Trichloroacetic acid , decomposition

Trichloroacetic acid K = 0.2159) is as strong an acid as hydrochloric acid. Esters and amides are readily formed. Trichloroacetic acid undergoes decarboxylation when heated with caustic or amines to yield chloroform. The decomposition of trichloroacetic acid in acetone with a variety of aUphatic and aromatic amines has been studied (37). As with dichloroacetic acid, trichloroacetic acid can be converted to chloroacetic acid by the action of hydrogen and palladium on carbon (17). 

Stabilized tetrachloroethylene, as provided commercially, can be used in the presence of air, water, and light, in contact with common materials of constmction, at temperatures up to about 140°C. It resists hydrolysis at temperatures up to 150°C (2). However, the unstabilized compound, in the presence of water for prolonged periods, slowly hydrolyzes to yield trichloroacetic acid [76-03-9] and hydrochloric acid. In the absence of catalysts, air, or moisture, tetrachloroethylene is stable to about 500°C. Although it does not have a flash point or form flammable mixtures in air or oxygen, thermal decomposition results in the formation of hydrogen chloride and phosgene [75-44-5] (3). 

Similarly, a-trichloromethylamines (522) were obtained by decomposition of trichloroacetic acid in morpholine enamines, but an amide ester was formed from sodium trichloroacetate and the imonium salt of pyrrolidino-cyclohexene (523). The product is presumably derived from opening of an intermediate dichloroaziridinium salt. 

The products of the thermal decomposition of 1,10-phenanthroline have been briefly discussed.370 Exchange of hydrogen for deuterium has been noted with alkali metal complexes of 1,10-phenanthroline. The exchange occurs principally in the 5-position.371,372 A new chemiluminescence reaction arising from the combination of trichloroacetic acid and 4,7-diphenyl-l,10-phenanthroline has been reported.373... 

Jensen et al.16 also studied the decomposition of 5-ethoxythiatriazole in dibutyl phthalate solution in the presence of trichloroacetic acid, tripentylamine, 4-benzylpyridine, anhydrous aluminum chloride, or trinitrobenzene, but practically no effect on the reaction rate was observed. However, later experiments have shown that the decomposition can indeed by enhanced catalytically by Lewis acids under conditions where the catalyst is not sequestered by complex formation with the solvent.19 Thus the addition of aluminum chloride to 5-phenylthiatriazole in benzene causes a brisk evolution of nitrogen at room temperature, and if instead boron tribromide is added, a rather violent reaction sets in. However, when esters or ethers are used as... 

Sodium trichloroacetate may be purchased from the Dow Chemical Company (96.4% pure by Cl analysis) or prepared by neutralizing trichloroacetic acid (Matheson Coleman and Bell) with aqueous sodium hydroxide to the phenolphthalein end point. The product is dried under vacuum for 12 hours, sieved, then dried an additional 12 hours under vacuum, all at room temperature. The salt prepared by this method and used in this preparation was 98.5% pure, based on chlorine analysis, and can be stored indefinitely without decomposition. The submitter has obtained nearly identical yields of phenyltrichloromethyl-mercury from the commercial and from the prepared salts. 

Trichloroacetic acid decomposes in certain solvents in the neighborhood of 100° to give chloroform and carbon dioxide. A much higher temperature is required for decomposition in the gas phase and then a different set of products is obtained. The reaction is interesting because it illustrates15 how in at least one case the solvent effect and a whole mass of complex data can be nicely interpreted. 

It will be noted that the energy of activation is greatest in water, next in alcohol, and least in aniline, and it is probable that water tends to solvate more than alcohol, and alcohol to solvate more than aniline. These actual differences in the energies of activation can be attributed to heats of solvation which must be added to the energy of activation before decomposition can occur. The products chloroform and carbon dioxide are not solvated. It will be remembered that the trichloroacetic acid itself is completely stable, as shown by the failure to decompose in such solvents as carbon tetrachloride and sulphuric acid. This stabilizing of the trichloroacetate ion by the proton may be considered as a special limiting case towards which the stabilization by solvation can approach. 

Table 59 presents activation parameters for the decarboxylation of trichloroacetic acid in various basic solvents. Presumably the acid is in the form of its anion in these solvents. The activation parameters fall into a fairly narrow range and the differences presumably represent specific solvation effects. In an acidic solvent, decanoic acid, the activation parameters for the decomposition of potassium trichloroacetate are increased considerably. The values are A/f = 41.4 kcal.mole" and A5 = 27.7 eu . The activation parameters presumably reflect a composite of a prior equilibrium between decanoic acid and the trichloroacetate anion along with decarboxylation of the latter anion. The rate of decarboxylation of sodium nitroacetate is about five times faster in methanol than in water . This effect was attributed to dispersion of the negative charge at the transition state , a process which is more favorable in the less polar methanol solvent. Similarly, the decar-... 

The triazene 6, also derived from anthranilic acid, is more stable than 4 and can safely be stored in quantity. Benzyne, carbon dioxide, and dimethylamine are formed by decomposition of 6 in chlorobenzene at reflux temperature, or in benzene at 80°C in the presence of trichloroacetic acid.13 Benzyne is also produced on pyrolysis of diphenyliodonium-2-carboxylate (7) in various solvents at 160-220°C.14... 

The sodium salt of trichloroacetic acid is obtained from the acid by neutralisation with sodium hydroxide. To avoid the decomposition just described, neutralisation is carried out at low temperatiue. 

Prepared from chloral and urea by condensation catalysed with HCl, it is a crystalline compound insoluble in water and stable to acids. In alkaline medium it is decomposed into dichloroacetic acid and urea. In the soil it yields trichloroacetic acid by oxidative decomposition. According to Melnikov (1971a) these reactions... 

It is seen in the case of the jS-halogen-substituted acids, that an analogous decomposition takes place in water solution at or below the boiling point. Other acids which contain groups more negative than the alkyl radicals undergo a similar decomposition very readily. For example, when trichloroacetic acid is boiled with water, chloroform is formed —... 

C-doped Ti02 was also prepared through the following processes controlled oxidative annealing of titanium carbide (TiC) for decomposition of trichloroacetic acid under visible light irradiation... 

Slow Reactions When investigating a slow reaction, a small sample of the reacting mixture can be taken to instantly determine the concentration of the reaction partners chemically by, for example, titration or gravimetry. This is called real-time analysis. As an example, we wiU investigate the decomposition of trichloroacetic acid by decarboxylation into chloroform according to... 

Abbreviations alk. alkaloids (cyclopenin + cyclopenol) CH cycloheximide dpm decompositions per minute, cf. 2. P cyclopium Penicillium cyclopium p. i. after inocu-lation of cultures prot. TOA-insoluble fraction of homogenate (protein) TCA trichloroacetic acid L-Phe L-phenylalanine for brevity labelled L Phe stands for radioactively labelled phenylalanine (U- C-L-Phe) and cold L-Phe stands for unlabelled phenylalanine. 

In the presence of trichloroacetic acid the crude, explosive diazonium carboxylate (338) could be isolated in up to 60% yield from the aprotic diazotization of the amino acid (339). Decomposition of 338 in the presence... 

If organic compounds containing halogen are heated with a mixture of potassium permanganate and concentrated sulfuric acid, oxidative decomposition occurs with production of free halogen. The latter. Like other strong oxidants, converts diphenylamine dissolved in concentrated sulfuric acid into a blue quinoidal compound. If, however, a saturated solution of diphenylamine in ethyl acetate that contains some trichloroacetic acid is used, only chlorine yields a blue coloration. Bromine and iodine produce a yellow color that can be discharged by means of sodium thiosulfate. 

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