Propionic acid, 3- oxidation

Disposition in the Body. Rapidly and almost completely absorbed after oral administration. Metabolised by reduction to 2-(5-a-hydroxybenzyl-2-thienyl)propionic acid, oxidation to 2-(5-p-hydroxybenzoyl-2-thienyl)propionic acid, and conjugation with glucuronic acid. About 60% of an oral dose is excreted in the urine in 24 hours, about 55% as tiaprofenic acid (excreted mainly as an acylglucuronide conjugate), and about 5% as the two metabolites, excreted partly as acylglucuronides. 

As was already pointed out, methylmalonic aciduria occurs in children as a hereditary disease. Some patients are responsive to large doses of vitamin Bi2-The biochemical pathogenesis of the disease has been clarified at least in part. Cultures of fibroblasts obtained from such patients oxidize propionate and methylmalonic acid to CO2 much more slowly than do fibroblasts obtained from normal cells. But if large amounts of hydroxycobalamin are added to the culture medium, methylmalonate and propionic acid oxidation is restored to normal, thus excluding a defect in the methylmalonate mutase levels. Assays for deoxyadenosylcobalamin in fibroblasts obtained from methylmalonic aciduria patients and normal individuals revealed that the concentration of coenzyme is in the mutant only 10% of that in the normal fibroblast. Inasmuch as the mechanism of vitamin B12 conversion to the deoxyadenosylcobalamin coenzyme is not known, except for the fact that several enzymic steps are involved, the exact nature of the defect in methylmalonic aciduria cannot be ascertained. 

Butane-Naphtha Catalytic Liquid-Phase Oxidation. Direct Hquid-phase oxidation ofbutane and/or naphtha [8030-30-6] was once the most favored worldwide route to acetic acid because of the low cost of these hydrocarbons. Butane [106-97-8] in the presence of metallic ions, eg, cobalt, chromium, or manganese, undergoes simple air oxidation in acetic acid solvent (48). The peroxidic intermediates are decomposed by high temperature, by mechanical agitation, and by action of the metallic catalysts, to form acetic acid and a comparatively small suite of other compounds (49). Ethyl acetate and butanone are produced, and the process can be altered to provide larger quantities of these valuable materials. Ethanol is thought to be an important intermediate (50) acetone forms through a minor pathway from isobutane present in the hydrocarbon feed. Formic acid, propionic acid, and minor quantities of butyric acid are also formed. 

Anhydrous Acetic Acid. In the manufacture of acetic acid by direct oxidation of a petroleum-based feedstock, solvent extraction has been used to separate acetic acid [64-19-7] from the aqueous reaction Hquor containing significant quantities of formic and propionic acids. Isoamyl acetate [123-92-2] is used as solvent to extract nearly all the acetic acid, and some water, from the aqueous feed (236). The extract is then dehydrated by azeotropic distillation using isoamyl acetate as water entrainer (see DISTILLATION, AZEOTROPIC AND EXTRACTIVE). It is claimed that the extraction step in this process affords substantial savings in plant capital investment and operating cost (see Acetic acid and derivatives). A detailed description of various extraction processes is available (237). 

Other possible chemical synthesis routes for lactic acid include base-cataly2ed degradation of sugars oxidation of propylene glycol reaction of acetaldehyde, carbon monoxide, and water at elevated temperatures and pressures hydrolysis of chloropropionic acid (prepared by chlorination of propionic acid) nitric acid oxidation of propylene etc. None of these routes has led to a technically and economically viable process (6). 

Only with propanal are very high conversions (99%) and selectivity (> 98 0) to MMA and MAA possible at this time. Although nearly 95% selective, the highest reported conversions with propionic acid or methyl propionate are only 30—40%. This results in large recycle streams and added production costs. The propanal route suffers from the added expense of the additional step required to oxidize methacrolein to methacrylic acid. 

Activators. Activators are chemicals that increase the rate of vulcanization by reacting first with the accelerators to form mbber soluble complexes. These complexes then react with the sulfur to achieve vulcanization. The most common activators are combinations of zinc oxide and stearic acid. Other metal oxides have been used for specific purposes, ie, lead, cadmium, etc, and other fatty acids used include lauric, oleic, and propionic acids. Soluble zinc salts of fatty acid such as zinc 2-ethyIhexanoate are also used, and these mbber-soluble activators are effective in natural mbber to produce low set, low creep compounds used in load-bearing appHcations. Weak amines and amino alcohols have also been used as activators in combination with the metal oxides. 

With the exception of acetic, acryUc, and benzoic all other acids in Table 1 are primarily produced using oxo chemistry (see Oxo process). Propionic acid is made by the Hquid-phase oxidation of propionaldehyde, which in turn is made by appHcation of the oxo synthesis to ethylene. Propionic acid can also be made by oxidation of propane or by hydrocarboxylation of ethylene with CO and presence of a rhodium (2) or iridium (3) catalyst. 

Chloro-2,2,3-trifluoropropionic acid has been prepared by permanganate oxidation of 3-chloro-2,2,3-trifluoropropanol which is one of the telomerization products of chlorotrifluoroethylene with methanol. The present procedure is a modification of one reported earlier and is undoubtedly the method of choice for making propionic acids containing 2 fluorine atoms, i.e., 2,2,3,3-tetrafluoropropionic acid, 3,3-dichloro-2,2-difluoropropionic acid, and 3-bromo-2,2,3-trifluoropropionic acid. When preparing 2,2,3,3-tetrafluoropropionic acid from tetrafluoroethylene, it is desirable to use an additional 50 ml. of acetonitrile and externally applied heat to initiate the reaction. 

Succinyl-CoA derived from propionyl-CoA can enter the TCA cycle. Oxidation of succinate to oxaloacetate provides a substrate for glucose synthesis. Thus, although the acetate units produced in /3-oxidation cannot be utilized in glu-coneogenesis by animals, the occasional propionate produced from oxidation of odd-carbon fatty acids can be used for sugar synthesis. Alternatively, succinate introduced to the TCA cycle from odd-carbon fatty acid oxidation may be oxidized to COg. However, all of the 4-carbon intermediates in the TCA cycle are regenerated in the cycle and thus should be viewed as catalytic species. Net consumption of succinyl-CoA thus does not occur directly in the TCA cycle. Rather, the succinyl-CoA generated from /3-oxidation of odd-carbon fatty acids must be converted to pyruvate and then to acetyl-CoA (which is completely oxidized in the TCA cycle). To follow this latter route, succinyl-CoA entering the TCA cycle must be first converted to malate in the usual way, and then transported from the mitochondrial matrix to the cytosol, where it is oxida-... 

There is a compound called propanol with structural formula CH3CH2CH2OH. If it is oxidized carefully, an aldehyde called propionaldehyde is obtained. Vigorous oxidation gives an acid called propionic acid. Draw structural formulas like those shown in Figures 18-6 and 18-7 for propionaldehyde and propionic acid. 

Balance the half-reaction involved in the oxidation of ethanol to acetic acid. Compare the number of electrons released per mole of ethanol with the number per mole of methanol in the equivalent reaction (73c). How many electrons would be released per mole of propanol in the oxidation to propionic acid ... 

Parallel ketonization of acetic acid and propionic acid was one of the transformations of this type studied in our Laboratory. Ryba6ek and Setinek (94) investigated the kinetics of these reactions in the gaseous phase at 316°C using thorium oxide on activated carbon (p. 27) as the catalyst. This model system allowed the study of each reaction separately as well as of the simultaneous conversion of both acids. 

When one of the two acids is used in excess and the pk -values of the two acids differ strongly, the salt deficit method should be used with caution. Formic add, acetic acid, propionic acid, and trifluoroacetic acid have been electrolyzed competitively in mixtures of pairs. Formic acid and trifluoroacetic acid are comparable in case of electrolysis, both are more readily electrolyzed than acetic and propionic adds. Deviations are rationalized on the basis of differences in ionization [147]. It might 1 useful in such cases to neutralize both acids completely. Sometimes one of the two acids, although being the minor component, is more favorably oxidized possibly due to preferential adsorption or its higher acidity [148]. In this case the continuous addition of the more acidic add to an excess of the weaker acid may lead to successful cross-coupling [149], The chain length of the two acids should be chosen in such a... 

The kinetics of oxidation of propionic acid in aqueous perchloric acid by Co(III) perchlorate are ... 

Esterification of the propionic acid side chain at C-13 (ring C) with a methyl group catalyzed by S-adenosyl-L-methionine-magnesium protoporphyrin 0-meth-yltransferase yields protoporphyrin IX monomethyl ester (MPE), which originates protochlorophyllide by a P-oxidation and cyclization of the methylated propionic side chain. This molecule contains a fifth isocyclic ring (ring E), the cyclopentanone ring that characterizes aU chlorophylls. 

To obtain a better understanding of the reaction mechanism, some compounds that are considered to he intermediates were subjected to the reaction. Various reaction courses can be considered as illustrated in Fig. 21. Path A a-Methyltropic acid is oxidized to a-phenyl-a-methylmalonic acid. Then, the malonate is converted to optically active a-phenylpropionate hy arylmalonate decarboxylase. In order to confirm this assumption, incubation of the malonic acid with Rhodococcus sp. was carried out. The result obtained was the total recovery of the substrate, indicating that no decarboxylase is present in this bacterium. Path B a-Methyltropic acid is converted to racemic a-phenylpropionic acid, which is deracemized to optically active propionic acid. To examine the possibility of this route, racemic a-phenylpropionic acid was subjected to the reaction to observe... 

While tocopherylacetic aicd (51), the lower Crhomologue of 3-(5-tocopheryl)-propionic acid (50) showed a changed redox behavior (see Section 6.5.1), compound 50 displayed the usual redox behavior of tocopherol derivatives, that is, formation of both ortho- and para-quinoid oxidation intermediates and products depending on the respective reaction conditions. Evidently, the electronic substituent effects that... 

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