Oxalic acid catalysis

Teoh, W.Y., R. Amal, L. Madler and S.E. Pratsinis (2007). Flame sprayed visible light-active Fe-Ti02 for photomineralisation of oxalic acid. Catalysis Today, 120(2), 203-213. 

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). ... 

Early work of Dhar established that oxidation of oxalic acid by chromic acid occurs readily, but some of his kinetic data are unreliable as the substrate itself acted as the source of hydrogen ions. The reaction is first-order in oxidant and is subject to strong manganous ion catalysis (as opposed to the customary retardation), the catalysed reaction being zero-order in chromic acid. This observation is related to those found in the manganous-ion catalysed oxidations of several organic compounds discussed at the end of this section. 

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. 

Experimental observations indicate that the oxidation of cobalt (II) to cobalt (III) and the formation of ethylenediamine from N-hydroxyethylethylene-diamine occur simultaneously. This is quite the opposite to what is usually assumed in other instances of transition metal catalysis of organic reactions—for example, the catalytic effect of manganese in the oxidation of oxalic acid (7, 8), of iron in the oxidation of cysteine to cystine (22) and of thioglycolic acid to dithioglycolic acid (5, 23), of copper in the oxidation of pyrocatechol to quinone and in the oxidation of ascorbic acid (29, 30), and of cobalt in the oxidation of aldehydes and unsaturated hydrocarbons (4). In all these reactions the oxidation of the organic molecule occurs by the abstraction of an electron by the oxidized form of the metal ion. 

This sensitivity to substitution of neutral hydrolysis means that the pH-independent reaction gradually becomes more important than the hydroxide reaction at the high pH end of the region, and becomes much more rapidly more important than acid-catalyzed hydrolysis at low pH. Thus from Fig. 13, the acid-catalyzed reaction can be seen to be significant for the hydrolysis of ethyl acetate between pH 4 and 5, and for phenyl acetate about pH 2 but for 2,4-dinitrophenyl acetate the acid-catalyzed reaction is not detectable at pH 1, and is presumably important only in relatively strong acid. It seems certain that this fast neutral hydrolysis is at any rate a partial explanation for the low efficiency of acid catalysis in the hydrolysis of very weakly basic esters, such as the trifluoroacetates and oxalates, in moderately concentrated acid (see p. 145). 

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... 

Quid N, Morgada ME, Piperata G, Babay P, Gettar RT, Litter MI. Oxalic acid destruction at high concentrations by combined heterogeneous photocatalysis and photo-Fenton processes. Catalysis Today 2005 101 253-60. 

Popova GY, Andrushkevich TV, Aleshina GI, Plyasova LM, Khramov MI. Effect of oxalic acid content and medium of thermal treatment on physicochemical and catalytic properties of MoVTeNb oxide catalysts in propane ammoxidation. Applied Catalysis A General. 2007 328(2) 195-200. 

Unlike studies in which acid and base catalysts are distinct molecular species, most attempts to observe bifunctional catalysis when the two catalytic sites are enclosed within the same molecule (whether in the catalyst or in the substrate itself) have failed. First, Lienhard and Anderson (1967) studied acetone iodination catalysed by the monoanions and dianions of a number of dicarboxylic (or polycarboxylic) acids (oxalic acid, 1,1-cyclobutane dicarboxy-lic acid, succinic acid and cis-1,2,3,4-cyclopentanetetracarboxylic acid) for which mechanism (21) can be assumed. It was observed that the catalytic... 

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. 

Mendive, C.B., D.W. Bahnemann and M.A. Blesa (2005). Microscopic characterization of the photocatalytic oxidation of oxalic acid adsorbed onto Ti02 by FTIR-ATR. Catalysis Today, 101(3 1), 237-244. 

The heterogeneous catalysis of gas reactions has been extensively studied and indeed forms the subject matter of three previous volumes (19-21) of Comprehensive Chemical Kinetics. The heterogeneous catalysis of solution ractions has received far less systematic attention. This is surprising since the phenomenon has been known and utilised sporadically for almost 150 years. As long ago as 1845, Millon [1] found that the oxidation of oxalic acid by iodate... 

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... 

Polymerization under acidic conditions, the first control scenario mentioned, employs an initial formaldehyde to phenol ratio of 0.75-0.85 to 1. Stoichiometric ratio would be 1.5 to 1. Catalysis is achieved by using a strong acid 0.1-0.3%, hydrochloric acidiphenol ratio, or 0.5-2% oxalic acid to... 

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

Catalysis of the oxidation of oxalic acid to carbon dioxide by oxygen (air) has been described by Warbnrg [99] and stndied in detail by Rideal and Wright... 

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 ... 

Carbon-11 can also be inserted into an aromatic ring Methyl chloroformate has been converted into carbon-11 labelled oxalic acid in a three-step synthesis. The first step (equation 75) was done in a water-dichloromethane mixture using tetrabutylammonium hydroxide and CN" under phase transfer catalysis conditions. The conversion to the diethyl ester and to the oxalic acid were done in high yields in 0.5 and 0.25 minute, respectively, in a microwave cavity. 

While little is known about the actual rates or equilibria of Cr(V) and Cr(IV) substitution reactions, Hintze and Rocek have been able to show from a study of the oxalic add catalysis of chromic acid oxidation of tris l,10-phenanthrohne)iron(II) that the substitution reactions of Cr(V) and Cr(IV) must be at least an order of magnitude greater than 4 X 10 NT s-. ... 

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