Aqueous reactions succinic acid

Miscellaneous Reactions. Radiolysis at room temperature of diluted aqueous solutions of succinic acid produces 1,2,3,4-butane tetracarboxyhc acid [1703-58-8] (122), which has numerous industrial and agricultural appHcations (eq. 12). 

A mixture consisting of 8 grams of estriol, 20 grams of succinic acid anhydride and 60 ml of pyridine is heated at 90 C for 4 hours, after which the reaction mixture is poured into water. The aqueous solution is extracted with ether, the ether layer is separated, washed with diluted sulfuric acid and after that with water until neutral, then evaporated to dryness to obtain 14 grams of an amorphous substance. Melting point 82° to 86°C. This drying residue proves to consist of a mixture of estriol disuccinate and estriol monosuccinate, which are separated by repeated crystallization from a mixture of methanol and water. 

Aqueous NaOCl (10%, 400 ml) is added with stirring to the cycloalkanone (0.1 mol) and Aliquat (4 g, 10 mmol) at 10°C. The mixture is stirred and the pH is maintained at 12.0 by the addition of aqueous NaOH (0.5 M). On completion of the reaction, the aqueous phase is separated, washed with CH2C12 (200 ml), and acidified to pH 2.0 with HC1 (2M). The acidic solution is cooled to 0°C to cause precipitation of the dicarboxylic acids (e.g. cyclohexanone yields a mixture of adipic acid 63%, succinic acid 9%, glutaric acid 17%, and a,a-dichloroadipic acid 5%). 

The evidence for the formation of complex heteropoly-acids with tantalic acid is very comparable to that set forth in the case of niobic acid (see p. 165). Solutions of tantalates are readily hydrolysed in aqueous solution by boiling, and even more readily by the addition of mineral acids, acetic acid or succinic acid in the presence, however, of arsenious add, arsenic add, tartaric add or dtric add no precipitation of tantalic add takes place. Again, tincture of galls yields a yellow predpitate with solutions of tantalates which have been rendered feebly acid with sulphuric add this reaction does not, however, take place in the presence of ordinary tartaric add, racemic add or citric acid. Tartaric add also prevents the formation of the predpitates which are thrown down on the addition of potassium ferrocyanide or potassium ferricyanide to faintly acid solutions of tantalates, and hinders the precipitation of tantalic add from solutions in inorganic acids by the action of ammonia. In all these cases it is assumed that complex acids or their salts are produced, in consequence of which the usual reaction does not take place. 

In some cases, substrates and enzymes are not soluble in the same solvent. To achieve efficient substrate conversion, a large interface between the immiscible fluids has to be established, by the formation of microemulsions or multiple-phase flow that can be conveniently obtained in microfluidic devices. Until now only a couple of examples are published in which a two-phase flow is used for biocatalysis. Goto and coworkers [431] were first to study an enzymatic reaction in a two-phase flow in a microfluidic device, in which the oxidation ofp-chlorophenol by the enzyme laccase (lignin peroxidase) was analyzed (Scheme 4.106). The surface-active enzyme was solubilized in a succinic acid aqueous buffer and the substrate (p-chlorophenol) was dissolved in isooctane. The transformation ofp-chlorophenol occurred mainly at... 

Some preliminary tests were performed on aqueous solutions of succinic acid to evaluate the best operating parameters to carry out this reaction, using the 5% Ru/C catalyst. The study of the effect of temperature up to 200°C indicated a strong temperature dependence of the oxidation rates. Thus, the TOC abatement was more than 99 % after 4 hours at 190°C, while it was only 77.5% at 180°C. The apparent activation energy, deduced from the Arrhenius plot between 180 and 200°C, was ca. 100 kJ mol. ... 

Figure 1. Oxidation of an aqueous solution of succinic acid (43 mmol.r ) over 5 wt% Ru/C a) yield of succinic acid and intermediate products vs. time and b) TOC removal and pH profile vs. time. Reaction conditions 190°C, air, 5 MPa total pressure.

In the basic solution (run 5), the reaction rate was greatly reduced and the amount of acetic acid still increased. These results indicate that the oxidation may occur preferentially on the undissociated forms of the acids (pK, of succinic acid = 4.16, pKj = 5.61), rather than on the carboxylate ions, in agreement with previous results on selective oxidation of aqueous solutions of alcohols over noble metal catalysts. Slightly basic conditions favor the desorption of the acid salt from the surface and prevents C-C bond rupture and over-oxidation, whereas acidic pH favor the adsorption of the carboxylic acid and its further oxidation [14-15]. Similar results were observed by Imamura, et al. [11] in the oxidation of formic acid or acetic acid over 5 % Ru/CeOj. 

Wet air oxidation in the presence of carbon-supported ruthenium provides an efficient method for total destruction by air of organic acid pollutants in aqueous solutions. In the presence of high concentrations of NaCl salts or of mineral acids, the oxidation of succinic acid was not modified, whereas the rate of oxidation of acetic acid formed transiently, was slightly lowered. In neutral and basic media, the oxidation of the carboxylate ions was greatly decreased. No leaching of ruthenium was observed, which means that the reaction was catalyzed by a heterogeneous catalytic system. However, the carbon support was partially oxidized, which limits the application of this catalytic system for the CWAO of acetic acid, which requires temperatures close to 200°C. 

Mono- or dialkyl esters of succinic acid are formed by the addition of fatty alcohols or ethoxylated fatty alcohols to maleic anhydride in the presence of acid catalysts. These are the hydrophobic starting material for sulfosuccinates. The next step is the addition of sodium hydrogensulfite in aqueous methanol, which forms the surface-active sulfosuccinates via a radical reaction. 

At the pH of the aqueous environment in the cells, the carboxylic acids are ionized, which means it is actually the carboxylate ions that take part in the reactions of the citric acid cycle. For example, in water, succinic acid is in equilibrium with its carboxylate ion, succinate. 

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