Oxalic acid, formation

Smith, V. M. On the Mechanism of Enzyme Action. XXXVI. Dehydrogenation Studies on Merulius lacrymans and Marasmius chordalis and the Mechanism of Oxalic Acid Formation. Arch. Biochem. 22, 275 (1949). 

At 0.3 MPa of oxygen, the sum of the observed C2 and C3 oxidation products amounted to correct mass balances, with glyceraldehyde, glyceric acid and oxalic acid being the dominant products in absence of added NaOH [81]. NaOH addition resulted in the disappearance of oxalic acid formation. 

Oxalic acid, formation, 43 421-422 Oxalyl fluoride, reaction with hexafluoroace-tone, 30 271... 

Chromatographic analysis of reaction products of citric acid synthesized by fixed cells reveals the presence of products generated from side reactions. They include isocitric acid, oxalic acid and trace quantities of gluconic acid. Isocitrate is perhaps the major one, amounting to as much as 15 to 20% of citrate. Oxalic acid formation in citric acid fermentations is reported to be dependent both on pH and on the extent of aeration. By proper control of pH and dissolved oxygen levels, it might be possible to reduce the formation of oxalate. 

If an accurate knowledge of the individual steps of the metabolic pathways leading to oxalic acid formation is necessary to understand oxaluria, an evaluation of the relative importance of each of these pathways in metabolism is of no less interest. In that respect, it is significant that under normal conditions the addition of 25-100 g of glycine to the diet does not affect of oxalic acid excretion. In contrast, the inclusion of 40 g of gelatin (corresponding to 10 g of glycine) doubles the amount of oxalic acid excreted. 

Certain aliphatic compounds are oxidised by concentrated nitric acid, the carbon atoms being split off in pairs, with the formation of oxalic acid. This disruptive oxidation is shown by many carbohydrates, e.g., cane sugar, where the chains of secondary alcohol groups, -CH(OH)-CH(OH)-CH(OH)CH(OH)-, present in the molecule break down particularly readily to give oxalic acid. 

CH2(0H)CH(0H)CH2(0H) + HCOOH reaches about 100°, losing carbon dioxide and giving glyceryl monoformate (B). On further heating, particularly if more oxalic acid is added, the mono formate is hydrolysed (the necessary water being provided both by the oxalic acid and by the first reaction), and consequently a distillate of aqueous formic acid is obtained. 

Note. Methyl oxalate, unlike most other esters, hydrolyses very rapidly in aqueous solution hence it will evolve CO in the above test, owing to the formation of methanol and free oxalic acid. 

The presence of formates, oxalates, formic acid, and oxalic acid in the carbonylation of alkynes affects the regioselectivity. Also, the regioselectivity can be controlled to some extent by the proper selection of the ligands. A linear a,... 

J-unsaturated ester is formed from a terminal alkyne by the reaction of alkyl formate and oxalate. The linear a, /J-unsaturated ester 5 is obtained from the terminal alkyne using dppb as a ligand by the reaction of alkyl formate under CO pressure. On the other hand, a branehed ester, t-butyl atropate (6), is obtained exclusively by the carbonylation of phenylacetylene in t-BuOH even by using dppb[10]. Reaction of alkynes and oxalate under CO pressure also gives linear a, /J-unsaturated esters 7 and dialkynes. The use of dppb is essen-tial[l 1]. Carbonylation of 1-octyne in the presence of oxalic acid or formic acid using PhiP-dppb (2 I) and Pd on carbon affords the branched q, /J-unsatu-rated acid 8 as the main product. Formic acid is regarded as a source of H and OH in the carboxylic acids[l2]. 

Oxidation. Maleic and fumaric acids are oxidized in aqueous solution by ozone [10028-15-6] (qv) (85). Products of the reaction include glyoxyhc acid [298-12-4], oxalic acid [144-62-7], and formic acid [64-18-6], Catalytic oxidation of aqueous maleic acid occurs with hydrogen peroxide [7722-84-1] in the presence of sodium tungstate(VI) [13472-45-2] (86) and sodium molybdate(VI) [7631-95-0] (87). Both catalyst systems avoid formation of tartaric acid [133-37-9] and produce i j -epoxysuccinic acid [16533-72-5] at pH values above 5. The reaction of maleic anhydride and hydrogen peroxide in an inert solvent (methylene chloride [75-09-2]) gives permaleic acid [4565-24-6], HOOC—CH=CH—CO H (88) which is useful in Baeyer-ViUiger reactions. Both maleate and fumarate [142-42-7] are hydroxylated to tartaric acid using an osmium tetroxide [20816-12-0]/io 2LX.e [15454-31 -6] catalyst system (89). 

In acidic solution, the degradation results in the formation of furfural, furfuryl alcohol, 2-furoic acid, 3-hydroxyfurfural, furoin, 2-methyl-3,8-dihydroxychroman, ethylglyoxal, and several condensation products (36). Many metals, especially copper, cataly2e the oxidation of L-ascorbic acid. Oxalic acid and copper form a chelate complex which prevents the ascorbic acid-copper-complex formation and therefore oxalic acid inhibits effectively the oxidation of L-ascorbic acid. L-Ascorbic acid can also be stabilized with metaphosphoric acid, amino acids, 8-hydroxyquinoline, glycols, sugars, and trichloracetic acid (38). Another catalytic reaction which accounts for loss of L-ascorbic acid occurs with enzymes, eg, L-ascorbic acid oxidase, a copper protein-containing enzyme. 

Oxidative Garbonylation. Carbon monoxide is rapidly oxidized to carbon dioxide however, under proper conditions, carbon monoxide and oxygen react with organic molecules to form carboxyUc acids or esters. With olefins, unsaturated carboxyUc acids are produced, whereas alcohols yield esters of carbonic or oxalic acid. The formation of acryUc and methacrylic acid is carried out in the Hquid phase at 10 MPa (100 atm) and 110°C using palladium chloride or rhenium chloride catalysts (eq. 19) (64,65). 

Dry air is blown through the solution to remove the excess of ammonia, and the solution is then dissolved in its own volume of absolute alcohol. A sample of this solution is titrated with standard oxalic acid, litmus being used as an outside indicator (Note 3). The amount of oxalic acid (Note 4) necessary to form the acid salt is placed in a large evaporating dish and dissolved in 4 1. of 95 per cent alcohol. The amine solution is then slowly run into the acid with constant stirring. During the addition of the last half of the amine solution, the container must be cooled in order to avoid the formation of the neutral oxalate,... 

In context with the formation of peraminosubstituted 1,4,5,8-tetraazaful-valenes of type 85 it must be mentioned that the bis-vinylogous compounds 94 can be easily prepared by reaction of acetamidine with bisimidoylchlo-rides derived from oxalic acid (96S1302). In the course of a complex reaction a cyclic ketene aminal was produced it immediately underwent an oxidative dimerization to yield deeply colored TAFs. Tlieir high chemical stability can be compared with that of indigoid dyes and manifests itself, for example, by the fact that they are soluble in hot concentrated sulfuric acid without decomposition. Tire same type of fulvalene is also available by cy-... 

On the other hand, the decrement in grafting observed with oxalic acid is higher than that observed with sulfuric acid. This can be due to the fact that oxalic acid is more active than sulfuric acid for the formation of free radicals and, consequently, the grafting in the presence of oxalic acid is greater than in the presence of sulfuric acid. 

Potassium Oxalata. K2C2 04. HjO, mw 184.23 colorl, odorless crysts mp, loses H20 at about 160°, when iguited is converted into carbonate without appreciable charring d 2.13g/cc, sol in 3p of w. Can be prepd by heating a mixt of K formate or carbonate with oxalic acid and a small amt of K hydroxide, with subsequent extraction of w. Highly toxic by inhalation and ingestion... 

Oxalic acid was formerly manufd by fusion of cellulose matter, eg sawdust, with Na hydroxide or by oxidation with nitric acid. It is now made by passing CO into coned Na hydroxide or by heating Na formate in the presence of Na hydroxide or Na carbonate (Refs 1 2)... 

Oxalic acid is caustic and corrosive to the skin and mucous membranes. Ingestion may cause severe gastroenteritis with vomiting, diarrhea and melana. Renal damage can occur as result of formation of excessive Ca oxalate. Severe poisoning can end fatally. Tolerance,... 

The kinetics of the Ce(IV) sulphate oxidation of oxalic acid are simple second order although the rate coefficient is inversely proportional to both hydrogen and bisulphate-ion concentrations, and it is also reduced at very high oxalic acid concentrations. Values of the activation energy from 13.4+1.5 (ref. 411) to 16.5+0.4 (ref. 409) kcal.mole have been reported. An intermediate has been detected spectroscopically " this decays in first-order fashion with E = 10.5+0.5 kcal.mole" and with a rate independent of acidity. However, the extent of formation of this complex is reduced as the acidity is increased ", and it appears that a less reactive dioxalato complex is formed at higher substrate concentrations ". 

Admixture of the reactants caused the pink colour of NpO to change to yellow, suggesting complex formation, and one mole of oxalic acid consumed four moles of oxidant to give Np(V) as the final product, identified optically, k is independent of ionic strength and is 0.012 + 0.001 sec at 25 °C ( = 1 M) with E = 15.5 kcal.mole . Breakdown of an oxalatoneptunium(VI) complex of low formation constant is presumably the mechanism. 

A general problem during the syntheses of A9-THC is the formation of the thermodynamically more stable A8-THC, which reduces the yield of A9-THC. It is formed from A9-THC by isomerization under acidic conditions. While the usage of strong acids such as p-TSA or TEA leads mainly to A8-THC, the yield of A9-THC can be increased by employment of weak acids, e.g., oxalic acid [70]. 

The effect of an aqueous solution of sodium chlorite on oxalic acid in the presence of sunlight gives rise to a violent detonation, which is supposedly due to the formation of chlorine dioxide that is unstable ... 

This reaction involves formation of a mixed anhydride-chloride of oxalic acid, which then decomposes, generating both C02 and CO. 

Langer and coworkers constructed diverse O- and N-heterocydic scaffolds, such as y-alkylidene-a-hydroxybutenolides and pyrrolo[3,2-b]pyrrol-2,5-diones, exploiting the well-established cyclization strategy of bisnucleophiles with oxalic acid derivatives [163], while Stockman s research group reported in this context on a novel oxime formation/Michael addition providing the structural core of the alkaloid perhydrohistrionicotoxin [164]. 

The formation of lipid components in an aqueous phase at temperatures from 370 to 620 K was studied by Rushdie and Simoneit (2001), who heated aqueous solutions of oxalic acid in a steel vessel for 2 days the yield of oxidized compounds reached a maximum (5.5% based on oxalic acid) between 420 and 520 K. A broad spectrum of compounds was obtained, from n-alkanes to the corresponding alcohols, aldehydes and ketones. At higher temperatures, i.e., above 520-570 K, cracking reactions competed with the synthetic reactions. 

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