Halogen carboxylic acids

Differences in solubility of the reactants may for example be utilized as follows. Sodium iodide is much more soluble in acetone than are sodium chloride or sodium bromide. Upon treatment of an alkyl chloride or bromide with sodium iodide in acetone, the newly formed sodium chloride or bromide precipitates from the solution and is thus removed from equilibrium. Alkyl iodides can be conveniently prepared in good yields by this route. Alkyl bromides are more reactive as the corresponding chlorides. Of high reactivity are a-halogen ketones, a-halogen carboxylic acids and their derivatives, as well as allyl and benzyl halides. 

The introduction of iodine is carried out according to the methods given on pp. 96, 97. /9-Halogenated carboxylic acids are obtained by the addition of hydrogen halides to aj3-unsaturated acids ... 

Replacement of Halogens by Fluorine in Halogenated Carboxylic Acid... 

C. O. da Silva, E. C. da Silva and M. A. C. Nascimento, Ab initio calculations of absolute pKa values in aqueous solution. II. Aliphatic alcohols, thiols, and halogenated carboxylic acids, J. Phys. Chem. A, 104 (2000) 2402-2409. 

As a reflection of the important role of carboxylic acids in intermediary metabolism, compounds that serve as carboxylic acid mimics or as inhibitors of carboxylic acid processing enzymes have been extremely useful biochemical tools. A host of halogenated carboxylic acids have been synthesized and studied in this regard. Selected examples are given in this section. More extensive reviews are available52,53. 

Molybdenum(VI) fluoride which is a liquid at room temperature (bp 35 C) converts carboxylic acids into trifluoromethyl compounds (Table 7).174- 75 No halogen exchange takes place in halogenated carboxylic acids.174 Benzoic acid could not be fluorinated using this method.174 With trifluoroacclic acid only the acyl fluoride has been obtained. 

Mechanistic studies of the pyrolysis of disodiuni perfluoropentanedioate70 and derivatives71 have shown that the acid fluorides are formed during the reaction. The formation of dienes from the salts of halogenated carboxylic acids with a terminal C = C bond is also possible. The thermal decomposition of sodium (Z)-6//-perlluoro(6-chlorohex-5-enoate) gives (Z)-l//-perfluoro(l-chloropenta-l,4-diene) (7) in 75% yield.72 The decarboxylation of potassium 5H-perfluoropcnt-4-enoate, however, gives 1//-perfluorobut-2-yne (8) via the isomerization of the intermediate butadiene by potassium fluoride.72165... 

A Aliphatic carboxylic acids Aromatic carboxylic acids o Halogenated carboxylic acids... 

A Alphatic carboxylic acids Aromatic carboi lic acids o Halogenated carboxylic acids A A... 

Keene W. C., Eobert J. M., Maben J. R., Scharffe D. H., and Crutzen P. J. (2001) Emissions of volatile inorganic halogens, carboxylic acids, NH3, and SO2 from experimental burns of southern African biofuels. EOS, Trans., AGU 82, Abstract aSlA-0043. 

Ionic halocarbons, including halogenated carboxylic acids, may form pho-toreactive complexes with transition metals in the aquatic environment. Indeed, complexes of carboxylates with dissolved Fe(III) and iron oxides are very photoreactive under solar radiation (28, 29). Photoreactions of such complexes may help to explain the enhanced photoreactivity of chlorinated acetates in natural water samples. 

L-Phenylalanine has been produced continuously from ACA with the help of ACA acylase in an enzyme membrane reactor (EMR) with a space-time-yield of 277 g L 1 d1 83 . With ACL acylase, L-Ieucine was produced at 123-180 g L-1 d 1 in the same reactor set-up1821. The dehydroamino acid substrates can be prepared conveniently, either from 2-halogen carboxylic acid esters1841, or, specifically in the case of ACA, via the acetamidomalonic ester route by reaction with benzyl halogenides[851. 

In the disinfection process of drinking water, besides other chlorinated compounds, halogenated carboxylic acids arise. For quality control of drinking water the determination of these contaminants was established using LC-MS with a preference for ESI (cf 15.3.3.2 ESI, haloacetic acids). An application of APCI-MS for haloacetic acid analysis was reported after CE separation in a non-aqueous medium [303]. 

Chiraldex G-TA Alcohols, polyols, amines, amino alcohols, lactones, halogenated carboxylic acid esters, furans, pyrans, epoxides, amino acids and glicidyl analogs. 

Classification Halogenated carboxylic acid Empirical C2H2CI2O2... 

Any of the feedstock components of unsaturated polyesters may contain flame-retardant element(s). In practice, halogenated carboxylic acids, such as chlorendic acid, or their anhydrides, tetrachloro- or tetrabromophthalic anhydride are more usually introduced as separate components. 

Recently K. E. Moller [600] described the synthesis of halogenated carboxylic acids from halogenated olefins. Thus, methallyl chloride reacted in the presence of BFg-containing catalysts to give monochloropivalic acid in 70 % yield. 

This strategy (for halogenating carboxylic acids) is caUed the Hell-Volhard-Zelinsky reaction. 

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