Maleic and fumaric acids

Maleic acid may be prepared by warming malic acid with acetyl chloride, distilling the mixture under atmospheric pressure to isolate maleic anhydride, and hydrolysing the latter by boiling with water. 

Commercially, maleio anhydride is prepared more cheaply by the catalytic vapour phase oxidation (in the presence of vanadium pentoxide at about 400°) of benzene with atmospheric oxygen  

Upon heating with hydrochloric acid, maleic acid, m.p. 144°, is converted into fumaric acid, m.p. 287°  

Maleic acid Fumaric acid Succinic acid 

Both acids yield succinic acid, m.p. 185°, upon catalytic reduction (see Section 111,150), thus establishing their structures. Maleio and fumaric acids are examples of compounds exhibiting eis - trans isomerism (or geometric isomerism). Maleic acid has the cis structure since inter alia it readily yields the anhydride (compare Section 111,93). Fumario acid possesses the tram structure it does not form an anhydride, but when heated to a high temperature gives maleic anhydride. 

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Aqueous titration with IN sodium hydroxide is the usual malic acid assay. Maleic and fumaric acid are deterrnined by a polarographic method. Analytical methods have been described (40). 

Acid Chloride Formation. Monoacid chlorides of maleic and fumaric acid are not known. Treatment of maleic anhydride or maleic acid with various reagents such as phosgene [75-44-5] (qv), phthaloyl chloride [88-95-9] phosphoms pentachloride [10026-13-8] or thionyl chloride [7719-09-7] gives 5,5-dichloro-2(5JT)furanone [133565-92-1] (4) (26). Similar conditions convert fumaric acid to fumaryl chloride [627-63-4] (5) (26,27). NoncycHc maleyl chloride [22542-53-6] (6) forms in 11% yield at 220°C in the reaction of one mole of maleic anhydride with six moles of carbon tetrachloride [56-23-5] over an activated carbon [7440-44-4] catalyst (28). 

Oxidation. Maleic and fumaric acids are oxidized in aqueous solution by ozone [10028-15-6] (qv) (85). Products of the reaction include glyoxyhc acid [298-12-4], oxalic acid [144-62-7], and formic acid [64-18-6], Catalytic oxidation of aqueous maleic acid occurs with hydrogen peroxide [7722-84-1] in the presence of sodium tungstate(VI) [13472-45-2] (86) and sodium molybdate(VI) [7631-95-0] (87). Both catalyst systems avoid formation of tartaric acid [133-37-9] and produce i j -epoxysuccinic acid [16533-72-5] at pH values above 5. The reaction of maleic anhydride and hydrogen peroxide in an inert solvent (methylene chloride [75-09-2]) gives permaleic acid [4565-24-6], HOOC—CH=CH—CO H (88) which is useful in Baeyer-ViUiger reactions. Both maleate and fumarate [142-42-7] are hydroxylated to tartaric acid using an osmium tetroxide [20816-12-0]/io 2LX.e [15454-31 -6] catalyst system (89). 

Finally, the techniques of nmr, infrared spectroscopy, and thin-layer chromatography also can be used to assay maleic anhydride (172). The individual anhydrides may be analyzed by gas chromatography (173,174). The isomeric acids can be determined by polarography (175), thermal analysis (176), paper and thin-layer chromatographies (177), and nonaqueous titrations with an alkaU (178). Maleic and fumaric acids may be separated by both gel filtration (179) and ion-exchange techniques (180). 

K. Lohbeck and co-workers, "Maleic and Fumaric Acids," iu Ullmann s Enyclopedia of Industrial Chemisty, Vol. A16, 5th ed., VCH, Weinheim, Germany,... 

Removal of maleic and fumaric acids from the cmde malononitrile by fractional distillation is impractical because the boiling points differ only slightly. The impurities are therefore converted into high boiling compounds in a conventional reactor by means of a Diels-Alder reaction with a 1,3-diene. The volatile and nonvolatile by-products are finally removed by two vacuum distillations. The by-products are burned. The yield of malononitrile amounts to 66% based on cyanogen chloride or acetonitrile. 

Pyrroles react at free a- or -positions with acetylenedicarboxylic acid or the methyl ester yielding mixtures of the corresponding maleic and fumaric acid derivatives. Protons are readily available to satisfy... 

Maleic and fumaric acids are cis- and irons- Maleic acid gives up its first proton more readily isomers having two carboxyl groups, than does fumaric acid. However, the opposite... 

Examples of polyfunctional carboxylic acids esterified by this method are shown in Table I. Yields are uniformly high, with the exception of those cases (maleic and fumaric acids) where some of the product appears to be lost during work-up as a result of water solubility. Even with carboxylic acids containing a second functional group (e.g., amide, nitrile) which can readily react with the oxonium salt, the more nucleophilic carboxylate anion is preferentially alkylated. The examples described in detail above illustrate the esterification of an acid containing a labile acetoxy group, which would not survive other procedures such as the traditional Fischer esterification. 

TABLE 4.2 Some Properties of Maleic and Fumaric Acids... 

However, if both maleic and fumaric acid gave the dl pair or a mixture in which the dl pair predominated, the reaction would be stereoselective but not stereospecific. If more or less equal amounts of dl and meso forms were produced in each case, the reaction would be nonstereoselective. A consequence of these definitions is that if a reaction is carried out on a compound that has no stereoisomers, it cannot be stereospecific, but at most stereoselective. For example, addition of bromine to methylacetylene could (and does) result in preferential formation of trans-1,2-dibromopropene, but this can be only a stereoselective, not a stereospecific reaction. 

Co(lII) perchlorate oxidations of succinic, aspartic, maleic and fumaric acids all obey the rate expression ... 

Detailed studies of 1 1 complex formation between and maleic and fumaric acids, which precedes reduction to succinic acid, cis-trans isomerisation and exchange of the double bond hydrogens, are relevant to the complex kinetics (A = substrate)... 

Allyl alcohol Crotonaldehyde P -Dimethylacrylic acid Maleic and fumaric acids. ... 

Figure 8 Separation of isomeric acids (maleic and fumaric acid) by controlled surface porosity anion exchange chromatography. Column Sulfonated fluoropolymer coated onto a 50-p glass bead. Average pore size about 1000 A. Flow rate 2.73 ml/min. Eluant 10 mM HN03. Temperature 60°C. Detection absorbance. (Reproduced from Kirkland, J. J., J. Chromatogr. Sci., 7,361,1969. By permission of Preston Publications, A Division of Preston Industries, Inc.)...

Fig. 4.5. Potentiometric titration of maleic and fumaric acid. Titrant (C4H9)3CH3NOH, 0.1 N in pyridine glass-calomel electrode (pyridine).

Many derivatives of maleic and fumaric acid are known to undergo photosensitized dimerization.<121> Some derivatives of maleic acid are as follows ... 

Elving, Rosenthal, Hayes and Martin 41> studied the electrochemical reduction of bromofumaric acid(27) and bromomaleic acid(28)in aqueous solution over a wide pH range. It was claimed that reduction of 27 proceeds stereo-specifically to fumaric acid, and that reduction of 28 affords mixtures of maleic and fumaric acids. Because of the polar and hydrogen-bonding properties of the carboxyl groups in 27 and 28, the relation of these results to those of Fry and Mitnick l6) is unclear. 

Some experiments were conducted to determine the influence of the solution pH. The catalytic oxidation of p-coumaric acid has been performed by increasing the initial pH from 3.5 to 7.5 and 11. Although the cleavage of the exocyclic double bond may be pH sensitive we obtained the same major intermediates which are the hydroxybenzaldehyde and the p-hydroxybenzoic acid molecules. The rate of oxidation of these aromatic compounds to ring opening compounds was higher when the initial pH was basic and yielded higher concentrations of maleic and fumaric acids. 

Let us take maleic and fumaric acids. The values of the first and second dissociation ... 

Whereas in benzene and in its derivatives the six substituents lie in the same plane, namely, that of the ring, they are distributed in cyclohexane in two planes parallel to that of the ring. Hence there results a special type of spatial isomerism when two hydrogen atoms united to different carbon atoms are replaced. The isomerism is caused by the position of the two substituents, for they may lie in the same plane (m-form), or one in each plane (iraws-form). The phenomenon is closely related to the cis-trans isomerism of the ethylenes, of which the best-known example is that of maleic and fumaric acids. 

In a model the isomerism is seen to be of the same kind as that of maleic and fumaric acids. 

For the analogues of maleic and fumaric acid, we choose the C -C distance to be 1.34 A and fix the angle ( > = 0 and ( ) = 7t, respectively. If it is assumed that for these molecules the proton-proton correlation is purely electrostatic, then we can write... 

In aqueous hydrochloric acid solutions, mthenium(II) chloride catalyzed the hydrogenation of water-soluble olefins such as maleic and fumaric acids [6]. After learning so much of so many catalytic hydrogenation reactions, the kinetics of these simple Ru(II)-catalyzed systems still seem quite fascinating since they display many features which later became established as standard steps in the mechanisms of hydrogenation. The catalyst itself does not react with hydrogen, however, the mthenium(II)-olefin complex... 

Let us consider now the origin of the effect of varying solvent composition on the hydrogenation rate in diglyme-water mixtures. The key to the explanation comes from the study of the effect of pH on the rate of hydrogenation of maleic and fumaric acids in homogeneous aqueous solutions. Fig. 3.2.a and 3.2.b show these rates as a function of pH together with the concentration distribution of the undissociated (H2A), half dissociated (HA ) and fully dissociated (A ) forms of the substrates [86]. 

The reactions enumerated lead to the adducts that are observable by means of the ESR method. In the cases of maleic and fumaric acids, ESR spectra can be recorded at high enough pH values only Being a strong electrophile, radical SO4 is more active toward a carboxylate ion than to neutral molecules of unsaturated acids. 

The cycloaddition of allenes to symmetrically disubstituted alkenes gives mixtures of cyclobutanes with stereochemical equilibration of the substituents. The reaction of 1,3-dimethylallenc with either diethyl fumarate or diethyl maleate produces a mixture of the /raw.v-bis(ethoxycar-bonyl)cyclobutanes.s The same nonstereoselectivity was observed for phenylallene and 1,1-dimelhylallene cycloadditions to maleic and fumaric acid diesters.9 10... 

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