Oxalic acid, catalysis with

DISN adds to 2,2-dimethoxypropane in the presence of sulfuric acid as catalyst to give 2,2-dimethyl-4,5-dicyanoisoimidazole (9) in 80% yield. Reaction of (I) under oxalic acid catalysis also gives (9) in 80% yield. Reaction with acetone itself gives (9) in low... 

The mechanism of reaction (Scheme 5) involves the proton equilibrium of vanadium(v), followed by reaction with the hydrated form of the a-keto-acid. The values K=3A (35 °C) and 2.0 (30 °C) have been derived kinetically. Initial oxidation of glyoxylic acid to oxalic acid is ruled out in view of the complex reaction of the latter with V. A study has been made, however, of the oxalic acid catalysis of the oxidation of iodide by vanadium(v). ... 

Multiple products are possible from C02 hydrogenation, but all of the products are entropically disfavored compared to C02 and H2 (Scheme 17.1). As a result, the reactions must be driven by enthalpy, which explains why formic acid is usually prepared in the presence of a base or another reagent with which formic acid has an exothermic reaction. Of the many reduction products that are theoretically possible, including formic acid, formates, formamides, oxalic acid, methanol, CO, and methane, only formic acid and its derivatives are readily prepared by homogeneous catalysis. 

Diisopropenyl oxalate results from the addition of oxalic acid to propyne. The ester condenses with all types of amines under ruthenium catalysis to yield the corresponding ester amides or oxamides, depending on the amounts of amines used (equation 104)327. 

Catalytic decarboxylation processes occur in aliphatic keto acids in which the keto group is in an a-position to one carboxyl group and in a P-relationship to another. Thus, the normal decarboxylation of a p-keto acid is facilitated by metal coordination to the a-keto acid moiety. The most-studied example is oxaloacetic acid and it has been shown that its decarboxylation is catalyzed by many metals following the general order Ca2+ < Mn2+ < Co2+ < Zn2+ < Ni2+ < Cu2+ < Fe3+ < Al3"1".66 67 The overall rate constants can be correlated with the stability constants of 1 1 complexes of oxalic acid rather than oxaloacetic acid, as the uncoordinated carboxylate anion is essential for the decarboxylation. The generally accepted mechanism is shown in Scheme 15. Catalysis can be increased by the introduction of x-bonding ligands, which not only increase the... 

Iliev, V., D. Tomova, L. Bilyarska, A. Eliyas and L. Petrov (2006). Photocatalytic properties of Ti02 modified with platinum and silver nanoparticles in the degradation of oxalic acid in aqueous solution. Applied Catalysis B-Environmental, 63(3 4), 266-271. 

It is of some interest to note that Taube in 1948 determined a value of 1.7 V for the Br2 /2Br couple by a careful analysis of the catalysis by Mn2+ of the reaction of Br2 with oxalic acid (308). He also derived a value of 104 M 1 for the equilibrium constant of reaction (18). In his analysis Taube used a potential of 1.6 V for the Mn3+/Mn2+ couple. A value of 1.5 V for the Mn3+/Mn2+ couple is presently recommended in Standard Potentials-, if Taube s data are corrected to this new Mn3+/Mn2+ potential, a potential of 1.6 V is derived for the Br2 /2Br couple, which is essentially the same as the most accurate determinations discussed above. Unfortunately, Taube s contribution seems... 

Novolaks are condensation products of formaldehyde with phenols, obtained by acidic catalysis (usually oxalic acid [27]) ... 

Novolac resins are produced commercially from cresol mixtures that contain amounts of m-cresol and p-cresol isomers in varying proportions, depending on the specific application. The reaction proceeds with both metal cation and acid catalysis (Scheme 1.1) Because of strict guidelines for metallic contaminants in semiconductor grade process materials and chemicals, acid catalysis is employed in the synthesis of novolacs used in photoresist applications. In a typical commercial production process, a mixture of m- and p-cresol isomers, formaldehyde (most often in the form of formalin, a 35-40% aqueous solution of formaldehyde) and an oxalic acid catalyst are reacted, following the description of Pampalone ... 

The utility of bifunctional reagents such as oxalic acid monohydrazide for the resolution of racemic carbonyl compounds has been reported. Glyoxal reacts with ethyl carbamate under acid catalysis to give 1,1,2,2-tetra-(ethoxycarbonylamino)ethane (46) and not, as previously reported, glyoxal bis(ethoxycarbonylimide) (47). 

Many reactions catalyzed by the addition of simple metal ions involve chelation of the metal. The familiar autocatalysis of the oxidation of oxalate by permanganate results from the chelation of the oxalate and Mn (III) from the permanganate. Oxidation of ascorbic acid [50-81-7] C HgO, is catalyzed by copper (12). The stabilization of preparations containing ascorbic acid by the addition of a chelant appears to be negative catalysis of the oxidation but results from the sequestration of the copper. Many such inhibitions are the result of sequestration. Catalysis by chelation of metal ions with a reactant is usually accomphshed by polarization of the molecule, faciUtation of electron transfer by the metal, or orientation of reactants. 

Crotonic esters (unsubstituted or y-substituted) condense with oxalic esters under base catalysis giving 5-oxopentenoic esters 30. In acid, they cyclize to 277-pyran-2-one-6-carboxylic esters 31 which, on ester hydrolysis followed by decarboxylation, provide 2//-pyran-2-ones 32 ... 

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