Fumaric acid, occurrence

Crude opium. Opium crudum, Pharm. Eur. has a morphine content of 12-16% whereas the pharmacopoeias require 10%. The alkaloids are bound to meconic acid, lactic acid, fumaric acid and sulphuric acid. Opium has a very characteristic smell and can be identified microscopically by the occurrence of characteristic fragments from the wall of the capsule. 

Addition of a small proportion of iron (II) sulfate to D-tartaric acid-hydrogen peroxide causes rapid conversion into a product closely related to dihydroxymaleic acid. Occurrence of a reaction with substituted hydrazines indicates the presence of a keto acid (1), and isolation of a diacetate and a dibenzoate favors the hypothesis of formation of dihydroxy-fumaric acid (2). On the basis of pH studies, Hatcher and Sturrock ... 

Structure X in Figure 300 shows interpenetrating tetrahedra with carbon centers and a single bond between these carbons. Van t Hoff correctly postulated that there is free rotation about such single bonds. Structures XIa, Xlb, XII, and XIII rationalize cis and Irons isomerism (e.g., the difference between maleic acid and fumaric acid). Structure XIV explains the widespread occurrence of six-membered rings in chemistry and aspects of Baeyer s strain theory. ... 

Homoserine also has been detected in filtrates of liver preparations incubated with methionine. Cantoni provisionally identified homoserine as a product of the acid hydrolysis of active methionine (S-adeno-sylmethionine). Beyond homoserine, the postulated reactions 2 and 3 are still more speculative. It might be presumed that homoserine is oxidized to aspartic acid, in analogy to the observations on the catabolism of lysine, in which the analogous a-amino adipic acid is an intermediate. If aspartic acid is formed, the subsequent reaction sequence is readily apparent. Evidence favorable to the proposed reaction pathway is the finding of Marshall and Friedberg, of the occurrence of a small amount of fumaric acid, labeled in the methine carbons, from the livers of mice injected with DL-methionine-2-C. ... 

Pucher, Sherman, and Vickery ) and for malic acid (method of Nossal ), every one was found to contain measurable quantities. The occurrence of succinic acid has also been widely reported. Isocitric and fumaric acids have been found in many materials but not in all. Negative findings were probably often due to the absence of sensitive and specific methods of detection. 

Occurrence of the stereo isomers, known as maleic and fumaric acids, has been interpreted for a long time as evidence of a barrier to rotation around a double bond. It is of interest to note that this steric rigidity is consistent with the orientation of Victor Meyer s affinity centers and with the Lewis model of electron pairs. 

The predominant gaseous products of the decomposition [1108] of copper maleate at 443—613 K and copper fumarate at 443—653 K were C02 and ethylene. The very rapid temperature rise resulting from laser heating [1108] is thought to result in simultaneous decarboxylation to form acetylene via the intermediate —CH=CH—. Preliminary isothermal measurements [487] for both these solid reactants (and including also copper malonate) found the occurrence of an initial acceleratory process, ascribed to a nucleation and growth reaction. Thereafter, there was a discontinuous diminution in rate (a 0.4), ascribed to the deposition of carbon at the active surfaces of growing copper nuclei. Bassi and Kalsi [1282] report that the isothermal decomposition of copper(II) adipate at 483—503 K obeyed the Prout—Tompkins equation [eqn. (9)] with E = 191 kJ mole-1. Studies of the isothermal decompositions of the copper(II) salts of benzoic, salicylic and malonic acids are also cited in this article. 

Ogston has recently put forward an idea which removes the difficulty of ascribing both reactions to one enzyme. It is a development of his theory discussed above of a three-point combination between enzyme and substrate. As already explained, the fumarate molecule in order to yield optically active malic acid must be so placed on the enzyme surface that only one double-bond component can react, but no direction need be exerted on the water in which H and OH are distributed. If it is now assumed that aconitase is constructed analogously to fumarase in that again no direction is exerted on the elements of water when they combine with aconitic acid, it is seen at once that two different compounds arise, namely, citric and isocitric acids. The occurrence of the reverse reaction would follow from the requirement of catalytic reversibility. 

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