Propionic acid, bromination

By-products include propylene dibromide, bis-(bromopropyl) ether, propylene glycol, and propionic acid. Bromide losses are to the brominated organics and bromate formation. Current efficiency is a function of ceU design and losses to bromate. Energy consumption decreases with an increase in electrolyte concentration and a decrease in current density. Space—time yield increases with current density. See Table 5 for performance data (see... 

Propionic acid, 2-bromo-3-(3-indolyl)-methyl ester rearrangement, 4, 279 Propionic acid, 3-(3,4-dimethyoxyphenyl)-dihydrocoumarin synthesis from, 3, 848 Propionic acid, indolyl-synthesis, 4, 232 Propionic acid, 3-(l-indolyl)-sodium salt pyrolysis, 4, 202 Propionic acid, 3-(3-indolyl)-intramolecular acylation, 4, 220, 221 Propionic acid, 3-phenoxy-chroman-4-one synthesis from, 3, 855 Propionic acid, 3-(3-phenylisoxazoI-5-yl)-bromination, 6, 25... 

Rosenau, T. Potthast, A. Kosma, R Habicher, W. D. Novel tocopherol compounds XI. Synthesis bromination and oxidation reactions of 3-(5-tocopheryl)propionic acid. Synlett 1999, 3, 291-294. 

But catalytic reduction of the same phenyl propionic acid gives cis cinnamic acid. Therefore by adding hydrogen under various conditions, one can obtain a desired isomer. The conversion of acetylene into olefinic compounds has been carried out not only for the sake of obtaining the adduct, but Michael studied the various addition reactions for the sake of obtaining a desired product cis or trans. For example, he found that the addition of bromine to acetylene-dicarboxylic acid leads predominantly to the formation of trans isomer. 

Bromination of cinnamic acid with NBS in aq. MeOH gives 2-bromo-3-methoxy-3-phenyl propionic acid, PhCH(0Me)CHBrC02H. At moderately high [H+] the reaction is second-order and independent of [H+], whereas at low [H+] the rate increases with decrease in [H+], Succinimide inhibits the reaction182. 

The second method of preparation (shown in Scheme 2) depends on treating dehydroepiandrosterone (prepared from cholestrol or sitosterol) with acetylene to form the 17a-ethnyl-17p-hydroxy derivative, which is carbonated to the 17a-propionic acid. Reduction of the unsaturated acid in alkaline solution yields the saturated acid, which cyclizes to the lactone on acidification. Bromination to the 5,6-dibromo-compound, followed by oxidation of the hydroxyl group to the ketone, and then dehydro-bromination to the 7a-hydroxyl derivative, produces spironolactone when esterified with thiolacetic acid. 

X-Benzoylindolinyl-3-propionic acid (XXVIII) was condensed to form the tricyclic ketone XXIX via the acid chloride. The bromination... 

From a-a-Di-brom Propionic Acid.—Di-brom propionic acid with both bromine atoms in the alpha position yields pyro-racemic acid by treatment with silver oxide. 

Place 37 g of pure propionic acid in the flask, add 84 g of bromine, and connect with the reflux condenser. Raise the stopper connecting the top of the condenser with the absorption line, add rapidly 1-2 ml of phosphorus trichloride, and replace the stopper securely. Warm the water bath under the flask slowly until the reaction begins (40-50 ). Adjust the flame so that the evolution of hydrogen bromide is not so vigorous as to carry any considerable vapor of bromine into the absorption bottles. The reaction proceeds smoothly without a great deal of watching. When bromine vapor no longer appears in the condenser tube, the reaction is completed. 

Derivation By heating propionic acid with bromine. 

To 50 g. of propionic acid and 7.6 g. of dry amorphous phosphorus are added, drop by drop, 66 7 g. of bromine, at about which point evolution of hydro-bromic add ceases. Through the intermediate formation of phosphorus bromides the acid is converted into the bromide according to the equation (Zelinsky) ... 

Halogenated compounds were detected in higher concentrations in all Rhine water samples investigated. Surprisingly, the halogenated aromatics were highly dominated by brominated compounds comprising brominated phenols, (methoxyphenyl)propionic acids and... 

The first group of contaminants comprises several isomers of mono- and dibrominated (methoxyphenyl)propionic acids. Their occurrence and isomeric distribution is illustrated in Fig. 2. All position isomers with respect to the methoxy group were present. However, for each methoxy substitution (2-, 3- and 4-substitution) only one isomer considering the bromination position was observed in most cases. Just one further monobrominated isomer was detected in the water samples which was not attributed to synthesized reference material. With respect to its mass spectral properties (as discussed above) the occurrence of a further 3-(bromo-2-methoxyphenyl)propionic acid methylester is likely. Interestingly, a very similar isomer pattern of reference substances was obtained by nonselective bromination of the corresponding nonhalogenated compounds (see also Fig. 5). Therefore, a technical preparation of these contaminants can be suggested. 

Fig. 3 Mass spectra of brominated 3-(methoxyphenyl)propionic acid methylesters identified in Rhine water samples.

In Fig. 5 the synthetic pathway as well as the IR spectroscopic properties of one reference substance, 3-(bromo-4-methoxyphenyl)propionic acid methylester, are presented. However, it has to be noted that also IR spectroscopic analyses are not suitable for the determination of the bromine substitution position. 

Additionally, several brominated compounds were identified for the first time as environmental contaminants. Their analytical properties (mass spectral, gas chromatographic and IR spectroscopical data) revealed the occurrence of mono- and dibrominated (methoxyphenyl)propionic acids and hydroxymethylacetophenones. Interestingly, the Rhine water samples investigated were dominated by brominated compounds as compared to chlorinated substances. This is an unusual state of riverine pollution with respect to halogenated compounds. 

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