Mixed isobutyl

Liquid-liquid extractions using ammonium pyrrolidine dithiocarbamate (APDC) as a metal chelating agent are commonly encountered in the analysis of metal ions in aqueous samples. The sample and APDC are mixed together, and the resulting metal-ligand complexes are extracted into methyl isobutyl ketone before analysis. 

The principal commercial source of 1-butanol is -butyraldehyde [123-72-8] obtained from the Oxo reaction of propylene. A mixture of n- and isobutyraldehyde [78-84-2] is obtained in this process this mixture is either separated initially and the individual aldehyde isomers hydrogenated, or the mixture of isomeric aldehydes is hydrogenated direcdy and the n- and isobutyl alcohol product mix separated by distillation. Typically, the hydrogenation is carried out in the vapor phase over a heterogeneous catalyst. For example, passing a mixture of n- and isobutyraldehyde with 60 40 H2 N2 over a CuO—ZnO—NiO catalyst at 25—196°C and 0.7 MPa proceeds in 99.95% efficiency to the corresponding alcohols at 98.6% conversion (7,8) (see Butyraldehydes Oxo process). 

For the estimation of vanillin, T. von Fallenburg proposes to make use of the colour produced by treating a dilute aqueous solution with isobutyl alcohol and concentrated sulphuric acid. Five c.c. of the solution are mixed with 5 c.c. of a 1 per cent isobutyl alcohol solution in 95 per cent, alcohol, and 25 c.c. concentrated sulphuric acid, the colour produced being compared after forty-five minutes with that given by known amounts of vanillin. 

M Preparation of isopropyiidene peniciiiamine hydrochioride To the filtrate obtained In step (b) is added at 20°C to 25°C a total of 85 g of hydrogen sulfide. The precipitated HgS is filtered off and the filtrate is concentrated under reduced pressure to a volume of 200 to 500 ml. Following e polish filtration, the product-rich concentrate is mixed with 1.5 liters of isobutyl acetate. The mixture is refluxed at about 40 C under reduced pressure in equipment fitted with a water separation device. When no further water separates, the batch is cooled to 30t and filtered. The reactor is washed with 1 liter of acetone, which Is used also to wash the cake. The cake is further washed with 200 ml of acetone. The acetone washes are added to the isobutyl acetate filtrate and the mixture is refluxed for 20 to 30 minutes. After a holding period of one hour at 5°C, the crystals of isopropyiidene penicillamine hydrochloride are filtered and washed with 200 m of acetone. On drying for twelve hours at 25°C this product, containing 1 mol of water, weighs about 178 g (73%). 

To set the stage for the crucial aza-Robinson annulation, a reaction in which the nucleophilic character of the newly introduced thiolactam function is expected to play an important role, it is necessary to manipulate the methyl propionate side chain in 19. To this end, alkaline hydrolysis of the methyl ester in 19, followed by treatment of the resulting carboxylic acid with isobutyl chlorofor-mate, provides a mixed anhydride. The latter substance is a reactive acylating agent that combines smoothly with diazomethane to give diazo ketone 12 (77 % overall yield from 19). 

Like the carbodiimide method, the mixed anhydride method results in an amide complex (Table 5, Figure 17). The acid-containing hapten is dissolved in a dry, inert, dipolar, aprotic solvent such as p-dioxane, and isobutyl chloroformate is added with an amine catalyst. The activated mixed anhydride is chemically stable and can be isolated and characterized. The aqueous protein solution is added to the activated acid and the pH is maintained at around 8.5. A low temperature (around 10 °C) is necessary during the reaction to minimize side reactions. 

The complexes [(n-C4H9)4N]2[MS4C4(CN)4], where M = Co, Ni, Cu, and Rh are isomorphous, and mixed single crystals can be grown very easily using the acetone-isobutyl alcohol solvent pair and only slight modifications of the recrystallization procedure. 

The mash from the Streptomyces aureofaciens fermentation broth is acidified and filtered. The filtrate is adjusted to the desired pH, usually 7-8.5, and various flocculating or chelating agents may be added (e.g., vinyl acetate-maleic anhydride copolymer, sodium EDTA, ammonium oxalate, Arquad). The precipitate is (1) stirred with filter aid, filtered, stirred with HC1, refiltered, mixed with 2-ethoxyethanol, filtered, washed, and the filtrates are combined, acidified with HC1, NaCl is added, and the crystals are collected, washed with 2-ethoxyethanol, water, and ethanol, and dried (67), or (2) extracted into methyl isobutyl ketone, the extracts are combined, filtered, and acidified with HC1, and the crystals are collected and washed with water, 2-ethoxyethanol, and isopropanol, and vacuum-dried. If the crystals are greenish, they are treated with sodium hydrosulfite at pH 1.8, filtered, washed, and dried as in (1) above (68). 

Mixed anhydrides. Ethyl chloroformate and isobutyl chloroformate are the reagents most often used. 

Enamel Preparation. Soluble oligoester diols (Ib-ld, 2a-2g, and 3a-3g), HMMM, methyl isobutyl ketone (MIBK) and -toluenesulfonic acid ( -TSA) were thoroughly mixed in a 70/30/30/0.3 wt. ratio. The solution was cast on panels and baked at 150" for 30 min. Less soluble LC diols le-lg were melted, dispersed in MIBK, mixed with HMMM and -TSA in the above proportions and immediately cast as films. Oligoester diol la was too insoluble for enamel formation. 

The Z-protected derivative, again prepared by standard methods using benzyl chloroformate,t208 may serve in the case of racemic pipecolic acid for resolution into the pure enantiomers by fractional crystallization with L-tyrosine hydrazide/208 Acylation with N-protected pipecolic acid or of pipecolyl peptides is performed by standard procedures via the active ester methods, e.g. A-hydroxysuccinimide ester/121 by the mixed anhydride method, e.g. with isobutyl chloro-formate 95-114 or pivalic acid chloride/121 as well as by DCC/HOBt/118 In the synthesis on solid support, longer coupling times are required when compared to N-protected proline.1[235 ... 

Some of the versions of the mixed anhydride technique discussed may involve components other than a-hydroxy acids. Therefore, the resultant products cannot be considered as main-chain modified peptidomimetics. However, on many grounds these methods are of general importance in depsipeptide synthesis. For example the classical peptide reagent isobutyl chloroformate appears to be suitable for ester bond formation through the corresponding mixed anhydride with Boc- or Z-protected amino acids and the Thr (3-hydroxy group in the synthesis of a number of natural peptide lactones.145 7 ... 

The complex tra//.s-[AuMe2-t-Bu(PPh3)], prepared by addition of methyl iodide to the mixed dialkylaurate(I), was found (230) to convert spontaneously to the corresponding isobutyl complex in solution. First-order kinetic behavior was observed, and the rate was diminished by the addition of free triphenylphosphine, and so a dissociative mechanism was proposed (Scheme 8). The isopropyl analog did not react similarly at room temperature, and heating caused reductive elimination. 

Procedure Approx 60 mg of the mixt is dissolved in 40 ml of a methyl isobutyl ketone-isopropanol mixt (4 1) and titrated with sodium methoxide added from a microburet. After each ad dition of the titrant, the soln is thoroughly mixed by a magnetic stirrer for 1 min and the potentials recorded after allowing the soln to settle for another min. The titration is cote ducted in an atm of nitrogen. An av erage recovery of 99 75% with a standard deviation. of 0.38 is to to be expected. See also Analytical Procedures under HMX in this Volume... 

Protected amino acids or peptides are activated at the carboxy group by the mixed anhydride method using isobutyl chloroformate and NMM and reacted with ethereal diazomethane to form the corresponding peptidyl diazomethyl ketone (Scheme 1). The diazomethane solution is prepared from TV-methyl-A -nitroso-d-toluenesulfonamide (Diazald, Aldrich) or l-methyl-3-nitro-l-nitrosoguanidine (MNNG, Aldrich) according to the supplier s instruction (Aldrich information bulletin No. Al-180). No racemization occurs when diazomethyl ketones are prepared by this method. 

They are colourless or yellowish-brown liquids and sometimes have unpleasant, irritating odours. The specific gravity is about 0-83 at 150 C. and the boiling point ranges from 800 to 160° C., the maximum distillation products being obtained at about 130°. The principal components are higher alcohols of the fatty series, mostly amyl, isobutyl and propyl alcohols. These oils do not mix with water. 

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