Adipic acid, decarboxylation

Formation of cyclopentanones by cyclization-decarboxylation of adipic acids r COjH... 

The photo-Kolbe reaction is the decarboxylation of carboxylic acids at tow voltage under irradiation at semiconductor anodes (TiO ), that are partially doped with metals, e.g. platinum [343, 344]. On semiconductor powders the dominant product is a hydrocarbon by substitution of the carboxylate group for hydrogen (Eq. 41), whereas on an n-TiOj single crystal in the oxidation of acetic acid the formation of ethane besides methane could be observed [345, 346]. Dependent on the kind of semiconductor, the adsorbed metal, and the pH of the solution the extent of alkyl coupling versus reduction to the hydrocarbon can be controlled to some extent [346]. The intermediacy of alkyl radicals has been demonstrated by ESR-spectroscopy [347], that of the alkyl anion by deuterium incorporation [344]. With vicinal diacids the mono- or bisdecarboxylation can be controlled by the light flux [348]. Adipic acid yielded butane [349] with levulinic acid the products of decarboxylation, methyl ethyl-... 

After two minor dust explosions in an industrial adipic acid dryer, evidence was obtained that adipic acid forms an iron complex capable of both decarboxylation/ dehydration of adipic acid to cyclopentanone and of catalysing air oxidation, giving exotherms from as low as 135°C. 

The thermal decarboxylation of a mixture of barium salts has been used to prepare unsymmetrical ketones the yields are not stated. The earlier procedure has been modified by carrying out the reaction in vacuo in an iron flask. Glass reaction vessels are inferior. In this manner, a large number of the high-molecular-weight methyl ketone s, C9, C,o, C,j-C , and C, are prepared in 54-67% yields. Cyclopentanone has been synthesized in 80% yield by distillation of adipic acid from barium hydroxide at 295°. In a study of metallic oxides and carbonates, magnesium oxide is preferred for the liquid-phase ketonization of stearic acid at 330-360° (95%). A convenient method for the preparation of dibenzyl ketone is the reaction of phenylacetic acid, acetic anhydride. 

As in other polycondensations at high temperatures, there are several side reactions that occur during the melt polycondensation of diamines and dicarboxylic acids. One has already been mentioned in Section 5.2 decarboxylation. As shown in the list of decarboxylation temperatures for a homologous series of dicarboxylic acids (Table 2), adipic acid begins to decarboxylate at around 300°C. In commercial practice, the maximum temperature that nylon-6,6 experiences during its preparation is about 290°C, so that decarboxylation is one of the most important degradation reactions of nylon-6,6. Nylon-6 and nylon-6,10 are more thermally stable than nylon-6,6. 

Primary, secondary, and tertiary acids can all be decarboxylated by this method. Adipic acid proved to be too sparingly soluble in benzene for satisfactory reaction but was decarboxylated in a mixture of benzene and sulfolane to give the iodide in 62% yield. 

Decarboxylation catalyst. The salt functions as a basic catalyst for the cyclization of adipic acid to cyclopentanone. The best yield (81%) was obtained when the... 

The synthesis of keto ester (17) and hence cyclopentanone itself from adipic acid (16) was introduced in Chapter 19. It (17) can be used to make other cyclopentanones by alkylation before decarboxylation. 

Dicarboxylic acids decarboxylate by attack of peroxy radicals on a-C— H bonds. The evidence for such a mechanism was obtained from data on the decarboxylation of adipic acid, with COOH and COOD groups, in oxidizing cumene, when the velocities of C02 production were found to be the same [299]. Carbon dioxide is produced from the acid in the initiated oxidation of cumene (Table 14) and cyclohexanol [215] after the induction period associated with the formation of an intermediate, probably a-hydroperoxide, after attack of peroxy radicals on a-C—H... 

Graphite X and graphite Y have been applied in a sequential microwave- irradiation-promoted decarboxylation of adipic acid with a reaction temperature of 450 °C (see Scheme 28) [51]. Under microwave conditions, for example, graphite X with its higher iron dispersion/content showed a 90% yield of a cy-... 

The preparation of adipodinitrile from adipic acid and ammonia is carried out industrially on a large scale in the gas phase by the fluidized-bed (BASF) and fixed-bed processes (ICI) (equation 1). Over the conventional catalysts, the selectivity is reduced by cyclization and simultaneous decarboxylation to form cyclopentanone, the reaction of that to yield cyclopentanoneimine and cyanocyclopetanoneimine (table 1). 

Experiments made on pyridoxal-deficient animals suggested that pyridoxal phosphate and iron are required for the biosynthesis of porphyrin. It was later established that pyridoxal phosphate is required for the formation of -amino levulinic acid, probably by participating in the formation of active glycine. The condensation of succinate and glycine leads to the formation of a very labile a-amino-j -keto adipic acid. The participation of a-amino-jS-keto adipic acid as an intermediate in the reaction was established in experiments proving the acid to be an efficient precursor of porphyrin biosynthesis in vitro. An enzyme system capable of catalyzing the succinyl CoA-glycine condensation and the decarboxylation of the intermediate to yield amino levulinic acid has also been obtained from a particular fraction of chicken erythrocyte. In liver, an enzyme has been found in the mitochondria [132]. 

Approximately thirteen cases of 2-aminoadipic aciduria have been reported in the literature. Nine of the reported patients excreted in addition more or less significant amounts of 2-oxoadipic acid, some also 2-hydroxy-adipic acid and variable amounts of glutaric acid. The latter results obviously from spontaneous decarboxylation of 2-oxoadipic acid. 

Order of thermal stabiUty as determined by differential thermal analysis is sebacic (330°C) > a2elaic = pimelic (320°C) > suberic = adipic = glutaric (290°C) > succinic (255°C) > oxahc (200°C) > malonic (185°C) (19). This order is somewhat different than that in Table 2, and is the result of differences in test conditions. The energy of activation for decarboxylation has been estimated to be 251 kj/mol (60 kcal/mol) for higher members of the series and 126 kJ/mol (30 kcal/mol) for malonic acid (1). 

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. 

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