hydrogenated pyridine rings {6} | 
| 262 |  | .~.~.~.~ Having -C(=X)-, wherein X is chalcogen, bonded directly to pyridine or partially hydrogenated pyridine ring {1} | 
| 263 | DF | .~.~.~.~.~> The -C(=X)- is part of a -C(=X)X- group, wherein the X's are the same or diverse chalcogens |