US PATENT SUBCLASS 549 / 231
.~.~.~ Cyclic anhydrides (i.e., -C(=X)OC(=X)-, wherein the X's are the same or diverse chalcogens, is part of the hetero ring)

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549 /   HD   ORGANIC COMPOUNDS -- PART OF THE CLASS 532-570 SERIES

*  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}
200  DF  .~.~ Oxygen containing hetero ring (e.g., dioxirane, etc.) {16}
231.~.~.~ Cyclic anhydrides (i.e., -C(=X)OC(=X)-, wherein the X's are the same or diverse chalcogens, is part of the hetero ring) {2}
232  DF  .~.~.~.~> The cyclic anhydride has at least six members and is a cyclo in a polycyclo ring system
233  DF  .~.~.~.~> The cyclic anhydride is five-membered (e.g., succinic anhydride, etc.) {7}

DEFINITION

Classification: 549/231

(under subclass 200) Compounds wherein the hetero ring is a cyclic anhydride; i.e., --O- is part of the ring, X's are the same or different chalcogens (i.e., oxygen, sulfur, selenium or tellurium).

(1) Note. Examples of compounds provided for herein are: [figure] [figure]