Citraconate 2-methylmalic acid

Compound C6HsN3°3 mw 167.12, N 25.15% was obtd by Quilico Fusco (Ref 2) as a white flocculent ppt, on treating the basic compd of probable formula O.N C(CH3).CH C.NH.CO.-CH2.NH2 with Na nitrite in AcOH. The basic compd was one the products obtained by Q F during investigation of reactions betw citraconic (methylmaleic) acid and nitric acid. The dried compd C6HsN303 exploded violently on heating. It is sol in cold aq alkalias alk carbonates and is decompd by hot alkalies mineral acids with the evoln of gas... 

E.51) (E.51) 2-Butenedioic acid, 2-methyl-, (Z)-, (Z)-2-methylbut-2-enedioic acid, citraconic acid, methylmaleic acid [498-23-7]... 

Citraconic Acid. 2-Methyi-2-butenedioic acid methylmaleic acid. C H604 mol wt 130.10. C 46.16%, H 4-65%, O 49.19%. Obtained by carefully heating citric acid at about 175. Production o( citraconic anhydride from ita -conic acid Humphrey. U.S. pat. 2.966,498 (i960 to Pfizer). 

The major by-products of this process are maleic anhydride, benzoic acid, and citraconic anhydride (methylmaleic anhydride). Maleic anhydride could be recovered economically. ... 

Citraconic anhydride (or 2-methylmaleic anhydride) is a derivative of maleic anhydride that is even more reversible after acylation than maleylated compounds. At alkaline pH values (pH 7-8) the reagent effectively reacts with amine groups to form amide linkages and a terminal carboxylate. However, at acid pH (3-4), these bonds rapidly hydrolyze to release citraconic acid and free the amine (Figure 1.86) (Dixon and Perham, 1968 Habeeb and Atassi, 1970 Klapper and Klotz, 1972 Shetty and Kinsella, 1980). Thus, citraconic anhydride has been used to temporarily block amine groups while other parts of a molecule are undergoing derivatization. Once the modification is complete, the amines then can be unblocked to create the original structure. 

Itaconic anhydride (2-propen-l,2-dicarboxylic anhydride) [2170-03-8] M 112.1, m 66-68°, 67-68°, 68°, b 139-140°/30mm. Crystd from CHCl3/pet ether. Can be distd under reduced press. Distn at atm press, or prolonged distn causes rearrangement to citraconic anhydride (2-methylmaleic anhydride). If the material (as seen in the IR spectrum) contains much free acid then heat with acetyl chloride or SOCI2, evaporate... 

In another reaction, conducted also in acetic acid, methylmaleic hydrazide (21, R = R2 = H, Ri = Me) has been isolated as the only product.If, however, a mixture of acetic acid and methanol were employed as solvent, citraconic and related anhydrides formed linear dihydrazides of type 23. A new type of reaction product, a A,A -biimide (26), has been established to result when dimethyl- or dichloromaleic anhydride were allowed to react with hydrazine in acetic acid with cooling. 

Citraconic anhydride (methylmaleic anhydride) [616-02-4] M 112,1, m 8-9 , b 109 /30mm, 132 /74mm, 213 /760mm, d 1.245, ng 1.472. Possible contamination is from the acid formed by hydrolysis. If the IR has OH bands, then reflux with AC2O for 30minutes, evaporate, then distil the residue in a vacuum, otherwise distil in a vacuum. Store in a dry atmosphere. [Vaughan Andersen J Am Chem Soc 77... 

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