Fumaric acid property

Physical Properties. Mahc acid crystallines from aqueous solutions as white, translucent, anhydrous crystal. The S(—) isomer melts at 100-103°C (1) and the R(+) isomer at 98-99°C (2). On heating, D,L-mahc acid decomposes at ca 180°C by forming fumaric acid and maleic anhydride. Under normal conditions, malic acid is stable under conditions of high humidity, it is hygroscopic. 

Table 1. Physical Properties of Maleic Anhydride, Maleic Acid, and Fumaric Acid...

Property Maleic anhydride Maleic acid Fumaric acid R(... 

Maleic and fiimaric acids have physical properties that differ due to the cis and trans configurations about the double bond. Aqueous dissociation constants and solubiUties of the two acids show variations attributable to geometric isomer effects. X-ray diffraction results for maleic acid (16) reveal an intramolecular hydrogen bond that accounts for both the ease of removal of the first carboxyl proton and the smaller dissociation constant for maleic acid compared to fumaric acid. Maleic acid isomerizes to fumaric acid with a derived heat of isomerization of —22.7 kJ/mol (—5.43 kcal/mol) (10). The activation energy for the conversion of maleic to fumaric acid is 66.1 kJ/mol (15.8 kcal/mol) (24). 

Fumaric Acid. Fumaric acid is used to acidify beverages for human consumption and has many iadustrial uses. Its acidic properties can cause skin and eye irritation. Fumaric acid combusts when exposed to heat or flame and can react vigorously with oxidizing agents. 

Vinyls. Vinyl resins are thermoplastic polymers made principally from vinyl chloride other monomers such as vinyl acetate or maleic anhydride are copolymerized to add solubUity, adhesion, or other desirable properties (see Maleic anhydride, maleic acid, and fumaric acid). Because of the high, from 4,000 to 35,000, molecular weights large proportions of strong solvents are needed to achieve appHcation viscosities. Whereas vinyls are one of the finest high performance systems for steel, many vinyl coatings do not conform to VOC requirements (see Vinyl polymers). 

Fractional crystallization, 413 Freezing point lowering, 325, 393 Freon, 362 Frequency of light, 246 relation to wave length, 251 Fructose, 423 Fumaric acid, 428 properties, 308 structure, 316... 

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

Property H H C=C HOOC COOH Maleic acid Maleic Acid H, COOH ooc "= Fumaric acid Fumaric Acid... 

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. 

Polyanhydrides based on unsaturated and fatty acid-derived monomers are shown in Table III. Poly(fumaric acid) (PFA) was fist synthesized by Domb et al. (1991) by both melt polycondensation and solution polymerization. The copolymer of fumaric acid and sebacic acid (P(FA-SA)) has been synthesized and characterized (Domb et al., 1991 Mathiowitz et al., 1990b). The mucoadhesive properties of this polymer... 

Competitive inhibitors bind to specific groups in the enzyme active site to form an enzyme-inhibitor complex. The inhibitor and substrate compete for the same site, so that the substrate is prevented from binding. This is usually because the substrate and inhibitor share considerable stmctural similarity. Catalysis is diminished because a lower proportion of molecules have a bound substrate. Inhibition can be relieved by increasing the concentration of substrate. Some simple examples are shown below. Thus, sulfanilamide is an inhibitor of the enzyme that incorporates j9-aminobenzoic acid into folic acid, and has antibacterial properties by restricting folic acid biosynthesis in the bacterium (see Box 11.13). Some phenylethylamine derivatives, e.g. phenelzine, provide useful antidepressant drags by inhibiting the enzyme monoamine oxidase. The cA-isomer maleic acid is a powerful inhibitor of the enzyme that utilizes the trans-isomer fumaric acid in the Krebs cycle. 

Double bonds are not freely rotatable (see p.4). If double-bonded atoms have different substituents, there are two possible orientations for these groups. In fumaric acid, an intermediate of the tricarboxylic acid cycle (see p. 136), the carboxy groups lie on different sides of the double bond (trans or E position). In its isomer maleic acid, which is not produced in metabolic processes, the carboxy groups lie on the same side of the bond (cis or Z position). Cis-trans isomers (geometric isomers) have different chemical and physical properties—e.g., their melting points (Fp.) and pl

Since they are diastereomers, cis-trans isomers always differ in properties the differences may range from very slight to considerable. The properties of maleic acid are so different from those of fumaric acid (Table 4.2) that it is not surprising that they have different names. 

TABLE 4.2 Some properties of maleic and fumaric acids... 

Other minor raw materials are used for specific needs. Fumaric acid [110-17-8], the geometric isomer of maleic acid, is selected to maximize thermal or corrosion performance and is the sole acid esterified with bisphenol A diol derivatives to obtain optimum polymer performance. Cycloaliphatics such as hydrogenated bisphenol A (HBPA) and cydohexanedimethanol (CHDM) are used in selective formulations for electrical applications. Tetrahydrophthalic anhydride [85-43-8] (THPA) can be used to improve resilience and impart useful air-drying properties to polyester resins intended for coating or lining applications. 

Maleic and fumaric acids have physical properties that differ due to the cis and trans configurations about the double bond. 

TABLE I. PHYSICAL PROPERTIES OF MALEIC ANHYDRIDE. MALEiC ACID. AND FUMARIC ACID... 

Maleic and phthalic anhydrides and fumaric acid are mainly used for polyester resin synthesis. However, dihydric alcohols such as ethylene and propylene glycols, diethylene, dipropylene, triethylene and neopentyl glycols, and hydrided or oxypropylened diphenylolpropane are also used.5 7 Different combinations of dibasic acids with diols allow us to vary the composition and properties of the resulting polyester resins over a wide range. 

Microspheres (10 to 200 pm in diameter) of poly(fumaric acid—cose-bacic acid) anhydride (20 80) [P(FA SA)] were shown to exhibit very strong and pronounced mucoadhesive properties both in vitro and in vivo.143 145 The microspheres were tested for their effect on GI transit of low-molecular-weight drugs salicylic acid and dicumarol. As compared with the control (drug-loaded alginate microspheres of similar size), the P(FA SA) microspheres significantly delayed the GI transit of these drugs in rats.145... 

Differences in spatial orientation might seem unimportant, but stereoisomers often have remarkably different physical, chemical, and biological properties. For example, the cis and trans isomers of butenedioic acid are a special type of stereoisomers called cis-trans isomers (or geometric isomers). Both compounds have the formula HOOC—CH=CH—COOH, but they differ in how these atoms are arranged in space. The cis isomer is called maleic acid, and the trans isomer is called fumaric acid. Fumaric acid is an essential metabolic intermediate in both plants and animals, but maleic acid is toxic and irritating to tissues. 

In an alkene such as ethene, the presence of the 7t-bond prevents rotation about the C=C bond. The hydrogen atoms on the separate carbons are either cis or trans to each other. When the alkene bears substituents on the separate carbon atoms, these are cis or trans to each other. Distinct geometric isomers are possible. These compounds have different properties. Thus c -ethenedicarboxylic acid is maleic acid (1.23). The carboxyl groups are close together in space and react together to form a cyclic anhydride (1.24). On the other hand, tranj-ethenedicarboxylic acid is fumaric acid (1.25) and no such interaction is possible. 

Reoall from Section 1.9B that there is restricted rotation around carbon-carbon double bonds. Maleic acid and fumaric acid are two isomers with vastly different physioal properties and pKg values for loss of both protons. Explain why each of these differenoes occurs. 

Stearyl fumarate is a half ester of fumaric acid with stearyl alcohol (octadeca-nol). Although stearyl fumarate might be expected to have dough-strengthening properties similar to those of SSL, this was not found to be so in practice, and the product was not a commercial success. Stearyl fumarate is still approved by the FDA for use in bread. 

A chiral C2-symmetric bridged ferrocene was constructed from a synthetic ligand containing two cyclopentadiene units (Fig. 4-12d). The key step in the synthesis of the ligand is a diastereoselective Diels — Alder reaction of anthracene with bis[(S)-l-ethoxycarbonylethyl]fumarate. When oxidized to the ferrocinium salt, the ferrocene derivative has Lewis acid properties and catalyzes Diels — Alder reactions with some enantioselectivity [85]. 

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