Carboxylic acids oxalic acid

Simple organic molecules such as small carboxylic acids (oxalate, acetate, malonate, citrate, etc.), amino acids and phenols are all ligands for metals. Such compounds may all occur as degradation products of organic matter in natural waters. The complexes formed are typically charged hydrophilic complexes. The stability of the metal complexes with these ligands is, however, moderate in most cases. Model calculations including such compounds at realistic concentrations indicate that their effects on speciation are relatively small [29],... 

From Hexa-chlor Ethane.—It may also be prepared by oxidizing a derivative of ethane, viz., hexa-chlor ethane, CCle, with potassium hydroxide. This reaction may be considered as yielding the complete oxidation product of ethane by the replacement of the six chlorine atoms by six hydroxyl groups. This then loses water, as in the case of all compounds which contain more than one hydroxyl group linked to one carbon atom, and di-carboxyl, or oxalic acid results, as follows. 

Different organic compounds have been investigated at BDD and BDD/Ir02 electrodes by cyclic voltammetry and preparative electrolysis. As model organic compounds, simple alcohols (methanol, ethanol, n-propanol, isopropanol, and ter-butanol) and simple carboxylic acids (formic acid, oxalic acid, and maleic acid) have been investigated. Two mechanisms can be distinguished for the organics oxidation ... 

R. Tacke, O. Dannappel, M. Muhleisen, Syntheses, Structures, and Properties of Molecular Si-Silicates Containing Bidentate 1,2-Diolato(2-) Ligands Derived from a-Hydroxy-carboxylic Acids, Acetohydroximic Acid, and Oxalic Acid New Results in the Chemistry of Pentacoordinate Silicon", in Organosilicon Chemistry II From Molecules to Materials (Eds. N. Auner, J. Weis), VCH, Weinheim, 1996, pp. All-446. 

A) CARBOXYLIC ACIDS. Formic, acetic, oxalic, succinic,... 

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]. 

Bromophenol blue (3.0...4.6) aliphatic carboxylic acids [225 — 228] malonic and lactic acids [229] palmitic and lactic acids [230] malonic, glycolic, malic, citric, tartaric, ketoglutaric, galacturonic and oxalic acids [196] dicarboxylic acids, succinic acid [231] indoleacetic acid, trichloroacetic acid [232] palmitic acid, palmityl- and stearyllactic acid [223] benzoic, sorbic and salicylic acid [234] metabolites of ascorbic acid [235] chloropropionic acid [236] oligogalacturonic acids [237] amino acids, hydrocarbons, mono-, di- and triglycerides [238] xylobiose, xylose, glucose and derivatives [239] sugar alcohols [91] toxaphene [240]... 

The reactivity of the methylene group adjacent to the lactam group affords the possibility of a Claisen condensation. Thus, treatment of 2-pyrrolidone or 2-piperidone with ethyl oxalate leads to the J -pyrroline-carboxylic (70) and, d -piperideine-2-carboxylic acids (71), respectively. N-methyl lactams furnish N-methyl derivatives (72,73) (Scheme 3). 

The Reissert procedure involves base-catalyzed condensation of an o-nitrotoluene derivative 1 with an ethyl oxalate (2) which is followed by reductive cyclization to an indole-2-carboxylic acid derivative 4, as illustrated below . ... 

In 1897, Reissert reported the synthesis of a variety of substituted indoles from o-nitrotoluene derivatives. Condensation of o-nitrotoluene (5) with diethyl oxalate (2) in the presense of sodium ethoxide afforded ethyl o-nitrophenylpyruvate (6). After hydrolysis of the ester, the free acid, o-nitrophenylpyruvic acid (7), was reduced with zinc in acetic acid to the intermediate, o-aminophenylpyruvic acid (8), which underwent cyclization with loss of water under the conditions of reduction to furnish the indole-2-carboxylic acid (9). When the indole-2-carboxylic acid (9) was heated above its melting point, carbon dioxide was evolved with concomitant formation of the indole (10). 

Under basic conditions, the o-nitrotoluene (5) undergoes condensation with ethyl oxalate (2) to provide the a-ketoester 6. After hydrolysis of the ester functional group, the nitro moiety in 7 is then reduced to an amino function, which reacts with the carbonyl group to provide the cyclized intermediate 13. Aromatization of 13 by loss of water gives the indole-2-carboxylic acid (9). 

Dicarboxylic acids have two dissociation constants, one for the initial dissociation i into a monoanion and one for the second dissociation into a dianion, i-or oxalic acid, H02C—COoH, the first ionization constant has p/Cal = 1.2 and the second ionization constant has pKa2 = 4.2. Why is the second carboxyl group so much less acidic than the first ... 

Habid and Malek49 who studied the activity of metal derivatives in the catalyzed esterification of aromatic carboxylic acids with aliphatic glycols found a reaction order of 0.5 relative to the catalyst for Ti(OBu)4, tin(II) oxalate and lead(II) oxide. As we have already mentioned in connection with other examples, it appears that the activation enthalpies of the esterifications carried out in the presence of Ti, Sn and Pb derivatives are very close to those reported by Hartman et al.207,208 for the acid-catalyzed esterification of benzoic and substituted benzoic acids with cyclohexanol. These enthalpies also approach those reported by Matsuzaki and Mitani268 for the esterification of benzoic acids with 1,2-ethanediol in the absence of a catalyst. On the other hand, when activation entropies are considered, a difference exists between the esterification of benzoic acid with 1,2-ethanediol catalyzed by Ti, Sn and Pb derivatives and the non-catalyzed reaction268. Thus, activation enthalpies are nearly the same for metal ion-catalyzed and non-catalyzed reactions whereas the activation entropy of the metal ion-catalyzed reaction is much lower than that of the non-catalyzed reaction. 

H2CO3 (carbonic acid) aqueous phase HC2H3O2 (acetic acid) aqueous, gas phases HCHOz (formic acid) aqueous, gas phases H2C2O4 (oxalic acid) aerosol particles solid phase RCCX3H (many carboxylic acids)... 

Naturally we shall need to esterify all the carboxylic acid groupings and we then have an unambiguous condensation between enolisable ester (53) and unenolis-able but more electrophilic (a-diCO) diethyl oxalate (54). Hydrolysis of the esters in (55) and cyclisation occur under the same conditions. 

Vegetables also contain carboxylic acids that contribute to their flavors. One example is oxalic acid, prevalent in spinach and rhubarb. Raw rhubarb leaves are mildly poisonous, and folklore holds that the toxic substance is oxalic acid. However, raw spinach can be eaten safely despite its equally high content of this acid. 

C17-0116. Oxalic acid, a diprotic carboxylic acid found in many plants, including rhubarb, is an effective stain remover. Consider the following diagram to be a small section of an aqueous solution of oxalic acid ... 

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