A-hydroxyisobutyrate

Fig. 3. The elution of tnpositive actinide and lanthanide ions. Dowex-50 ion-exchange resin was used with ammonium a-hydroxyisobutyrate as the eluant.

Actinide ions of the 111, IV, and VI oxidation states can be adsorbed by cation-exchange resins and, in general, can be desorbed by elution with chloride, nitrate, citrate, lactate, a-hydroxyisobutyrate, ethylenediaminetetraacetate, and other anions (11,12). 

Selected physical properties of various methacrylate esters, amides, and derivatives are given in Tables 1—4. Tables 3 and 4 describe more commercially available methacrylic acid derivatives. A2eotrope data for MMA are shown in Table 5 (8). The solubiUty of MMA in water at 25°C is 1.5%. Water solubiUty of longer alkyl methacrylates ranges from slight to insoluble. Some functionalized esters such as 2-dimethylaniinoethyl methacrylate are miscible and/or hydrolyze. The solubiUty of 2-hydroxypropyl methacrylate in water at 25°C is 13%. Vapor—Hquid equiUbrium (VLE) data have been pubHshed on methanol, methyl methacrylate, and methacrylic acid pairs (9), as have solubiUty data for this ternary system (10). VLE data are also available for methyl methacrylate, methacrylic acid, methyl a-hydroxyisobutyrate, methanol, and water, which are the critical components obtained in the commercially important acetone cyanohydrin route to methyl methacrylate (11). 

Arguably the key step in the MGC process is the conversion of a-hydroxyisobutyramide to methyl a-hydroxyisobutyrate using methyl formate as the methylating agent. Methyl formate is made commercially by MGC via vapor-phase dehydrogenation of methanol (72). 

The reaction is mn for several hours at temperatures typically below 100°C under a pressure of carbon monoxide to minimise formamide decomposition (73). Conversions of a-hydroxyisobutyramide are near 65% with selectivities to methyl a-hydroxyisobutyrate and formamide in excess of 99%. It is this step that is responsible for the elimination of the acid sludge stream characteristic of the conventional H2SO4—ACH processes. Because methyl formate, and not methanol, is used as the methylating agent, formamide is the co-product instead of ammonium sulfate. Formamide can be dehydrated to recover HCN for recycle to ACH generation. 

The methyl a-hydroxyisobutyrate produced is dehydrated to MMA and water in two stages. First, the methyl a-hydroxyisobutyrate is vaporized and passed over a modified zeoHte catalyst at ca 240°C. A second reactor containing phosphoric acid is operated at ca 150°C to promote esterification of any methacrylic acid (MAA) formed in the first reactor (74,75). Methanol is co-fed to improve selectivity in each stage. Conversions of methyl a-hydroxyisobutyrate are greater than 99%, with selectivities to MMA near 96%. The reactor effluent is extracted with water to remove methanol and yield cmde MMA. This process has not yet been used on a commercial scale. 

Hydroxy-2-methylpropionic acid (a-hydroxyisobutyric acid, 2-methyllactic acid)) [594-6I-6J M 104.1, m 79 , b 114 /12mm, 212 /760mm, pK 3.78. Distd in steam, crystd from diethyl ether or benzene, sublimed at 50° and dried under vacuum. 

N-Ethy I-N-2-hydroxy ethylamine Hydroxychloroquine sulfate Ethyl a-hydroxyisobutyrate Trimethadione Ethyl iodide... 

C4H9NO2 13027-88-8) see Dimethadione D(-)-3-bydroxyisobutyric acid (C4HSO3 1910-47-0) see Captopril a-hydroxyisobutyric acid (C4H,03 594-61-6) see Dimethadione... 

Kemp and Waters also found the oxidations of cyclohexanone and of mandelic, malonic and a-hydroxyisobutyric acids by Cr(VI) to be Mn(II)-catalysed. In these cases, as with oxalic acid, the [Cr(VI)] versus time plots are almost linear and the reaction becomes first order in substrate (or involves Michaelis-Menten kinetics), and, except at lowest catalyst concentrations, approximately first order in [Mn(II)]. Detailed examination of the initial rate of oxidation of a-hydroxyrobutyric acid as a function of oxidant concentration revealed, however, that the dependence is... 

C-C fission to give IV for both V(V) and Mn(III). Kemp and Waters have established two main features of these oxidations, namely, (i) for the oxidations of QH5CD(0H)C02H and the light compound are V(V), 2.0 Mn(III) sulphate, 1.2 Ce(lV) sulphate, 1.1 and (i7), that the trend of rates of oxidation of mandelic, a-hydroxyisobutyric, lactic and glycollic acids is as expected for Ce(IV) and Mn(III) if stabilisation of the radical RCHOH is important, but is altered for V(V) (Fig. 4). It appears from the latter observations that the presence of a-hydrogen atoms causes a drop in rate by a factor of almost 10 per a-hydrogen... 

Methyl alcohol. See Methanol Methyl a-cyclogeranate, 24 569 Methyl a-hydroxyisobutyrate, 16 247 Methyl allyl carbonate, molecular formula, 6 305t... 

The enthalpies and entropies of formation of mono-mandelato-complexes have been determined and, in comparison with other hydroxycarboxylic acid complexes, the enthalpy order of stabilization is lactate > a-hydroxyiso-butyrate mandelate > glycolate, whereas the entropy order of stabilization is glycolate > a-hydroxyisobutyrate > mandelate > lactate. The stability constants and enthalpy of formation of mono- and di-malonate complexes have also been measured.The mono-1,1-cyclopentanedicarboxylato-complexes are less stable than the corresponding malonate species. 

Japanese group has prepared [2- C]5,5-dimethyl-2,4-oxazohdinedione 230, the penultimate precursor to [2- C]trimethadione via condensation of [ C]urea with ethyl a-hydroxyisobutyrate. 

Problem 16.1 Give a derived and lUPAC name for the following carboxylic acids. Note the common names, (a) CH,(CH,) COOH (caproic acid) (b) (CH,),CCOOH (pivalic acid) (c) (CH,)X HCH,CH,COOH ( y-methylvaleric acid) (d) C H,CH,CH,COOH (/3-phenylpropionic acid) (e) (CH,),C(OH)COOH (a-hydroxyisobutyric acid) (/) H06C(CH,),C00H (succinic acid) (no derived name). ... 

Problem 16.70 Use isopropyl alcohol as the only organic compound to synthesize (a) a-hydroxyisobutyric acid, (h) /3-hydroxy butyric acid. 

The new chemistry is based on a Sr-90/Y-90 separation using a-hydroxyisobutyric acid (a-HIB) and cation exchange chromatography (5). Once the activities are loaded onto the column, the steps to prepare the column for the a-HIB elution remove several of the possibile contaminants including rubidium and cobalt. Finally, the a-HIB elution also removes a wide range of other elements as well, leaving strontium on the ion exchange column (6). 

Hydroxy-5-iodobenzoic acid see 5-iodosaIicylic acid. a-Hydroxyisobutyric acid see 2-hydroxy-2-methylpropionic acid. 

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