US PATENT SUBCLASS 549 / 256
.~.~.~.~.~ Preparing by oxidation

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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  DF  .~.~.~ 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}
233  DF  .~.~.~.~ The cyclic anhydride is five-membered (e.g., succinic anhydride, etc.) {7}
256.~.~.~.~.~ Preparing by oxidation {2}
257  DF  .~.~.~.~.~.~> Of benzene or hydrocarbyl substituted benzene
258  DF  .~.~.~.~.~.~> Of acyclic or alicyclic hydrocarbon {1}

DEFINITION

Classification: 549/256

(under subclass 233) Processes wherein a five-membered cyclic anhydride is prepared by an oxidation reaction.

(1) Note. Among the processes provided for herein are: oxidation of crotonaldehyde to meleic anhydride, oxidation of furfural to maleic anhydride, and oxidation of mesityl oxide to citraconic anhydride.