Atmosphere Over Reaction

The dehydrogenation of 2-butanol is conducted in a multitube vapor-phase reactor over a zinc oxide (20—23), copper (24—27), or brass (28) catalyst, at temperatures of 250—400°C, and pressures slightly above atmospheric. The reaction is endothermic and heat is suppHed from a heat-transfer fluid on the shell side of the reactor. A typical process flow sheet is shown in Figure 1 (29). Catalyst life is three to five years operating in three to six month cycles between oxidative reactivations (30). Catalyst life is impaired by exposure to water, butene oligomers, and di-j -butyl ether (27). 

Euleria.n Models. Of the Eulerian models, the box model is the easiest to conceptualize. The atmosphere over the modeling region is envisioned as a well-mixed box, and the evolution of pollutants in the box is calculated following conservation-of-mass principles including emissions, deposition, chemical reactions, and atmospheric mixing. 

Like vinyl acetate from ethylene, allyl acetate is produced by the vapor-phase oxyacylation of propylene. The catalyzed reaction occurs at approximately 180°C and 4 atmospheres over a Pd/KOAc catalyst ... 

The reaction conditions are approximately 200°C and 30 atmospheres over a cobalt-based catalyst. 

The first step is the liquid phase addition of acetic acid to butadiene. The acetoxylation reaction occurs at approximately 80°C and 27 atmospheres over a Pd-Te catalyst system. The reaction favors the 1,4-addition product (l,4-diacetoxy-2-butene). Hydrogenation of diacetoxybutene at 80°C and 60 atmospheres over a Ni/Zn catalyst yields 1,4-diacetoxybu-tane. The latter compound is hydrolyzed to 1,4-butanediol and acetic acid ... 

The hydrogenation reaction occurs at approximately 270°C and slightly above atmospheric over a Cu/Silica catalyst. About a 95% yield is obtained. 

Dissolve 20pmol of PE (15 mg) in 2 ml of argon-purged, anhydrous methanol containing 20 pmol of triethylamine (2 mg). Maintain the solution over an argon or nitrogen atmosphere. The reaction also may be done in dry chloroform. Note Methanol or chloroform and TEA should be handled in a fume hood. 

To a solution of thioglycoside (1.0 equiv), 1-benzenesulfinyl piperidine (1.0 equiv), TTBP (2.0 equiv), and freshly activated 3 A powdered molecular sieves in dichloromethane (25.0 ml mmol-1) was added trifluoromethanesulfonic anhydride (1.1 equiv) at —60 °C under an argon atmosphere. The reaction mixture was stirred for 5 min, after that a solution of the glycosyl acceptor (1.5 equiv) in dichloromethane (4.0 ml mmol-1) was added. The reaction mixture was stirred at — 60 °C for 2 min, after that it was slowly warmed to room temperature and quenched by the addition of saturated aqueous NaHC03. The organic layer was washed with brine, dried (MgS04), filtered and the filtrate was concentrated to dryness. Purification of the crude product by column chromatography over silica gel afforded the product. 

The thioglycoside donor is dissolved in CH2C12 ( 0.1 M) and cooled to — 78 °C under an inert atmosphere. wCPBA (70wt%, 1.2 equiv) is then added portionwise with minimal exposure to the atmosphere. The reaction mixture is warmed to room temperature over lh, at which time TLC shows the dissappearance of starting material and the formation of more polar compounds. The sulfoxides are purified by column chromatography over silica. 

Direct ( hydrogenative ) Cj cyclization of alkanes to give saturated C5 cyclic products. This is a typical metal-catalyzed reaction occurring in a hydrogen-rich atmosphere over a narrow group of metals (25). 

Despite the fact that reaction (1) is often cited, erroneously, as responsible for the NO to N02 conversion in the atmosphere, elementary reaction kinetics can be used to demonstrate that this cannot be the case. Even in a highly polluted atmosphere, the conversion of NO to N02 occurs over a period of several hours. Reaction (1) is kinetically second order in NO in both the gas and liquid phases (e.g., DeMore et al., 1997 Lewis and Deen, 1994). Following the conventions discussed in Chapter 5.A.1, the rate law for reaction (1) can be written as follows ... 

A mixture of 1 (100 mg, 0.2 mmol) and ammonium trifluoromethanesulfonate (377 mg, 2.2 mmol) in THE (10 mL) was reacted with NaBH(OEh)3 (2 equiv) at room temperature under an argon atmosphere. The reaction was monitored by TLC analysis. After the reaction was complete, the solvent was removed by a rotary evaporator, the mixture extracted with ethyl acetate, dried over anhydrous Na2S04, and concentrated. 

Methane is removed continually from the atmosphere by reaction with OH radicals (Section 8.3). In contrast, chlorofluorocarbons and related volatile compounds are inert under the conditions of the lower atmosphere (troposphere), so atmospheric concentrations of these refrigerants and solvents will tend to increase as long as releases continue. The chief concern over chlorofluorocarbons is that they are a major factor in destruction of the stratospheric ozone layer (Section 8.3). They have been banned under the Montreal Protocol of 1988, but it is important that whatever substitutes (inevitably greenhouse active) are introduced to replace them degrade relatively quickly in the troposphere to minimize any contribution they may be capable of making to greenhouse warming. 

A solution of 4,4,17a-trimethyl-androsta-2,5-dien-17p-ol-3-one in benzene was added to sodium methoxide (from sodium and of absolute methanol, concentrating the solution and drying the residue for 1 h at 150°-160°C and 15 mm). Ethyl formate was then added with stirring in a nitrogen atmosphere. The reaction mixture was stirred for 4 h at room temperature, allowed to stand for about 15 h, stirred for 2 h and then poured into water. The reaction mixture was extracted with benzene, the aqueous layer warmed until clear, filtered and cooled below room temperature. Concentrated hydrochloric acid and ice were added to the filtrate until the mixture was acid to Congo red, and the product was extracted with chloroform. The chloroform extracts were washed with water, dried over anhydrous sodium sulfate, filtered and concentrated vacuum, whereupon there separated 2-hydroxymethylene-4,4,17a-trimethyl-androsta-2,5-dien-17p-ol-3-one. 

NCS)2] (51), and TBA[Ir(ppy)2(NCO)2] (52). These complexes were conveniently synthesized under inert atmosphere by reaction between the dichloro-bridged Ir dimer [Ir(ppy)2(Cl)]2 in dichloromethane solvent with an excess of a pseudohalogen ligand such as tetrabutylammonium cyanide, tetrabutyl-ammonium thiocyanate, or tetrabutylammonium isocyanate, respectively, with over 70% yields [77]. 

Trichlorosilane (77 pL, 0.77 mmol) was added dropwise to a stirred solution of the imine (100 mg, 0.51 mmol) and catalyst (13.5 mg, 0.051 mmol) in anhydrous toluene (2 mL) at 0 °C, and the mixture was stirred at r.t. overnight under an argon atmosphere. The reaction was quenched with a saturated solution of NaHCC>3 (10 mL) and the product was extracted with ethyl acetate (3 x 30 mL). The extract was washed with brine, dried over anhydrous MgSC>4, and the solvent was evaporated. Purification using column chromatography on silica gel with a petroleum ether-ethyl acetate mixture (24 1) afforded the (S)-(+)-amine (81 mg, 81%, 92% ee) as an oil [a]D + 16.8 (c 0.5, MeOH). 

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