Acetone as co-solvent

An enantioselective nitrilase from Pseudomonas putida isolated from soil cultured with 2 mM phenylacetonitrile was purified and characterized. This enzyme is comprised of 9-10 identical subunits each of 43 kDa. It exhibits a pH optimum at 7.0 and a temperature optimum at 40 °C (Ty2 = 160 min) and requires a reducing environment for activity. This nitrilase was shown to have an unusually high tolerance for acetone as co-solvent, with >50% activity retained in the presence of 30% acetone. The kinetic profile of this nitrilase reveals KM= 13.4mM, cat/ M = 0-9s 1mM 1 for mandelonitrile, ZfM = 3.6mM, kclJKM 5.2 s him-1 for phenylacetonitrile, and KM = 5.3 mM, kC lt/KM = 2.5 s 1 him 1 for indole 3-acetonitrile. Preliminary analysis of this enzyme with 5 mM mandelonitrile revealed formation of (/t)-mandelic acid with 99.9% ee [59]. 

C4C1im][PF6] 0s04 NMO Enantioselective dihydroxylation of olefins with H20 and acetone as co-solvents products extracted with tert-butyl methyl ether. Use of a charged chiral PHAL-ligand. [66]... 

QC mltPFs] K2[0s02(0H)4] NMO Enantioselective dihydroxylation of trans-stilbene with H20 and acetone as co-solvents and (DQ)2PHAL or (DFIQ)2PFIAL as ligand products extracted with diethyl ether. [68]... 

In order to improve the solubility of KMn04 in alkylamines, especially secondary ones, polar solvents were used. For instance, treatment of 3-nitropyridine with diethylamine and KMn04 in DMSO gave 6-diethylamino derivative in 60% yield, while without DMSO the reaction did not occur at aU (Scheme 11) [59]. As isolation of the target product in the presence of DMSO is rather complicated, alkylamination of l,2,4-triazine-4-oxides with dialkylamines (such as MeaNH, EtaNH, pyrrolidine, piperidine, and morpholine) and KMn04 can be carried out in acetone, as co-solvent [60]. 

So far, the most common experimental conditions used for the oxidation of alcohols with chromic acid are the so-called Jones oxidation first described in 1946, in which acetone is used as co-solvent. In fact, the use of chromic acid in the oxidation of alcohols has a long tradition in organic synthesis. As soon as in the 19th century, Beckmann described335 an oxidation of alcohol with aqueous chromic acid, in which no mixing of phases was... 

QCjimJtPFe] CjimlfSbFs] 0s04 NMO Enantioselective dihydroxylation of aryl olefins with acetone-H20 as co-solvent 2.5-5 equivalents of chiral ligand added products extracted with Et20 catalyst reused four times, marked decrease in activity after the third run. [67]... 

This effect was confirmed by calculation of the loading of the free phenol molecule and the complex phenol-sulfolane (expressed as the number of loaded molecules in a crystal elementary unit of TS-1), using the software Sorption (Cerius 2), which turned out to be 13.6 and 0.8, respectively. Alternatively, the protective effect exerted by sulfolane can be evaluated by measuring the reaction rate, expressed as the turnover frequency (TOF moles of reacted substrate/moles of Ti per hour) for the oxidation of benzene and phenol, carried out separately in acetone and sulfolane as co-solvents. In the case of acetone, the phenol oxidation (TOF = 190) was ten times faster than that measured for benzene (TOF = 19) conversely, operating in sulfolane the rate measured for phenol (TOF = 51) was only 1.6 time higher than that measured for benzene (TOF = 31), according to the higher value of the observed selectivity. 

The use of supercritical CO2 to extract AR from cereal material was only recently presented (49). Pure supercritical CO2 was not able to extract AR even at pressures as high as 35 MPa and SS C. This result was attributed to the amphiphilic character of the AR and the non polar character of the supercritical CO2. With the addition of 10% of ethanol or methanol, it was possible to obtain extracts even at near the critical pressure (8 MPa). The optimal pressure was determined to be 3SMPa at S5°C when ethanol or methanol acted as co-solvent. The co-solvent was added as 10%wAv of the CO2. The CO2 flow was kept constant at Sg/min during the experiments. A comparison of the supercritical CO2 extraction with die addition of ethanol and classical extraction methods was made. For the classical method, pure acetone extraction at O.IMPa and 20°C was used. Between 15 and 30 MPa at 55°C, 8 to 80%w/w higher yields of AR crude extracts for the extraction with supercritical CO2 with co-solvents were obtained than for pure acetone extraction (refer to figure 2). However, the HPLC analysis of the extracts showed similar composition (49). 

Other studies seem to indicate, however, that care must be exercised when such ternary systems include small, polar solutes. Low molecular weight, polar solvents, in particular alcohols, are used extensively as co-solvents in natural products and other extractions employing SCCO2 [18]. The polar solvent acts as a modifier of gas-phase polarity and enhances the solubility of polar species that would otherwise exhibit limited solubility in CO2. The effect of solvents such as ethanol and acetone was investigated [13,19] by measuring the solubility of [BMIM][PF6] in CO2 in the presence of these solvents (Figure 5). 

Polar, aprotic solvents such as acetone, DMF, DMSO, and HMPA are often used alone or as co-solvents for Sf 2 reactions. 

In this study, the nanofibers of copolymer P(VDF-TrFE) with different VDF contents were prepared by electrospinning. Based on previous work, acetone and DM F were chosen as co-solvent to prepare the solution, and the concentration was 12wt%. All the nanofibers were produced under the high voltage of 12 kV and appropriate solution feeding rate of 1.6 mb h. ... 

Hydrogen peroxide was used to oxidize sulphoxides to sulphones at an early stage in the development of organosulphur chemistry28 and has remained the reagent of choice for everyday laboratory oxidations of this type. Typically, an excess of 30% hydrogen peroxide in water is employed at room temperature, often with a co-solvent such as an alcohol or acetone. 

To suppress the noncatalyzed reaction (which decreases the enantioselec-tivity) between acetone cyanohydrin and the substrate, ethyl acetate is required as a co-solvent, and a low reaction temperature is also essential. Han et al.22 found that in organic solution with a trace amount of water the above reaction proceeds with the same high enantioselectivity as in the presence of an aqueous buffer. The reaction can be carried out at a wide range of temperatures from 0° to 30° C. To avoid using highly toxic potassium or sodium cyanide, acetone cyanohydrin is used as a cyano donor. 

Solvent effects for a series of thienopyridine derivatives, 49, have been studied. In organic solvent/water mixtures, the values, ranging from 8.75 to 10.44, are found to be dependent on both the amount and the type of organic solvent (dimethylformamide (DMF), methanol, ethanol, and acetone) used in the mixture, with pA(a values increasing as the organic co-solvent concentration increases <2003CED1495>. 

Although the procedure for the O-methylation of the carbinol from acetylene and acetone (exp. 2.4) gives a fair yield, it is less suitable for the O-methyladon of alcohols that are not available in large amounts. In such cases there is need for a very clean high-yield method. The procedure for the O-methylation of ethynylcyclohexanol meets this condition. Ethynylcyclohexanol can be O-lithiated quantitatively by BuLi in a mixture of THF and hexane. Since O-alkylations of lithium alkoxides in solvents of moderate polarity proceed very sluggishly (even in the case of methyl iodide), a sufficient amount of the polar DMSO has to be added as a co-solvent. The methyladon with methyl iodide can then be accomplished under relatively mild conditions and there is no indication for decomposition of the lithium carbinolate into LiCsCH and cyclohexanone. 

The compound [PPN][Mn2(/i-PPh2)(CO)8] is an orange, air-stable solid. It is soluble in tetrahydrofuran, acetone, and chlorinated solvents, moderately soluble in alcohols and toluene and insoluble in water and hydrocarbon solvents. Solutions of [PPN][Mn2(ju-PPh2)(CO)8] are surprisingly stable as compared to most other transition metal carbonyl anions, decomposing only slowly (days) on exposure to air and/or moisture. The carbonyl IR spectrum of the anion in dichloromethane shows absorptions at 2037 (m), 1947 (s), 1941 (vs), 1914(w), 1888(m), and 1872(m).3... 

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