Anions of dicarboxylic acids

Distortion due to an electrostatic field within the molecule may arise from the presence of free electric charges, e.g. in the anions of acid esters or in the singly-charged anions of dicarboxylic acids, or from the effect of one dipole field upon another. Only in exceptional cases will the fields of non-polar parts of the molecules affect the moment of a dipole by displacing electrons, so that they may be neglected here where they make themselves noticeable, their effect is essentially different and consists in a screening of the dipole field. 

The anions of substituted acids will not always react according to this scheme. Some of them, particularly the a-substituted acids, form unsaturated compounds. More complex reactions also occur when dicarboxylate ions COOCRCOO are used. When one of the carboxyl groups in the dicarboxylic acid is esterilied, the Kolbe reaction proceeds without difficulty ... 

Following the study of the simple coupling of radicals derived from the salt of a single carboxylic acid, it was found that the electrolysis of a mixture of carboxylate anions or of the salts of half esters of dicarboxylic acids increased the synthetic value of the method. This arises from the possibility of the formation of symmetrical and unsymmetrical coupled products of the derived radicals. These anodic syntheses are illustrated in the synthesis of hexacosane (Expt 5.11), sebacic acid (decanedioic acid), octadecanedioic acid and myristic acid (tetra-decanoic acid), in Expt 5.131. 

Data for the concentrations of dicarboxylic acid anions in formation waters from sedimentary basins are much more limited than for mono-carboxylic anions. Some of the reported values are controversial (Hanor et al., 1993 Kharaka et al., 1993a). The total reported range is 0-2,640 mg L (for discussion and references... 

Kharaka Y. K., Ambats G., and Thordsen J. J. (1993a) Distribution and significance of dicarboxylic acid anions in oil-field waters. Chem. Geol. 107, 499-501. 

Carbon monoxide reacts at atmospheric pressure with the radical anions of condenses aromatic hydrocarbons in ether solvents, e.g., the sodium-naphthalene-tetrahydro-furan system, is used for promoting the reduction of CO, to give products with new carbon-carbon bonds. Among the products with the naphthalene radical anion, dihydronaphthalene dicarboxylic acids and oxalic acid are isolated after oxidation with air and treatment with water. 

The crystalline acid salts of dicarboxylic acids so far described have been of Type A. Their hydrogen-anions are not well represented by the conventional formula (20), but rather by the over-elaborate (21). T) structures corresponding to (20) are not numerous amongst the acid... 

Few data are available on the concentration of dicarboxylic acid anions in subsurface waters. C2 through C q saturated acid anions have been reported in addition to maleic acid (cz5-butenedioic acid) (5. 15-16L Oxalic acid (ethanedioic) and malonic acid (propanedioic) appear to be the most abundant. Reported concentrations range widely from 0 to 2540 mg/1 but mostly are less than a few 100 mg/1. Concentrations of these species in formation waters are probably limited by several factors, including the very low solubility of calcium oxalate and calcium malonate (5), and the susceptibility of these dicarboxylic acid anions to thermal decomposition (16). This paper will focus on the monocarboxylic acids because they are much more abundant and widespread, and stability constants for their complexes with metals are better known. We do recognize that dicarboxylic acid anions may be locally important, especially for complexing metals. 

Chapter P, by Bell and Palmer, reviews experimental studies concerned with the decomposition of organic acids and their anions. In the absence of an effective catalytic surface, acetic acid may be expected to survive indefinitely. However, there are many potential catalysts. Laboratory determined activation energies for the decarboxylation of acetic acid varies from 34 to 170kJmol for stainless steel and titanium oxide, respectively. Reaction rates for the decarboxylation of dicarboxylic acids are extremely fast and uncomplexed acids are not likely to survive geologically significant lengths of time. However, the observed occurrence of dicarboxylic acids in some subsurface brines suggests the acids have been stabilized by complexation... 

The concentration of dicarboxylic acid anions from the High Island field, offshore Texas, was reported by Kharaka et al. (1985). They employed GC-... 

Table 1. Concentrations of dicarboxylic acid anions in formation water in Pleistocene reservoirs from High Island Field, offshore Louisiana. (After Kharaka et al. 1985)...

MS analysis of esterified organics to identify and quantify the dicarboxylic acids. The concentrations of dicarboxylic acid anions in the three samples with the highest concentrations of monocarboxylic acid anions are shown in Table 1. Succinate (butanedioic) and glutarate (penthanedioic) had the highest concentrations, 63 and 36 mg/1, respectively. Oxalate and malonate were below the detection limit of about lmg/1. Methybutanedioic and 2-methylpentaredioic acid anions were identified but not quantified. 

The highest concentrations of dicarboxylic acid anions are those reported by MacGowan and Surdam (1988) for the 12-31 well in the North Coles Levee field, San Joaquin Basin. They reported an oxalate concentration of 95 mg/1 and a malonate concentration of 2540 mg/1 in formation water from the 12-31 well. MacGowan and Surdam (1988) reported similarly high concentrations of oxalate and malonate for other wells in the San Joaquin and Santa Maria basins. Another analysis of organic acid concentrations in formation water from the 12-31 well was tabulated by MacGowan and... 

Decarboxylation of dicarboxylic acids is shown to be first-order with respect to total carboxylate and, like monocarboxylic acids, it is found that the rate for the acid form is faster than for the anionic form. However, unlike monocarboxylic acids, the overall rate in solutions of median pH is a linear function of the end-member rates. 

From the considerations above it may safely be concluded that only unrealistically large concentrations (thousands of ppm) of dicarboxylic acid anions combined with low pH values are likely to result in any significant increase in the amount of Al in solution above that which would otherwise be fixed by equilibrium between the pore fluid and clay minerals. 

Bengtsson, L. and Samuelson, O. (1971), Anion-exchange chromatography of dicarboxylic acids in sulphate medium. J. Chromatogr., 61,101. 

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