Hexane solubility parameter

The Effect of Catalyst Concentration The first parameter that was studied was the effect of the catalyst concentration. Samples impregnated with 1, 5, 10 and 15% tin as stannous chloride and a sample with no catalyst were hydrogenated at 450°C to investigate the effect that increasing catalyst concentration has on the composition of the oil (hexane soluble portion) formed. 

With traditional solvents, the solvent power of a fluid phase is often related to its polarity. Compressed C02 has a fairly low dielectric constant under all conditions (e = 1.2-1.6), but this measure has increasingly been shown to be insufficiently accurate to define solvent effects in many cases [13], Based on this value however, there is a widespread (yet incorrect ) belief that scC02 behaves just like hexane . The Hildebrand solubility parameter (5) of C02 has been determined as a function of pressure, as demonstrated in Figure 8.3. It has been found that the solvent properties of a supercritical fluid depend most importantly on its bulk density, which depends in turn on the pressure and temperature. In general higher density of the SCF corresponds to stronger solvation power, whereas lower density results in a weaker solvent. 

FIGURE 3 2 Solvent extraction efficiencies (EF) as functions of dielectric constants (D), solubility parameters (6), and polarity parameters (P and E -). Solvents studied silicon tetrachloride, carbon disulfide, n pentane. Freon 113, cyclopentane, n-hexane, carbon tetradiloride, diethylether, cyclohexane, isooctane, benzene (reference, EF 100), toluene, trichloroethylene, diethylamine, chloroform, triethylamine, methylene, chloride, tetra-hydrofuran, l,4 dioxane, pyridine, 2 propanol, acetone, ethanol, methanol, dimethyl sulfoxide, and water. Reprinted with permission from Grosjean. ... 

This scale ranges from 7.3 for n-hexane to 23.4 for water. Compounds with higher solubility parameters are generally more polar or hydrophilic than those with lower solubility parameters. The solubility parameter of Hildebrand and Scott (36, 37) has been subdivided into... 

The E s of the nonpolar solvents, CF3CI and C2H4, become equal to tnat of n-hexane at a pressure in the range of 1-2 kilobar. Notice that the Hildebrand solubility parameters of these three solvents are roughly equivalent at this condition of constant E. The same result is also observed for the polarizabilities/ volume of these solvents. Again, the molar densities of these supercritical fluids are considerably higher than that of n-hexane at this equivalence point in solvent strength, since the polarizabilities/molecule are lower. 

It is possible to determine C quantitatively using Hildebrand s theory of microsolutes. An example of the accuracy that can be achieved is provided by the calculation of the solubilities of a series of p-aminobenzoate esters in hexane (17,18). Michaels, et al. (19) used this approach to estimate the solubility of steroids in various polymers. The solubilities of seven steroids in six polymers were calculated from the steroid melting points, heats of fusion, and solubility parameters. Equation 8 was derived, where Jjj is the maximum steady state flux, h is the membrane thickness, x is the product of V, the molar volume of the liquid drug, and the square of the difference in the solubility parameters of the drug and polymer, p is the steroid density, T is melting point (°K), T is the temperature of the environment, R is the gas constant, and AH and ASf are the enthalpy and entropy of fusion, respectively. 

This polarity index measures the intermolecular attraction between a solute and a solvent, whereas the Hildebrand solubility parameter is defined for pure solvent. For example, ether is not very polar and has a Hildebrand value of 7.4—about the same as hexane, which has a value of 7.3. However, ether can accept protons in the form of hydrogen bonds to its nonbonding electron pairs, and consequently its polarity index is 2.8 compared to 0.1 for hexane. 

Benzene is termed a good solvent for polystyrene since Its solubility parameter (6=9.2H) Is within a previously established range of 1.8 for polystyrene (6=9.2H). When hexane (6=7.3H) was used at the same concentration, very little polymerization retardation was observed. The intrinsic viscosity and GPC elution times of the polymer resulting from the hexane modified emulsion Indicated it was substantially lower in molecular weight than the control. 

As shown In Figure 4, the rate of polymerization of styrene was retarded by good nonvlscous solvents such as benzene, cyclohexane, and octane whose solubility parameters (6) were within 1.5H of that of polystyrene at styrene to additive ratios of 3 to 1. The absolute rates were slightly Increased In poorer nonvlscous solvents such as heptane and hexane and were fastest In viscous nonsolvents such as dllsoctyl phthalate and Nujol. Rate studies Indicated a Rp dependency on [E] substantially greater than unity for the styrene emulsion systems modified with viscous poor solvents. 

Octanol is a hydrogen-bonding solvent, and thus it shows certain specificity in its ability to dissolve some components. For example, K, for phenol in hexane is only 0.11 while in octanol it is equal to 29.5. There were several attempts to rationalize solvent effects using solubility parameters [15], dielectric constant [16], and others, but none appear to be consistent. n-Octanol gives the most consistent results with other physicochemical properties and drug absorption in gastrointestinal tract. 

The solubility-parameter approach provides a useful framework for the choice of the mode of liquid chromatography that is best suited for a given analyte. However, solubility parameters of solutes are often unavailable and the solubility of an analyte in water, methanol and hexane provides a more pragmatic basis for the choice of chromatographic system. Figure 3.4 shows that low molecular weight analytes (RMM < 1000) may be divided into those that are water soluble and... 

As the data in Table 4.3 show, the solubility parameter reflects how a chemist might rank these solvents in terms of polarity, e.g. water as the most polar (highest 5) and hexane as the least polar (lowest 8) but also one of the difficulties with this measurement of polarity is highlighted. The solubility parameter suggests that tetrahydrofuran (THE) and carbon tetrachloride are very similar even though carbon tetrachloride is immiscible with water whilst THE is miscible with water in all proportions. A similar comparison may be made between chloroform (8 = 19.1, water-immiscible) and acetone (8 = 20.2, water-miscible). 

The static mode uses both organic solvents such as toluene [27], methanol [28] or acetone [29] and solvent mixtures (usually in a 1 1 ratio) including dichloromethane-acetone [20,28], acetone-hexane [30,31], heptane-acetone [31], acetone-isohexane [32] or methanol-water [33], The use of mixed solvents as extractants provides improved extraction in terms of expeditiousness and recovery [20,28,30-35] as a result of the solubility parameter for a binary mixture being roughly proportional volumewise to the parameters of its components [36], Thus, in the extraction of Irganox 1010 from polypropylene, the addition of 20% of cyclohexane to 2-propanol doubles the extraction... 

They were the calculation of the Hildebrand solubility parameter as a function of density using tabulated thermodynamic data for carbon dioxide and Raman spectroscopy of test solutes dissolved in supercritical carbon dioxide compared to liquid solvents to evaluate solvent-solute interactions. The results of these recent approaches indicated that while the maximum solvent power of carbon dioxide is similar to that of hexane, probably somewhat higher, there is some solvent-solute interaction not found with hexane as the solvent. The limiting solvent power of carbon dioxide is resolved by choosing the alternative of a supercritical fluid mixture as the mobile phase. The component added to the supercritical fluid to increase its solvent power and/or to alter the chromatograph column is referred to as the "modifier."... 

As already mentioned, in evaluating the dispersive component of the solubility parameter in the literature, reference is usually made to the homomorph concept. The homomorph is typically the hydrocarbon with the structure closest to the studied substance. The homomorph of n-pentanol, for example, is n-hexane and of isopropanol is isobutane. The homomorph concept may be used with the present approach as well. Equation 2.36 indicates how to use it The homomorph and the studied substance should be brought at the same reduced density — a type of corresponding states. Table 2.5 also includes the calculated homomorph component, 8, of the solubility parameter. 

Denote the solubility parameter components of MEK, n-hexane and polystyrene using superscripts i, j and k, respectively. 

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