Organic phase control

It is assumed that the organic reaction rate in the organic phase is much higher than the substitution reaction rate in the organic phase. Controlling the reaction could eliminate the effect of the organic reaction. 

Extraction of Pd + with [QP] [Cl] and [QP] [Bis] is very fast and the equilibrium is achieved after 5 minutes (Fig. 4) contrary to the case when dialkyl sulphides are used in conventional PGMs extraction. The increase in HCl concentration affects Pd + extraction, which decreases from more than 90 to near 50% for 0.1 and 3 M HCl, respectively (Fig. 5). Moreover, spontaneous transfer of Pd2+ to the organic phase, controlled by diffusion, is observed that suggests great mobility of the interface system. 

The distribution of highly extractable solutes such as and Pu between the aqueous and organic phases is strongly dependent upon the nitrate anion concentration in the aqueous phase. This salting effect permits extraction or reextraction (stripping) of the solute by controlling the nitric acid concentration in the aqueous phase. The distribution coefficient, D, of the solute is expressed as... 

The porosity of polymer beads is controlled by the ratio of diluents (poro-gen) to monomers in the organic phase. The increase in the ratio of diluents to monomer in the monomer mixture increases the porosity of polymer beads. The pore size can be manipulated by adjusting the ratio of nonsolvating and solvating diluents in the monomer mixture. The increase in the ratio of nonsolvating diluent (precipitant) in the monomer mixture increases the pore sizes and vice versa. 

From these general characteristics a number of criteria for sulfonation configurations can be derived. The combination of an instantaneous reaction, with considerable exothermic heat effect and a factor 50-100 increase in viscosity in the organic phase, makes it clear that proper temperature control in the organic phase is the main problem in practice. 

Aqueous-organic two-phase reaction has been widely performed [18]. One of the purposes of using two-phase reaction system is to control the substrate concentration in aqueous phase where the biocatalysts exist. Hydrophobic substrate and products dissolve easily in the organic phase, so that the concentration in the aqueous phase decreases. The merits of controlling and decreasing the substrate concentration in the aqueous phase are as follows ... 

Because a chemical step is imposed on top of the physical distribution process of partition, there is a great potential for selectivity, as noted by Schill et al, (49>50), Such factors as pH, type and composition of the organic phase, and ionic strength of the aqueous phase can be used to control relative retention. The concentration and type of counterion mainly control the absolute retention. 

P 9] DL-l-Phenylethylamine and 4-amino-l-benzylpiperidine were dissolved in 0.1 M NaOH aqueous solution [23]. 3-Nitrobenzoyl chloride and 3,5-dinitrobenzoyl chloride were used as ethyl acetate solutions. The concentration of all reactants was set to 0.01 M. Syringe pumps served for liquid feed. The flow rate was 50 plmin and room-temperature processing was applied. No further temperature control was exerted as the reaction is only mildly exothermic. After having passed the micro reactor, the phases were settled in test-tubes and the organic phase was withdrawn for analysis. 

A more detailed study of this system using benzene and toluene has been reported by Soede et al. (1993) from The Netherlands. They have shown that the role of ZnS04 is to make the Ru hydrophlilic so that the catalyst particles are surrounded by a stagnant water layer. This aids in the rapid removal of the cyclohexene from the catalyst surface to the organic phase. The reaction is operated in mass transfer controlled conditions. 

A second liquid phase may be deliberately employed in an emulsified form to gain advantages similar to those cited earlier for organic processes. Such two-phase systems, and even two-phase enzymatic reactions, allow both the electrochemistry and organic chemistry to take place in their optimum medium. Further, the aqueous phase allows acidity to be controlled in the organic medium and the organic phase allows the desired intermediate product to be extracted to improve yields. 

The CLM method is a new technique, developed by Nagatani and Watarai [61]. This method produces a stable, ultrathin two-phase liquid membrane by the centrifugal force due to the rotation of a cylindrical cell, using the arrangement shown in Fig. 11. The inner diameter and inner height of the cylindrical cell were 19 and 29 mm, respectively. The rotation speed was controlled in the range 6000-7500 rpm. The summation of the absorption spectra of both interfacial and bulk organic phase species was measured in the direction perpendicular to the rotation axis with a diode array spectrophotometer. 

The shape of steady-state voltammograms depends strongly on the geometry of the microhole [13,14], Wilke and Zerihun presented a model to describe diffusion-controlled IT through a microhole [15], In that model, a cylindrical microhole is assumed to be filled with the organic phase, so that a planar liquid-liquid interface is located at the aqueous phase side of the membrane. Assuming that the diffusion is linear inside the cylindrical pore and spherical outside [Fig. 2(a)], the expression for the steady-state IT voltammo-gram is... 

The facilitated transfers of Na+ and K+ into the NB phase were observed by the current-scan polarography at an electrolyte-dropping electrode [12]. In the case of ion transfers into the DCE phase, cyclic voltammetry was measured at an aqueous gel electrode [9]. Both measurements were carried out under two distinctive experimental conditions. One is a N15C5 diffusion-control system where the concentration of N15C5 in the organic phase is much smaller than that of a metal ion in the aqueous phase. The other is a metal ion diffusion-control system where, conversely, the concentration of metal ion is much smaller than that of N15C5. Typical polarograms measured in the both experimental systems are shown in Fig. 2. 

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