Two-phase medium

Equation (22) was obtained, essentially, with examination of the energy balance equation with respect to flows of gas-containing polymer melts. The key moment of this analysis is, in our view, comprehension of the fact that the energy of gas dissolved in the polymer is transformed into the energy of movement of the two-phase medium. 

The diazo transfer reaction between p-toluenesulfonyl azide and active methylene compounds is a useful synthetic method for the preparation of a-diazo carbonyl compounds. However, the reaction of di-tert-butyl malonate and p-toluenesulfonyl azide to form di-tert-butyl diazomalonate proceeded to the extent of only 47% after 4 weeks with the usual procedure." The present procedure, which utilizes a two-phase medium and methyltri-n-octylammonium chloride (Aliquat 336) as phase-transfer catalyst, effects this same diazo transfer in 2 hours and has the additional advantage of avoiding the use of anhydrous solvents. This procedure has been employed for the preparation of diazoacetoacetates, diazoacetates, and diazomalonates (Table I). Ethyl and ten-butyl acetoacetate are converted to the corresponding a-diazoacetoacetates with saturated sodium carbonate as the aqueous phase. When aqueous sodium hydroxide is used with the acetoace-tates, the initially formed a-diazoacetoacetates undergo deacylation to the diazoacetates. Methyl esters are not suitable substrates, since they are too easily saponified under these conditions. 

Rikvold and Stell [319,320,365] have developed an expression for the partition coefficient in a random two-phase medium made up of spherical particles. They found the partition coefficient to be essentially an exponential function of the solute radius, which is in qualitative agreement with the Ogston theory. 

FIG. 2 Localization of the biocatalyst with different phase distributions of substrate and product in two-phase medium. S substrate P product B biocatalyst. 

FIG. 5 Rate of hydroperoxide production in (a, ) lipoxygenation in pure aqueous medium, (b, ) lipoxygenation in biphasic system, (c, x) two-enzyme (lipase-lipoxygenase) system in two-phase medium, determined experimentally, and (d, ) modeled kinetic of the two enzyme system. (From Ref 63.)... 

When the initial LA concentration is large, the quantity of substrate transferred to the aqueous phase allows the lipoxygenation to progress. This reaction consumes LA and produces HP, which favor the transfer of residual substrate between the two phases. Then catalysis and transfer have a reciprocal influence on each other. We demonstrated that the use of a non-allosteric enzyme in a compartmentalized medium permits the simulation of a co-operativity phenomenon. The optimal reaction rate in the two-phase system is reached for a high initial LA concentration 14 mM. Inhibition by substrate excess is observed in two-phase medium. 

Most research has been performed in a two-phase medium with no flow conditions very little has been done in two-phase-flow systems. Although the flow condition may bring in new variables, such as slip ratio, it is reasonable to assume that the basic phenomena observed in the nonflow condition also occur in the flow condition. 

Heat transfer between gas and particle phases tend to be efficient due to the large volumetric concentration of interface surface. Hence this topic is rarely of significant concern and will not be dealt with in this chapter. Most of the chapter concerns heat transfer between the two-phase medium and submerged surfaces. This is the most pertinent engineering problem since heat addition or extraction from the fluidized or conveyed mixture is commonly achieved by use of heat exchangers integral to the vessel wall or submerged in the particle/gas medium. 

A short review of light scattering from biphasic systems will be helpful We shall consider the scattering to arise from a two-phase medium with average polarizability a and local inhomogeneities n(r) a(r)-a ... 

In this respect the dense nonporous ion-exchange material of a membrane may be viewed as a one-phase medium. In contrast to this a porous bulk ion-exchanger (e.g., an ion-exchange bed or a single microporous ion-exchange bead) is a two-phase medium with the possibility for each ion to be in either one of the two phases—in the ion-exchange matrix proper or in the aqueous pore. 

In this case a platinum anode wich is not sensitive to organic contamination can be used giving a current yield for Cr(VI) of 94%. Electrolyses can be performed in a two-phase medium making an in-cell process possible This method has been applied to the synthesis of benzaldehyde from benzylic alcohol giving 100% current yields at 10 % conversion while the current yield drops to 60 % at high conversions. 

The reaction takes place in a two-phase medium. Secondary alcohols form ketones (90%), primary alcohols and aldehydes are oxidized to carboxylic acids (60-77%), 1,2-diols are cleaved to carboxylic acids (75%), 1,4- and 1,5-diols are transformed to lactones and keto acids (75 %). 

Fig. 8. Dependence of effective thermal conductivity of a two-phase medium A-B (randomly positioned overlapping spheres of phase B in continuous phase A) on the ratio of component conductivities (from Kohout et al., 2004).

An alternative procedure is available for the preparation of iodocarbonates which utilizes homoallylic carbamates as the starting material. For example, (/f )-( )-5-(aminocarbonyloxy)-l-benzyloxy-2,8-nonadiene [12, R1 = ( )-CH2OBn R2 = (CH2)2CH = CH2 R3 = H]9 with two equivalents of iodine in a two-phase medium consisting of diethyl ether and sodium hydrogen carbonate solution at 20 CC affords the corresponding cyclic iodocarbonate 13, a precursor of 1,3,5-triols1 °, in 76% yield and 93 7 (cis1,traits ) selectivity. 

As an oxometal component, osmium tetroxide is the most reliable reagent on the laboratory scale to produce c/s-diols. Ruthenium tetroxide in the presence of NaI04 effects oxidative cleavage of olefins [4], but has been successfully employed for so-called lightning dihydroxylation reactions using a two-phase medium [6]. 

In a two-phase medium, diethyl 1-oxopropylphosphonate is oxidized with H2O2 to give diethyl... 

A point to note is that for optimnm yields, radical snbstitntions are often not taken to Ml conversion (of starting heterocycle), but as product and starting material are often easily separated this is usually not a problem. Ways of avoiding disubstitution include control of pH (when the product is less basic than the starting material) or the use of a two-phase medium to allow removal of a more lipophilic product from the aqueous acidic reaction phase. 

More practically significant, are the many examples of nucleophilic addition to salts in which an N-substituent conjugates with the nitrogen, and thus stabilizes the product - Reissert compounds were the first examples. These are produced by cyanide addition to an iV -acyl-quinolinium or -isoquinolinium salt in the classical process the acylating agent is benzoyl chloride. Reissert compounds are traditionally prepared using a dichloromethane-water two-phase medium improvements include utilising phase-transfer... 

Bedeaux, D., Kapral, R. The effective reaction rate and diffusion coefficients for a two-phase medium,/. Cbem. Pbys., 79, 1783-1788 (1983). 

The site-selectivity of oxidations by mCPBA is demonstrated in the conversion of (4 R = Me or Ph) into the corresponding ene epoxide (5). The product is sensitive to acid, so that the conversion is accomplished in a basic two-phase medium. Normal epoxidation of (6) with mCPBA leads to (7), The stereochemistries for such reactions are shown in the predominant formation of the 3-epoxide (8) (81%) from the parent alkene, with 12% of the a-product. Similar epoxidation of the cannabinol (9) leads to a less stereo-specific isomer distribution of 27.3% and 18.2%. Remarkable stereoselectivity has been shown in the epoxidation of the 14,15-unsaturated oestratrienes (10). Whereas oxidation of 17j3-esters and 17/3-ethers gave 14a,15a-epoxides (< 59%), the 17j3-urethane derivatives displayed a s /w-directive effect to yield 14/3,15j3-epoxides (< 87%). 

In order to understand the iron sulfide-inhibitor interaction,it will be necessary to review briefly the corrosion mechanism of iron in the presence of hydrogen sulfide in a two-phase medium. 

F. Cheng, L. Guifeng, F. Jianxin, and Z. Jingwu, Characterisation of carbox-ymethyl cellulose synthesized in two phase medium C th -C2H5OH. I. Distribution of substituent groups in the anhydroglucose unit, J. Appl. Polym. Sci., 61 (1996) 1831-1838. 

Differential equations (3.33) and (3.34) are easily solved for stationary regime of axial symmetric non-swirling turbulent flow of incompressible Newton two-phase medium without consideration of inter-phase heat- and mass-transfer. That is why the force of inter-phase interaction... 

A synthesis of p,p-carotene (3) provides an interesting combination of sulphone and Wittig chemistry (Scheme 19). Condensation of the C2o-sulphonaldehydes 70-72 with the retinylphosphonium salt 73 is carried out in a two-phase medium (dichloromethane/aqueous KOH) p,P"Carotene (3) is obtained from the Wittig condensation products 74-76 by elimination [87]. 

In 1951, Jarrouse found that the reaction of aqueous-soluble sodium cyanide (NaCN) and organic-soluble 1-chlorooctane (I-C8H17CI) is dramatically enhanced by adding a small amount of quaternary ammonium salt (R4N X , or Q X", Q R4N ). The reaction is almost complete and a 95% conversion is obtained within two hours when a catalytic amount of tetra-n-butylammonium chloride ((C4H9)4N C1 , or Q CL, Q (C4H9)4N ") is added. The mechanism of the reaction of sodium cyanide and 1-chlorooctane in organic solvent/water two-phase medium is expressed as... 

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