Propylene carbonate transfer from water

The following data are for the Gibbs energy of transfer from water to propylene carbonate for 1-1 electrolytes at 25°C [37]. Use these data to estimate the corresponding quantities for the individual ions on the basis of the TATB assumption. 

Fig, 2,12.5. b) Ionic enthalpies of transfer from water to propylene carbonate (after ref. E107). 

Cyclodextrins are often used as inverse phase transfer catalysts [11-14]. They are able to intercalate hydrophobic substances and to transport them into a polar phase like water, where the reaction takes place. To study the influence of cyclodextrins on the isomerizing hydroformylation of frans-4-octene in the biphasic solvent system propylene carbonate/dodecane, the concentration of methylated /3-cyclodextrin was varied from 0.2 up to 2.0 mol.-% relative to the substrate frans-4-octene [24]. The results are given in Table 7. 

Figure 8. Comparison of observed and calculated values for AGt° (molar standard state) for the transfer of salts from water to propylene carbonate. The electrostatic contribution was estimated from Equation 69 with n = 4 (Li+, Na+, K + ), n = 8 (Cl, 04B ), and the following solvated radii in A 3.6 (Li +), 3.9 (Na +), 4.2 (K +), 4.3 (Cl and 6.9 (AB )...

Interface between two liquid solvents — Two liquid solvents can be miscible (e.g., water and ethanol) partially miscible (e.g., water and propylene carbonate), or immiscible (e.g., water and nitrobenzene). Mutual miscibility of the two solvents is connected with the energy of interaction between the solvent molecules, which also determines the width of the phase boundary where the composition varies (Figure) [i]. Molecular dynamic simulation [ii], neutron reflection [iii], vibrational sum frequency spectroscopy [iv], and synchrotron X-ray reflectivity [v] studies have demonstrated that the width of the boundary between two immiscible solvents comprises a contribution from thermally excited capillary waves and intrinsic interfacial structure. Computer calculations and experimental data support the view that the interface between two solvents of very low miscibility is molecularly sharp but with rough protrusions of one solvent into the other (capillary waves), while increasing solvent miscibility leads to the formation of a mixed solvent layer (Figure). In the presence of an electrolyte in both solvent phases, an electrical potential difference can be established at the interface. In the case of two electrolytes with different but constant composition and dissolved in the same solvent, a liquid junction potential is temporarily formed. Equilibrium partition of ions at the - interface between two immiscible electrolyte solutions gives rise to the ion transfer potential, or to the distribution potential, which can be described by the equivalent two-phase Nernst relationship. See also - ion transfer at liquid-liquid interfaces. 

The primary doping process (ion insertion) is the process which occurs in all EPs. It has a major effect on their morphological, mechanical, partitioning and permeation properties. The value of the charge transfer rate also depends strongly on the polymer and on the experimental conditions under which it is formed. Thus, for example, insertion of CIOJ into polypyrrole (PPy) from propylene carbonate is an order of magnitude faster [4] than the insertion of the same anion into polythiophene from water [5]. 

These two effects were clearly seen in a study undertaken by Kara et al. [36]. In their work, PPy doped with bis(trifluoromethanesulfonyl)imide (TFSI) was actuated in various water/propylene carbonate (PC) solutions containing LiTFSI. The optimum performance of 23.6 % maximum strain at a strain rate of 10.8 % s was achieved within an actuation solution that consisted of 60 % water and 40 % PC. Improvements in both the strain rate and the maximum strain were seen with actuation in LiTFSI electrolytes of water/PC blended solvents over actuation in electrolytes of either water or PC alone. The improved actuation was attributed to the fact that a greater swelling occurred from the PC solvent (enabling a faster and easier ion transfer) and an improvement in the ionic conductivity from the water solvent (enabling a better charge transfer). As such, the optimised performance for this system was realised at 40 % PC. 

Figure l.S Transfer enlhalpy for ions of various sizes from water towards propylene carbonate. Reprinted with permission from (19]. Copyright 1969 American Chemical Society... 

These three types of behavior are clearly separated on the transfer enthalpy from water to propylene carbonate for monovalent ions of various sizes [19] (Figure 1.5). The breaking ions, which dcvclo() weaker interactions with water, have the smallest transfer energy. 

Acrolein and condensable by-products, mainly acrylic acid plus some acetic acid and acetaldehyde, are separated from nitrogen and carbon oxides in a water absorber. However in most industrial plants the product is not isolated for sale, but instead the acrolein-rich effluent is transferred to a second-stage reactor for oxidation to acrylic acid. In fact the volume of acrylic acid production ca. 4.2 Mt/a worldwide) is an order of magnitude larger than that of commercial acrolein. The propylene oxidation has supplanted earlier acrylic acid processes based on other feedstocks, such as the Reppe synthesis from acetylene, the ketene process from acetic acid and formaldehyde, or the hydrolysis of acrylonitrile or of ethylene cyanohydrin (from ethylene oxide). In addition to the (preferred) stepwise process, via acrolein (Equation 30), a... 

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