Aqueous tert-butanol

The TS-1 catalyst exhibits some quite remarkable activities and selec-tivities, e.g. ethylene is epoxidized with 30% H2O2 in aqueous tert-butanol at ambient temperature, affording ethylene oxide in 96% selectivity at 97% H202 conversion. 

Using potassium osmate (0.5-2 mol%) in the presence of an organic base, e.g. quinuclidine, in aqueous tert-butanol at pH 10.4, a variety of olefins was converted to the corresponding vie-diols in high yield. Apparently reoxidation of os-mium(VI) to osmium(VIII) with dioxygen is possible under alkaline conditions. When chiral bases were used asymmetric dihydroxylation was observed (see Section 4.7) albeit with moderate enantioselectivities. 

The presence of water in the reaction medium is required for the hydrolysis of the intermediate osmate esters. Although aqueous tert-butanol is the solvent system of choice, MTBE has been used in a large-scale application [2[. 

The alkylation of the sulfide 96, the formation of the ylid 99, and the reaction with the aldehyde are all carried out in one operation. The sulfide is a good nucleophile for alkyl halides and forms the sulfonium salt 98. This gives the ylid 99 with NaOH as a convenient base in aqueous tert-butanol. The ylid selectively attacks the aldehyde to give the betaine 100 that closes to the epoxide and releases the sulfide 96 for the next round. 

The reaction is usually run in aqueous acetone in either one- or two-phase systems, but substrate solubility may require the use of other solvents. Aqueous tert-butanol, tetrahydrofuran, and mixtures of these solvents have also been used successfully. 

Asymmetric dihydroxylation of the side-chain of Z-1-(4-meth-oxyphenyl)-1-(tert-butyldimethylsiloxy)-1-propene to give (R)-l-hydroxyethyl 4-methoxyphenyl ketone in 94% yield (99% e.e.) was effected by addition of the alkene to a stirred mixture of osmium tetroxide, potassium ferricyanide, potassium carbonate, a 9-0-(9 -phenanthryl)ether(PHN) of dihydroquinidine and 1 mole of methanesulphonamide in aqueous tert-butanol (1 1), with reaction during 16 hours at ambient temperature. Then treatment with sodium sulphite prior to work-up to gave the product (ref. 130). Other best ligands were the 9-0-(4 -methyl-2 -quinolyl) ethers (MEQ) of dihydroquinine. 

Subsequently, stoichiometric asymmetric aminohydroxylation was reported. Recently, it was found by Sharpless that through the combination of chloramine-T/Os04 catalyst with phthalazine ligands used in the asymmetric dihydroxylation reaction, catalytic asymmetric aminohydroxylation of olefins was realized in aqueous acetonitrile or tert-butanol (Scheme 3.3). The use of aqueous tert-butanol is advantageous when the reaction product is not soluble. In this case, essentially pure products can be isolated by a simple filtration and the toluenesulfonamide byproduct remains in the mother liquor. A variety of olefins can be aminohydroxylated in this way (Table 3.1). The reaction is not only performed in aqueous medium but it is also not sensitive to oxygen. Electron-deficient olefins such as fumarate reacted similarly with high ee values. 

Similar cyclizations of N-protected amino acids are mediated under surprisingly mild conditions by CuBr (10 mol%) in aqueous tert-butanol (1 1) at ambient... 

Unusual 2-amino-IP 155 derivative was claimed to be formed in poor yield when 2-(3,5-dichloropyridyl-2-amino)pyrimidine 154 was subjeeted to UV radiation (Hg lamp, 400 W) in aqueous tert-butanol (93ZOR2035). 

The second major discovery regarding the use of MTO as an epoxidation catalyst came in 1996, when Sharpless and coworkers reported on the use of substoichio-metric amounts of pyridine as a co-catalyst in the system [103]. A change of solvent from tert-butanol to dichloromethane and the introduction of 12 mol% of pyridine even allowed the synthesis of very sensitive epoxides with aqueous hydrogen peroxide as the terminal oxidant. A significant rate acceleration was also observed for the epoxidation reaction performed in the presence of pyridine. This discovery was the first example of an efficient MTO-based system for epoxidation under neutral to basic conditions. Under these conditions the detrimental acid-induced decomposition of the epoxide is effectively avoided. With this novel system, a variety of... 

Tauber et al. [23] following the same method as Hart et al. but using tert-butanol as the methyl radical source, obtained a temperature of 3,600 K in 10 3 M /(77-butanol and reported, similar to Hart et al. that this temperature decreased with increasing /( / /-butanol concentration. More recently, this method was adopted by Rae et al. [24] and Ciawi et al. [25, 26] in aqueous solutions. Rae et al. examined the effect of concentration of a series of aliphatic alcohols, extrapolating a maximum temperature of about 4,600 K at zero alcohol concentration [24]. They also observed a decrease in temperature with increasing alcohol concentration, which correlated well with the alcohol surface-excess and SL measurements obtained in the same system. Ciawi et al. investigated the effects of ultrasound frequency, solution temperature and dissolved gas on bubble temperature [26],... 

The nickel oxide electrode is generally useful for the oxidation of alkanols in a basic electrolyte (Tables 8.3 and 8.4). Reactions are generally carrried out in an undivided cell at constant current and with a stainless steel cathode. Water-soluble primary alcohols give the carboxylic acid in good yields. Water insoluble alcohols are oxidised to the carboxylic acid as an emulsion. Short chain primary alcohols are effectively oxidised at room temperature whereas around 70 is required for the oxidation of long chain or branched chain primary alcohols. The oxidation of secondary alcohols to ketones is carried out in 50 % tert-butanol as solvent [59], y-Lactones, such as 10, can be oxidised to the ketoacid in aqueous sodium hydroxide [59]. 

The enzyme may be dissolved in a mixed aqueous-ionic liquid medium, which may be mono- or biphasic or it could be suspended or dissolved in an ionic liquid, with little or no water present. Alternatively, whole cells could be suspended in an ionic liquid, in the presence or absence of a water phase. Mixed aqueous-organic media are often used in biotransformations to increase the solubility of hydrophobic reactants and products. Similarly, mixed aqueous-ionic liquid media have been used for a variety of biotransformations, but in most cases there is no clear advantage over water-miscible organic solvents such as tert-butanol. 

Styrene is difficult to purify and keep pure. Usually contains added inhibitors (such as a trace of hydroquinone). Washed with aqueous NaOH to remove inhibitors (e.g. tert-butanol), then with water, dried for several hours with MgSO4 and distd at 25° under reduced pressure in the presence of an inhibitor (such as 0.005% p-rert-butylcatechol). It can be stored at -78°. It can also be stored and kept anhydrous with Linde type 5A molecular sieves, CaH2, CaSO4, BaO or sodium, being fractionally distd, and distd in a vacuum line just before use. Alternatively styrene (and its deuterated derivative) were passed through a neutral alumina column before use [Woon et al. JACS 108 7990 1986 Collman JACS 108 2588 7986]. 

The densities and volumetric specific heats of some alkali halides and tetraalkylammonium bromides were undertaken in mixed aqueous solutions at 25°C using a flow digital densimeter and a flow microcalorimeter. The organic cosolvents used were urea, p-dioxane, piperadine, morpholine, acetone, dime thy Isulf oxide, tert-butanol, and to a lesser extent acetamide, tetrahydropyran, and piperazine. The electrolyte concentration was kept at 0.1 m in all cases, while the cosolvent concentration was varied when possible up to 40 wt %. From the corresponding data in pure water, the volumes and heat capacities of transfer of the electrolytes from water to the mixed solvents were determined. The converse transfer functions of the nonelectrolyte (cosolvent) at 0.4m from water to the aqueous NaCl solutions were also determined. These transfer functions can be interpreted in terms of pair and higher order interactions between the electrolytes and the cosolvent. 

Mark G, Schuchmann MN, Schuchmann H-P, von Sonntag C (1990) The photolysis of potassium peroxodisulphate in aqueous solution in the presence of tert-butanol a simple actinometer for 254 nm radiation. J Photochem Photobiol A Chem 55 157-168 Mark G, Korth H-G, Schuchmann H-P, von Sonntag C (1996) The photochemistry of aqueous nitrate revisited. J Photochem Photobiol A Chem 101 89-103 Mark G, Tauber A, Laupert R, Schuchmann H-P, Schulz D, Mues A, von Sonntag C (1998) OH-radical formation by ultrasound in aqueous solution, part II. Terephthalate and Fricke dosimetry and the influence of various conditions on the sonolytic yield. Ultrason Sonochem 5 41-52 MarkG, Schuchmann H-P, von Sonntag C (2000) Formation of peroxynitrite by sonication of aerated water. J Am Chem Soc 122 3781-3782... 

A DS of up to 1.0 is obtained in one step by applying optimised reaction conditions 3.8 M aqueous NaOH, reaction temperature of 60 °C for 90 min in tert-butanol/water or isopropanol/water 85 15 (v/v) mixtures (Table 12) [219]. The DS of CMD can be increased by repeated carboxymethy-lations. CMD with DS 1.5 was realised by two-step carboxymethylation. Under optimal conditions, the applied NaOH solution was 3.8 M. The DS value is decreased with lower NaOH concentrations because of incomplete activation of the hydroxyl groups, and also with higher NaOH concentrations due to increasing side reactions of MCA with NaOH forming glycolic acid [280]. 

To a mixture of 50 g 2-[4-[(4-chlorophenyl)phenylmethyl]-l-piperazinyl]-ethanol and 225 ml of tert-butanol at 45°C under a nitrogen was added 21 g tert-BuOK. The temperature was raised to 75-80°C and the mixture was kept at this temperature. After 45 min was added 11 g sodium chloracetate after 1.5 hour was added 5.2 g tert-BuOK after 2 hours was added 5.64 g sodium chloracetate after 2.5 hours was added 1.9 g tert-BuOK after 3 hours was added 1.9 g sodium chloracetate after 3.5 hours was added 0.8 g tert-BuOK and after 4 hours was added 1.13 g sodium chloracetate. Then about 150 ml tert-butanol was distilled of, 190 ml of water was added and the distillation of tert-butanol was continued until the temperature of the vapour reaches 100°C. To the reaction mixture was added 60 ml of water and 8 ml concentrated hydrochloric acid to pH 8. Unreacted 2-[4-[(4-chlorophenyl) phenylmethyl]-l-piperazinyl]-ethanol was extracted with diethyl ether. The aqueous phase was acidified to pH 5 by addition of hydrochloric acid and extracted with dichloromethane (200 ml x 3). The extract was dried over MgS04, filtered and concentrated in a rotary evaporator. An obtained oil was allowed to crystallize by addition of 150 ml of 2-butanone, yields of 2-[4-[(4-chlorophenyl)phenylmethyl]-l-piperazinyl]-ethoxy]acetic acid 55.5%, M.P. 146-148°C. 

Purified by paper chromatography using tert-butanol-water, cutting out the main spot and eluting with water. Also purified by adsorption onto an apo-flavodoxin column, followed by elution and freeze drying Crystd from acidic aqueous soln. [Mayhew and Strating Eur J Biochem 59 539 1976.]... 

The alcohols used were 1-propanol and tert-butanol (with and without deuteration of the hydroxyl group) from Aldrich . The preparation of WZ (W content 6 wt%) is described elsewhere [2]. In brief, the catalyst is obtained by aqueous incipient wetness impregnation of hydrous zirconia with a solution containing the appropriate amount of ammonium metatungstate. The sample is subsequently calcined at 1096 K for one hour under flowing air. EXAFS measurements carried out at the National Synchrotron Light Source [7] showed that the WZ sample has an average W-O coordination number and distance of 4.7 and 1.69 A respectively. The surface area of the calcined material is 36 m /g. XRD reveals that a small amount of monoclinic zirconia was formed upon calcination. The Y-zeolite catalyst was... 

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