Oxidative isobutyric acid

Isobutyric acid, dimethylacetic acid, 2-methylpropanoic acid, (CHjjjCH COOH, colourless syrupy liquid with an unpleasant odour b.p. 154°C. Prepared by oxidation of 2-methylpropanol with K2Cr207 and H2SO4. Salts soluble in water. Used in alkaline solution for sweetening gasoline. 

Dehydrogenation of Propionates. Oxidative dehydrogenation of propionates to acrylates employing vapor-phase reactions at high temperatures (400—700°C) and short contact times is possible. Although selective catalysts for the oxidative dehydrogenation of isobutyric acid to methacrylic acid have been developed in recent years (see Methacrylic ACID AND DERIVATIVES) and a route to methacrylic acid from propylene to isobutyric acid is under pilot-plant development in Europe, this route to acrylates is not presentiy of commercial interest because of the combination of low selectivity, high raw material costs, and purification difficulties. 

Propylene-Based Routes. The strong acid-catalyzed carbonylation of propylene [115-07-1] to isobutyric acid (Koch reaction) followed by oxidative dehydration to methacrylic acid has been extensively studied since the 1960s. The principal side reaction in the Koch reaction is the formation of oligomers of propylene. Increasing yields of methacrylic acid in the oxydehydration step is the current focus of research. Isobutyric acid may also be obtained via the oxidation of isobutyraldehyde, which is available from the hydroformylation of propylene. The -butyraldehyde isomer that is formed in the hydroformylation must be separated. 

The oxidative dehydration of isobutyric acid [79-31-2] to methacrylic acid is most often carried out over iron—phosphoms or molybdenum—phosphoms based catalysts similar to those used in the oxidation of methacrolein to methacrylic acid. Conversions in excess of 95% and selectivity to methacrylic acid of 75—85% have been attained, resulting in single-pass yields of nearly 80%. The use of cesium-, copper-, and vanadium-doped catalysts are reported to be beneficial (96), as is the use of cesium in conjunction with quinoline (97). Generally the iron—phosphoms catalysts require temperatures in the vicinity of 400°C, in contrast to the molybdenum-based catalysts that exhibit comparable reactivity at 300°C (98). 

Thus, -butyl [71-36-3] [71-36-3] and isobutyl alcohol [78-83-1] [78-83-1] are obtained by hydrogenation of their respective aldehydes and butyric and isobutyric acid are produced by oxidation. 

Catalytic oxidation of isobutyraldehyde with air at 30—50°C gives isobutyric acid [79-31-2] ia 95% yield (5). Certain enzymes, such as horseradish peroxidase, cataly2e the reaction of isobutyraldehyde with molecular oxygen to form triplet-state acetone and formic acid with simultaneous chemiluminescence (6). 

Isobutyric acid, the simple oxidation product of isobutyraldehyde, is employed in the esterification of TMPD to form the mono- and diesters of TMPD. Some isobutyric acid is also used in the production of isobutyronittile, an organo-phosphate pesticide precursor. 

Butyric acid is made by air-oxidation of butyraldehyde, which is obtained by appHcation of the oxo synthesis to propylene. Isobutyric acid is made from isobutyraldehyde, a significant product in the synthesis of butyraldehyde (see Butyraldehydes). Butyraldehyde is also used to make 2-ethylhexanoic acid. 

Kemp and Waters found a primary kinetic isotope effect of 8.7 for oxidation of C-deuterated mandelic acid and noted a large difference in rate between the oxidations of mandelic acid k at 24.4 °C = 1.7 l.mole . sec ) and a-hydroxy-isobutyric acid ( 2 at 24.4 °C = 5.6 x 10 l.mole . sec ) — a difference not reproduced for the oxidation of these compounds by the one-equivalent reagent, manganic sulphate. The various data are fully in accord with a Westheimer-type mechanism, viz. 

Complementary to the work with aqueous acidic media is the study of the homolytic decompositions of Co(III) carboxylates in carboxylic acid media by Lande and Kochi . For example, Co(III) is reduced in pivalic acid media with first-order kinetics with E = 30.6 kcal.mole , AS = 8 eu and k ko = 1.28+0.10 (69 °C). The main oxidation products were found to be isobutylene and tert-butyl pivalate, which suggests that (CH3)3C- is an intermediate. Oxidative decarboxylation is the probable course in the analogous oxidations of n-butyric and isobutyric acids, in view of the production of propane and CO2 under normal... 

The enoHsation may be rate-determining (to afford the zero-order dependence on oxidant concentration) or the oxidation step may be slower (to give the first-order dependence). The second-order dependence on oxidant concentration for acetone and nitroethane cannot involve slow oxidation of a free radical and no ready alternative explanation is available. Maltz showed that the rate of oxidation of isobutanal equals the rate of enolisation, and that two main paths of oxidation are followed subsequent to enolisation leading either to tetramethyldihydropyrazine and a poly-aquocyanoiron(II) species or to isobutyric acid. 

S )-3-nydroxy-2-mcthylpropanoic acid, 13-A, can be obtained in enantiomeri-cally pure form from isobutyric acid by a microbiological oxidation. The aldehyde 13-B is available from a natural product, pulegone, also in enantiomerically pure form. Devise a synthesis of enantiomerically pure 13-C, a compound of interest as a starting material for the synthesis of a-tocopherol (vitamin E). 

Irradiation of diisopropyl ketone under oxygen in the presence of the hindered piperidine II likewise results in formation of isobutyric acid, acetone and small amounts of isopropanol. At the same time the amine is quantitatively oxidized to the corresponding nitroxide I (Fig. 7, reaction (17)) ... 

Escambia (1) A process for oxidizing isobutene to a-hydroxy-isobutyric acid (HIBA), for use as an intermediate in the manufacture of methacrylates. The oxidant was dinitrogen tetroxide, N204. Operated by the Escambia Chemical Corporation, FL, in 1965 before its destruction by an explosion in 1967. It has not been used again. 

Ruthenium(in) catalyses the oxidative decarboxylation of n-butyric acid and isobutyric acid by ceric sulfate in aqueous acid. A mechanism for the Ru(III)-catalysed oxidation of o-hydroxybenzoic acid by an acidic solution of bromamine-B (PhS02-NNaBr, BAB) has been proposed based on a kinetic smdy. An ionic mechanism is suggested for the ruthenium(III) analogue of the Udenfriend-type system Ru(III)-EDTA-ascorbate-02, for the selective oxygen-atom transfer to saturated and unsaturated hydrocarbons. The kinetics of the oxidation of p-XC6H4CHPhOH(X =... 

The catalytic properties Co-POM/Si02 were assessed in oxidation of IBA to isobutyric acid [96] and a-pinene to verbenol/verbenone [97] with molecular oxygen as well as in a-pinene/lBA co-oxidation to produce the corresponding epoxide and carboxylic acid [97]. In turn, the catalytic performance of Ti-POM/Si02 was examined in a-pinene oxidation to... 

Hydroxy-2-mcthylpropanoic acid, E, can be obtained enantiomerically pure from isobutyric acid by a microbiological oxidation. The aldehyde F is available from a natural product, pulegone, also in enantiomerically pure form. 

ISOBUTYRIC ACID (Table IV) Deuterium oxide Methylene iodide Water... 

Bulk type 11 Oxidation of H2, oxidative dehydrogenation of cyclohexene, isobutyric acid. 

This reaction is another possible route for the production of methacrylic acid, since isobutyric acid can be obtained by an oxo process from propene and CO. Heteropoly compounds and iron phosphates are so far the most efficient catalysts for the reaction. The favorable role of the presence of an a-methyl group is remarkable for oxidative dehydrogenation, as the heteropoly compounds are not good catalysts for the dehydrogenation of propionic acid (338, 339). 

In the dehydrogenation of isobutyric acid, the by-products in addition to CO and C02 are propylene and acetone. Two reaction mechanisms were proposed (340, 341) and the latter is shown in Scheme 9 (340). The formation of methacrylic acid and acetone involves a common intermediate The El elimination of a proton from I yields the methacrylic acid while a nucleophilic SN1 attack of oxide ion produces C02 and acetone (344). On the other hand. 

The selective oxidation of aromatic portions of molecules was demonstrated using model compounds such as toluene, ethylbenzene, n-propylbenzene and iso-propylbenzene (28.) The major oxidation products from these compounds were acetic, propionic, butyric and isobutyric acids respectively. In each case the carboxylic acid group marks the position that the aromatic unit used to occupy. 

For acid catalysis, the rates of bulk-type reactions show close correlations with the bulk acidity, while the catalytic activities for surface-type reactions are related to the surface acidity which is sensitive to the surface composition and often change randomly. Similarly, in the case of oxidation catalysis, good correlations exist between the oxidizing ability of catalyst and the catalytic activity for oxidation in both bulk-type and surface-type reactions. Acid and redox bifunctionality is another characteristic of HPAs. For example, the acidity and oxidizing ability work cooperatively for the oxidation of mcthacrolcin, whereas they function competitively for the oxidative dehydrogenation of isobutyric acid [5]. Interestingly, the former is of surface type and the latter of bulk type. 

Attempts have been made to relate spectroscopic quantities and catalytic behavior. Kim et al. (2007) correlated the performance of heteropoly acid catalysts in isobutyric acid oxidative dehydrogenation (ODH) to the position of the absorption edge after treatment at 603 K. 

Herzog et al. (1994) Ag Oy, heteropoly molybdates Phase transformations, nature of active phase + + + Partial oxidation of isobutyric acid... 

---