Promoters acetone

Although benzenesulphonyl chloride has for simplicity been used in the above discussion, tolucne-/>- sulphonyl chloride, CHaCeH SO Cl, is more frequently used in the laboratory, owing to its much lower cost, the latter being due in turn to the fact that toluene-p-sulphonyl chloride is a by-product in the commercial preparation of saccharin. Toluene-p sulphonyl chloride is a crystalline substance, of m.p. 68° the finely powdered chloride will, however, usually react readily with amines in the Schotten-Baumann reaction it does not react so readily with alcohols, but the reaction may be promoted considerably by first dissolving the chloride in some inert water-soluble solvent such as acetone. 

A Hquid-phase isophorone process is depicted ia Figure 4 (83). A mixture of acetone, water, and potassium hydroxide (0.1%) are fed to a pressure column which operates at head conditions of 205°C and 3.5 MPa (- 500 psi). Acetone condensation reactions occur on the upper trays, high boiling products move down the column, and unreacted acetone is distilled overhead ia a water—acetone a2eotrope which is recycled to the column as reflux. In the lower section of the column, water and alkaH promote hydrolysis of reaction by-products to produce both isophorone and recyclable acetone. Acetone conversion is typically ia the range 6—10% and about 70% yield of isophorone is obtained. Condensation—hydrolysis technology (195—198), and other Hquid-phase production processes have been reported (199—205). 

Solubility and Solvent Resistance. The majority of polycarbonates are prepared in methylene chloride solution. Chloroform, i7j -l,2-dichloroethylene, yy -tetrachloroethane, and methylene chloride are the preferred solvents for polycarbonates. The polymer is soluble in chlorobenzene or o-dichlorobenzene when warm, but crystallization may occur at lower temperatures. Methylene chloride is most commonly used because of the high solubiUty of the polymer (350 g/L at 25°C), and because this solvent has low flammabiUty and toxicity. Nonhalogenated solvents include tetrahydrofuran, dioxane, pyridine, and cresols. Hydrocarbons (qv) and aUphatic alcohols, esters (see Esters, organic), or ketones (qv) do not dissolve polycarbonates. Acetone (qv) promotes rapid crystallization of the normally amorphous polymer, and causes catastrophic failure of stressed polycarbonate parts. 

Since the thermal dehydrocondensation proceeds by a free-radical mechanism (37), various radical-forrning promoters like acetone, ethanol, or methanol have been found useful in improving conversion of ben2ene to condensed polyphenyls. In the commercial dehydrocondensation process, ben2ene and some biphenyl are separated by distillation and recycled back to the dehydrocondensation step. Pure biphenyl is then collected leaving a polyphenyl residue consisting of approximately 4% o-terphenyl, 44% y -terphenyl, 25% -terphenyl, 1.5% triphenylene, and 22—27% higher polyphenyl and tars. Distillation of this residue at reduced pressure affords the mixed terphenyl isomers accompanied by a portion of the quaterphenyls present. 

Pure (9-terphenyl can be obtained by fractional distillation. To obtain high purity m- or -terphenyl, the appropriate distillation fraction has to be further purified by recrysta11i2ing, 2one refining, or other refining techniques. Currently, litde demand exists for pure isomers, and only a mixture is routinely produced. Small amounts of acetone, ethanol, or methanol are used to promote dehydrocondensation, and as a result, minor amounts of methyl- or methylene-substituted polyphenyls accompany the biphenyl and terphenyls produced. For most purposes, the level of such products (<1%) is so small that their presence can be ignored. For appHcations requiring removal of these alkyl-polyphenyl impurities, an efficient process for their oxidative destmction has been described (38). 

Isopropyl Ether. Isopropyl ether is manufactured by the dehydration of isopropyl alcohol with sulfuric acid. It is obtained in large quantities as a by-product in the manufacture of isopropyl alcohol from propylene by the sulfuric acid process, very similar to the production of ethyl ether from ethylene. Isopropyl ether is of moderate importance as an industrial solvent, since its boiling point Hes between that of ethyl ether and acetone. Isopropyl ether very readily forms hazardous peroxides and hydroperoxides, much more so than other ethers. However, this tendency can be controlled with commercial antioxidant additives. Therefore, it is also being promoted as another possible ether to be used in gasoline (33). 

Acetone and ammonia are condensed in the presence of various promoters. A 45 per cent yield of diacetonamine isolated as the hydrogen oxalate is claimed when acetone saturated with ammonia at o" is allowed to stand twenty-four hours with 8.5 per cent of ammonium nitrate. Suzuki and Horie, Bull. Inst. Phys.-Chem. Research (Tokyo) ii, 383 (1932). Abstract 30 (in English) published with Sci. Papers Inst. Phys.-Chem. Research (Tokyo) 18, Nos. 350-4 [C. A. 26, 4302 (1932)]. 

The use of acetone cyanohydrin (in an exchange reaction) instead of alcoholic hydrogen cyanide affords even higher yields of 17-cyanohydrins and the former reagent has the added advantage of reacting quantitatively and essentially selectively with the 17-ketone of androst-4-ene-3,17-dione. Sodium hydroxide promotes the exchange reaction in some cases. 

A simple aliphatic ketone such as acetone, when promoted to its n,n excited state, undergoes a single unimolecular photochemical reaction in high quantum yield namely a-cleavage giving a methyl and acetyl radical which react further in secondary dark processes. In general, competition... 

Fig. 30 Microwave-promoted fluorous synthesis of biaryl-subshtuted proline analogs. Reagents and condihons a EtaN, DMF, MW 150 °C, 15 min, 40-75%, closed vials b R""PhB(OH)2, Pd(dppf)Cl2, K3PO4, toluene Acetone H2O, MW 120 °C, 12 min, sealed vial system, 19-79%. R=Me, Et R = Me, 1 - Pr R" = H, 3-MeO R" =Me, Et R""= 4-MeO, 3-Cl, 4-Ac,3,4-diCl,3,4-methylenedioxy...

Our group has exploited 4-phenylthio-l,3-dioxanes as convenient precursors to 4-lithio-l,3-dioxanes [45,65-69]. 4-Phenylthio-l,3-dioxanes 184 were originally prepared from -silyloxy aldehydes 183 [65] (Eq. 28). Lewis acid-promoted addition of phenylthiotrimethylsilane gave an unstable thioacetal intermediate, which could be converted in situ to the corresponding 1,3-dioxane. Yields for this process are variable, as the product is unstable under the conditions of its formation. The reaction slowly evolves to a mixture of the desired product, the phenylthio acetal of 183, the phenylthio acetal of acetone, and a variety of other unidentified products. 

Experiments were conducted in which purified trichloroethylene (1 mg in acetone) was applied to the shaved backs of female ICR/Ha Swiss mice (Van Duuren et al. 1979). In an initiation-promotion study, a single application of trichloroethylene was followed by repeated application of phorbol myristate acetate (PMA) promoter. In a second study, mice were treated with trichloroethylene three times per week without a promoter. No significant tumor incidences were observed in these studies. Doses used in these studies were well below the maximum tolerated dose, which is often not reached in dermal studies. 

The bis amido complex [Au(bipy)(NHC6H4N02-4)2][Pp6] (43) has been similarly obtained by reaction of 40 with p-nitroaniline in acetone solution (Equation 2.14 in Scheme 2.6) [45b]. Complex 40 promotes the stoichiometric oxidation of various amines different from p-nitroaniline. Azotoluene is the main organic product of the... 

A different type of catalysis is observed using proline as a catalyst.166 Proline promotes addition of acetone to aromatic aldehydes with 65-77% enantioselectivity. It has been suggested that the carboxylic acid functions as an intramolecular proton donor and promotes reaction through an enamine intermediate. 

When the photostabilization of a polymer material is to be obtained through such a surface treatment process, it is all important to make sure that the protective effect will last throughout the service life and therefore to ensure a long-term adhesion of the coating onto the substrate. This can be best achieved by promoting a grafting reaction between the two elements (20). For that purpose, the photoinitiator was partly incorporated in the top layer of the PVC plate by a surface treatment with an acetone solution. Upon UV-irradiation of the resin-coated sample, the following reactions are expected to occur ... 

The radical-promoted reaction between polyethylene and hexafluoro-acetone is shown in Equation 1. It had been demonstrated previously in the case of simple hydrocarbons (8) that the addition of a carbon radical to the carbonyl group of hexafluoroacetone can take place in two modes, to yield the product, of substitution with either a fluoro-... 

Whereas Et3B fails to promote the Ni-catalyzed homoallylation of ketones, Et2Zn successfully promotes the reaction. Some results are illustrated in Scheme 12. Isoprene, for the first time, loses its regioselectivity and reacts with acetone both at Cl and C4 positions to provide a mixture of ho-... 

For certain hindered benzyl esters, tertiary amines are used as promoters. Such hydrogenolyses have been performed over 10% Pd/C in the presence of triethylamine in acetone at room temperature and 30 psi for 18 hours,201 or in t-BuOH at atmospheric pressure for 1.5 hours.202... 

Thus for hydrolysis in 50% aqueous acetone, a mixed second and first order rate equation is observed for phenylchloromethane (benzyl chloride, 10)—moving over almost completely to the SV1 mode in water alone. Diphenylchloromethane (11) is found to follow a first order rate equation, with a very large increase in total rate, while with triphenylchloromethane (trityl chloride, 12) the ionisation is so pronounced that the compound exhibits electrical conductivity when dissolved in liquid S02. The main reason for the greater promotion of ionisation—with consequent earlier changeover to the SW1 pathway in this series—is the considerable stabilisation of the carbocation, by delocalisation of its positive charge, that is now possible ... 

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