Chlorinated carboxylic acids

Onodera et al. [8] examined the applicability of isotachophoresis to ttie identification and determination of chlorinated mono- and dicarboxylic acids in chlorinated effluents. Four electrol3rte systems for the separation of acids were evaluated. The potential unit values in each system were determined for the chlorinated acids. A mechanism for the reaction of phenol with h)q)ochlorite in dilute aqueous solutions is suggested, based 

Yu and Dovichi [10] used capillary zone electrophoresis with thermo-optical absorbance detection to determine sub pg Lconcentrations of 18 amino acids. 

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The formulated mechanism is supported by the finding that no halogen from the phosphorus trihalide is transferred to the a-carbon of the carboxylic acid. For instance, the reaction of a carboxylic acid with phosphorus tribromide and chlorine yields exclusively an a-chlorinated carboxylic acid. In addition, carboxylic acid derivatives that enolize easily—e.g. acyl halides and anhydrides—do react without a catalyst present. 

Attempts have been made to apply the structure-activity concept (Hansch and Leo 1995) to environmental problems, and this has been successfully applied to the rates of hydrolysis of carbamate pesticides (Wolfe et al. 1978), and of esters of chlorinated carboxylic acids (Paris et al. 1984). This has been extended to correlating rates of biotransformation with the structure of the substrates and has been illustrated with a number of single-stage reactions. Clearly, this approach can be refined with the increased understanding of the structure and function of the relevant degradative enzymes. Some examples illustrate the application of this procedure ... 

Paris DF, NL Wolfe, WC Steen (1984) Microbial transformation of esters of chlorinated carboxylic acids. Appl Environ Microbiol 47 7-11. 

The occurrence of chlorinated organic compounds in fish from polluted waters is rather frequent. ° Chlorinated carboxylic acids of fatty acid character have also been shown to account for up to 90% of the extractable organically bound chloride (EOCl) in fish. Purification by thin layer chromatography of methyl esters of dichlorote-tradecanoic, dichlorohexadecanoic, and dichlorooctadeca-noic acids was used. They were detected at 1200 ppm of EOCl in fish. 

Lindstrdm, K. and F. Osterberg. 1986. Chlorinated carboxylic acids in softwood kraft pulp spent bleach liquors. Environ. Sci. Technol. 20 133-138. 

The conversion of an aliphatic carboxylic acid into the a-bromo- (or a-chloro ) acid by treatment with bromine (or chlorine) in the presence of a catal3rtic amount of phosphorus tribromide (or trichloride) or of red phosphorus is known as the Hell-Volhard-Zelinsky reaction. The procedure probably involves the intermediate formation of the acyl halide, since it is known that halogens react more rapidly with acyl haUdes than with the acids themselves ... 

Section 19 16 Halogenation at the a carbon atom of carboxylic acids can be accom plished by the Hell-Volhard-Zehnsky reaction An acid is treated with chlorine or bromine m the presence of a catalytic quantity of phospho rus or a phosphorus trihalide... 

Thioesters Like chlorine sulfur is a third row element with limited ability to donate a pair of 3p electrons into the carbonyl tt system With an electronegativ ity that IS much less than Cl or O however its destabilizing effect on the carbonyl group IS slight and thioesters he m the middle of the group of carboxylic acid derivatives m respect to reactivity... 

Difluoroacetic acid undergoes reactions typical of a carboxylic acid such as forming an ester when heated with an alcohol and sulfuric acid. Typical esters are methyl difluoroacetate [433-53-4], bp, 85.2°C, and ethyl difluoroacetate [454-31-9], bp, 99.2°C. It can also be photochemicaHy chlorinated to chlorodifluoroacetic acid [76-04-0] or brominated in the presence of iron to bromodifluoroacetic acid [667-27-6] (37,38). 

In the photolysis of difiuorodiazirine (218) a singlet carbene was also observed (65JA758). Reactions of the difiuorocarbene were especially studied with partners which are too reactive to be used in the presence of conventional carbene precursors, such as molecular chlorine and iodine, dinitrogen tetroxide, nitryl chloride, carboxylic acids and sulfonic acids. Thus chlorine, trifiuoroacetic acid and trifiuoromethanesulfonic acid reacted with difiuorodiazirine under the conditions of its photolysis to form compounds (237)-(239) (64JHC233). 

Imidazole-5-carboxamide, l-methyl-4-nitro-mass spectra, 5, 359 Imidazole-4-carboxanilide, 1-methyl-synthesis, 5, 435 Imidazolecarboxylic acid, vinyl-polymers, 1, 281 Imidazole-2-carboxylic acid chlorination, 5, 398 mass spectra, 5, 360 synthesis, 5, 474... 

Isoxanthopterin-6-carboxylic acid chlorination, 3, 296 synthesis, 3, 304 Isoxanthopterins catabolism, 3, 322 chlorination, 3, 296 degradation, 3, 308 occurence, 3, 323 oxidation, 3, 287 8-riboside synthesis, 3, 319 silylation, 3, 297 structure, 3, 264, 273 synthesis, 3, 298 Isoxazole, 3-acetohydroximoyl-synthesis, 6, 409 Isoxazole, 5-acetyl-3-chloro-oxidation, 6, 53... 

Pyrrole-3-carboxylic acid, l-benzoyl-5-bromo-2,4-dimethyl-ethyl ester chlorination, 4, 271... 

Similarly, carboxylic acid and ester groups tend to direct chlorination to the / and v positions, because attack at the a position is electronically disfavored. The polar effect is attributed to the fact that the chlorine atom is an electrophilic species, and the relatively electron-poor carbon atom adjacent to an electron-withdrawing group is avoided. The effect of an electron-withdrawing substituent is to decrease the electron density at the potential radical site. Because the chlorine atom is highly reactive, the reaction would be expected to have a very early transition state, and this electrostatic effect predominates over the stabilizing substituent effect on the intermediate. The substituent effect dominates the kinetic selectivity of the reaction, and the relative stability of the radical intermediate has relatively little influence. 

CjHgONa, which is obtained from ricinine by replacement of the methoxyl group by hydroxyl, chlorine and hydrogen in succession. Ricinidine, on hydrolysis, yields first an amide, C7Hg02N, and then a carboxylic acid, by ... 

PCI5 chlorinates alcohols to alkyl halides and carboxylic acids to the corresponding RCOCl. When heated with NH4CI the phosphonitrilic chlorides are obtained (p. 536). These and other reactions are summarized in the diagram. 

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