Solvent compositional data

One can interpret the trends in bH and bS in Figures 1-8 in terms of solvation of the reactants or products. Negative values of bH are a possible indication that the products in the reaction are more strongly solvated in solvent S than they are in water. Negative bH values also might indicate that reactants in the reaction are less strongly solvated in solvent S than in water. Conversely, positive values of bH are a possible indication that products are less solvated in solvent S than in water or that reactants are more solvated in solvent S than in water. Another possible factor in the interpretation of bH vs. solvent composition data is the possibility of large contributions of solvent-solvent interactions. 

TABLE II. SOLVENT COMPOSITIONAL DATA (400 °F to 800 °F Boiling Range)... 

In the studies carried out to date, eight fuels have been tested which include six synfuels and two petroleum derived fuels. The synfuels tested included SRC-II middle and heavy distillate fuels, a blend of these fuels, and one SRC fuel blended with the process donor solvent. Composition data for the various fuels are presented in Table I, where it can be seen that the coal derived liquids have a higher C H ratio than either the diesel or residual petroleum oils, indicative of a higher aromatic hydrocarbon content. The shale-derived DFM on the other hand is a highly processed fuel and has a C H ratio similar to the petroleum diesel oil. Complete analyses of all the actual fuels tested were unfortunately not available at the time of writing, and, where necessary, typical analyses have been taken from previous studies. 

Figure 2. Variation of the degree of dissociation of ionic micelles with solvent composition. ( ), Data from emf measurements, (O, O), conductance 4 mobility measurements. D = decyl, DO = dodecyl.

Although it is often possible to predict the effect of the solvent on retention, due to the unique interactive character of both the solvents and the enantiomers, it is virtually impossible to predict the subtle differences that control the separation ratio from present knowledge. Nevertheless, some accurate retention data, taken at different solvent compositions, can allow the retention and separation ratios to be calculated over a wide range of concentrations using the procedure outlined above. From such data the phase system and the column can be optimized to provide the separation in the minimum time, a subject that will be discussed later in the treatment of chromatography theory. 

It is seen that the separation ratio must be greater than about 1.055 for a low efficiency column (2500 theoretical plates) before accurate retention measurements can be made on the composite curve. On the high efficiency columns (10,000 theoretical plates), the separation ratio need only be in excess of about 1.035 before accurate retention measurements can be made on the composite curve. It will be seen later in this chapter that to optimize a column for a difficult separation, accurate retention data must be obtained over a range of temperatures and solvent compositions. It follows that ... 

The effect of changing solvent composition (polarity) on molecular weight dispersity is noteworthy. Mw/Mn is quite low (1.69) in the experiment carried out by the use of 100% CH2C12 and it increases monotonically with increasing n-C6H14 content. It is very difficult to interpret these data at this time. 

Natural ingredients based lipstick formulations have been prepared. The effects of the natural waxes, oils and solvent compositions on the viscosity and melting point of the lipstick have been studied. The result indicates that the viscosity and melting point of the lipstick can be manipulated by changing the composition of natural candelilla wax, camauba wax and beeswax in the formulation. Another important lipstick characteristic, which is hardness, will be studied. Consumer acceptance towards the product will be investigated. Finally, by relating the consumer data and instrumentation analysis, optimisation process will be conducted. 

In all recorded spectra the 3Jee coupling constants between the olefinic protons are on the order of 11-12 Hz, proving the all-E configuration of the investigated carotenoids. Minor differences between the reported chemical shifts and literature data are due to the effect of different solvent compositions. 

Fig. 18 Solubilities at 20°C of the two polymorphs of cimetidine, form A (<9>-) and form B (0), as a function of the mole fraction of 2-propanol in the 2-propanol/water system. Also shown are the solubility ratios (form A/form B) calculated at each solvent composition. (The data are adapted from Ref. 128.)...

FIGURE 14.17 Ultrahigh resolution nano LC-MS separation of base peak chromatogram of 2351 peptides identified in trypsin digest of mouse brain lysate P2 fraction using Micro-Tech XtremeSimple nano-LC and Thermo Electron LTQ. Column 100 cm x 75 fim C18 column, 3 /mi, 8000 psi column head pressure. Solvent composition time 350 min gradient, 5 to 35% B. Solvent A 2% acetonitrile, 0.1% formic acid. Solvent B 95% acetonitrile, 0.1% formic acid. Data analysis Sequest, PeptideProphet, and Protein Prophet. 

Similar results were observed with mixtures of acetone-d6 and methanol-d4, wherein the Rg of the dendrimers is not significantly affected by the fraction of acetone in the solvent. The same result is found over the whole range of temperature studied (i.e. in the range — 10°C data obtained in the solvent compositions, xs = 0.50 show some consistent decrease of Rg, relative to the other solvent compositions. This may indicate the onset of dendrimer shrinkage in the vicinity of the solubility gap, which is around xs 0.52. However, the difference from the a value of Rg for xs = 0.50 < 5% of the mean value of Rg for the other solvent compositions. 

The above points will now be illustrated with respect to the nitro group. The most convenient data for this purpose are for ionization in 50% v/v Et0H-H20124-126. (Data for other solvent compositions are also in the References124,125.) Ap//a values for the effects of in- and p-N02 on the various acids Ph—G—COOH, along with the corresponding Hammett p values (Section n.A), are shown in Table 4. The values of am (calc) and ap (calc) are obtained as cr(calc) = ApK /p. 

When using NMR as a detector for online separations, additional consideration must be given to how the sensitivity is affected by the movement of nuclei past the detector cell. Aside from the physical hardware setup, the chromatographic and spectroscopic parameters also play a role in the quality of the resulting data. Flow rate, solvent composition, and residence and acquisition times can be optimized to provide optimal results. NMR sensitivity and chromatographic resolution tend to have an inverse relationship with respect to online LC-NMR experiments. By slowing the flow rate, more scans can be acquired for a particular analyte in the flow cell, but... 

Figure 6. (a) Optimization of ion conductivity in mixed solvents 1.0 M LiC104 in PC/DME. (b) Dependence of dielectric constant (e) and fluidity (j ) on solvent composition. These plots are reconstructed based on the data reported in refs 187 and 194, respectively. 

Fig. 18 Top CD spectra. Oligomer 15 (solid line) oligomer 15 in the presence of 100 equiv of (-)-a-pinene (dotted line) and 100 equiv of (+)-a-pinene (dashed line) in a mixed solvent of 40% water in acetonitrile (by volume) at 295 K. [15]=4.2 pmol. Bottom Plot of IniCn for 15 against the solvent composition. The solid line is the least-squares linear fit (correlation coefficient=0.9987), and the dotted line is the extrapolation to 100% water. Error bars are from the nonlinear fitting of the data to...

The intrinsic viscosity of PVB is shown as a function of solvent composition for various MIBK/MeOH mixtures in Figure 6. Since [ij] increases with a (see Equation 8), the higher [ly] the better the solvent. Apparently, most mixtures of MIBK and MeOH are better solvents for PVB than either pure solvent. Based on Figure 6, PVB should have a weak selective adsorption of MIBK in a 1 1 solvent mixture and weak adsorption of MeOH in a 3 1 MIBK/MeOH solvent mix. These predictions are in accord with light scattering data discussed previously. The intrinsic viscosity data is also consistent with the second virial coefficient data in Table II in indicating that the 1 1 and 3 1 MIBK/MeOH mixtures are nearly equally good solvents for PVB, the 9 1 mix is a worse solvent, but still better than pure MeOH. 

Experimenters would do well to avoid any unnecessary changes in the ionic composition of reaction samples within a series of experiments. If possible, chose a standard set of reaction conditions, because one cannot readily correct data from one set of experimental conditions in any reliable manner that reveals the reactivity under a different set of conditions. Maintenance of ionic strength and solvent composition is desirable, and correction to constant ionic strength often effectively minimizes or ehminates electrostatic effects. Even so, remember that Debye-Hiickel theory only applies to reasonably dilute electrolyte solutions. Another important fact is that ion effects and solvent effects on the activity coefficients of polar transition states may be more significant than more modest effects on reactants. 

Selectivity for the methylene group has been mostly the focus of interest and was determined by a host of investigators. Data obtained by Karger et al. (148) we shown in Fig. 26. It is seen that the selectivity is a linear ftinction of the solvent composition, when water-methanol mixtures are used as the mobile phase, and decreases with the water content of the eluent. The linearity characteristic of methanol mixtures is absent in the data for water-acetonitrile and water-acetone mixtures but again... 

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