Oxalic acid, decomposition

This is not energetically reasonable since the enthalpy change for such a process is probably > 65 kcal.mole". Lapidus et subsequently studied deuterium and isotope effects in the oxalic acid decomposition. The deuterium effect (kiilko) was found to vary from 1.3 (400 °K) to 0.87 (435 °K), a reverse isotope effect. A similar reversal was found in the study, viz. 

Decomposition Curve. The refinements in the analytical procedure permitted a more accurate determination of the oxalic-acid decomposition curve. The experimental data demonstrated that the yield decreases continuously with increasing dose throughout the decomposition range. A decomposition curve for a 100 mM oxalic-acid solution obtained at Riso is shown in Figure 2. 

Figure 2. Calibration curve for oxalic-acid decomposition vs. absorbed dose as determined by titration and by spectrophotometry for 100 raM oxalic acid...

Figure 3a. Calibration curves for oxalic-acid decomposition (log c0/c vs. absorbed dose) obtained at Natick, Riso and Vinca (Ref. 18)...

Organic Solids A few organic compounds decompose before melting, mostly nitrogen compounds azides, diazo compounds, and nitramines. The processes are exothermic, classed as explosions, and may follow an autocatalytic law. Temperature ranges of decomposition are mostly 100 to 200°C (212 to 392°F). Only spotty results have been obtained, with no coherent pattern. The decomposition of malonic acid has been measured for both the solid and the supercooled liquid. The first-order specific rates at 126.3°C (259.3°F) were 0.00025/min for solid and 0.00207 for liquid, a ratio of 8 at II0.8°C (23I.4°F), the values were 0.000021 and 0.00047, a ratio of 39. The decomposition of oxalic acid (m.p. I89°C) obeyed a zero-order law at 130 to I70°C (266 to 338°F). 

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-... 

Its disemicarbazone, CjgHjgNgOj, melts at 228° C. with decomposition.. The diketone regenerated by the action of oxalic acid on the disemicarbazone has the following properties —... 

The brilliant emissions resulting from the oxidation of certain oxalic acid derivatives, especially in the presence of a variety of fluorophores, are the bases of the most active area of current interest in CL. This group of chemiluminescent reactions has been classified as peroxyoxalate chemistry because it derives from the excited states formed by the decomposition of cyclic peroxides of oxalic acid derivatives called dioxetanes, dioxetanones, and dioxetanediones. 

Following earlier studies of the oxidation of formic and oxalic acids by pyridinium fluoro-, chloro-, and bromo-chromates, Banerji and co-workers have smdied the kinetics of oxidation of these acids by 2, 2Tbipyridinium chlorochromate (BPCC) to C02. The formation constant of the initially formed BPCC-formic acid complex shows little dependence on the solvent, whilst a more variable rate constant for its decomposition to products correlates well with the cation-solvating power. This indicates the formation of an electron-deficient carbon centre in the transition state, possibly due to hydride transfer in an anhydride intermediate HCOO—Cr(=0)(0H)(Cl)—O—bpyH. A cyclic intermediate complex, in which oxalic acid acts as a bidentate ligand, is proposed to account for the unfavourable entropy term observed in the oxidation of this acid. 

X 10mol/L). Both experiments were conducted at 25 °C. The decomposition rate of 4-nitro-aniline was very high by the photo-Fenton reaction in comparison to titanium dioxide-UV light (k = 365 nm). Decomposition products identified in both reactions were nitrobenzene, p-benzoquinone, hydroquinone, oxalic acid, and resorcinol. Oxalic acid, hydroquinone, and p-benzoquinone were identified as intermediate products using HPLC. 

Reactions in aqueous phase are similar to those of barium chloride. When treated with sulfuric acid, hydrofluoric acid, phosphoric acid or oxalic acid, the insoluble barium salts of these anions are formed. Similarly, many insoluble barium salts may form by double decomposition reactions when treated with soluble salts of other metals. 

From the very good activity of thermally or electrochemically activated CoTAA for the reaction of CO one might deduce that the oxidation of formic or oxalic acid proceeds, not directly, but by way of a preliminary decarbonylization reaction. However, there is no evolution of gas from CoTAA in a solution of formic acid in dilute sulfuric acid, even at 70 °C. Such a reaction would have to occur on chemical decomposition of formic acid, with evolution of CO and H2O, or CO2 and H2. It may thus be assumed that formic acid is oxidized directly. 

A mixture of 150 parts of oxalic acid, 40 of potassium chlorate, and 20 of water is heated to 60°, and the soln. cone, in vacuo at 50° until it begins to crystallize. The cold liquid i3 then treated with 3 volumes of absolute alcohol, when potassium carbonate is precipitated. Fine deliquescent needles of potassium chlorite can be obtained by fractional crystallization in vacuo. The residue gives a further crop of crystals of the chlorite by treatment with 95 per cent, alcohol. Small yellow crystals of silver or lead chlorites can be obtained by double decomposition. 

K. G. Thurnlackh and K. F. von Hayn prepared a mixed soln. of potassium chlorate and chlorite by the action of potassium hydroxide free from chlorine on a soln. of chlorine dioxide. Light was carefully excluded, and the soln. was evaporated in vacuo at 45°-50°—potassium chlorate separated out first, and after further evaporation, alcohol was added, and the clear alcoholic soln. evaporated. Needle-like crystals of potassium chlorite, KC102, were obtained which deliquesced on exposure to air. As already indicated in connection with the preparation of the acid, G. Bruni and G. Levi made the potassium chlorite by reducing a soln. of potassium chlorate with oxalic acid and A. Reychler, sodium chlorite, by the action of chlorine dioxide on a soln. of sodium peroxide. Sodium chlorite, NaClQ2, can be also made by double decomposition by treating a soln. of barium chlorite with sodium sulphate and evaporating the clear soln. in vacuo. 

The product of nitration of dimethyloxamide is soluble in nitric acid and is separated by pouring the solution into water. It decomposes on treatment with concentrated sulphuric acid or on boiling with aqueous ammonia or barium hydroxide solution, forming the corresponding methylnitramine salt. Similarly, long-continued boiling in water results in complete decomposition, with the formation of oxalic acid and methylnitramine. 

The treatment of cyanates with organic acids (oxalic acid, for example) in a non-aqueous medium, for instance by grinding the two together, does not result in the decomposition of cyanic acid, but in the formation of a trimer, cyamelide, to which the formula of the trioxymethylene derivative is attributed (I)... 

If a powder which decomposes and forms acid products is mixed with a healthy" powder it causes the latter to decompose. The products of decompostion of smokeless powder were found to contain formic add, hydroxypyruvie acid CH2OH- CO COOH, hydroxyisobutyric acid (CH3)2C(OH)COOH and oxalic acid. All these acids except oxalic acid are hygroscopic, hence by increasing the moisture content in the powder, they hasten its decomposition. Acid products react with alkaline stabilizing components. 

Oxidative decomposition of 2//-pyrantetracarboxylic acid 149 with hydrogen peroxide or nitric acid gave traces of succinic and oxalic acids, respectively.194 3-Methyl-4//-thiopyran (3) was reported to be oxidized with potassium permanganate to oxalic and acetic acids.6... 

The formation and decomposition of Crv in aqueous and non-aqueous media during the oxidation of organic substrates such as oxalic acid and ethylene glycol by potassium dichromate has been recognized for some time. No study resulted in the isolation of a stable, well-characterized chromium(V) complex until 1978 when potassium bis(2-hydroxy-2-methylbutyrato)oxochromate(V) monohydrate was prepared from chromium trioxide and the tertiary a-hydroxy acid in dilute perchloric acid according to equation (91). The Crv, which is... 

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