Methanol dielectric constants, dipole moments

We have no measurements of micellar size, since the translation of micelle size into the number of monomers in the micelle is not a simple task and requires assumptions not easily experimentally tested. We are hopeful of extending experimentation in this direction in future research. Table II lists dielectric constants, dipole moments and effective polarities for methanol, 1- and 2-octanol, and water at 25°C. 

Table II. Dielectric Constants, Dipole Moments and Effective Polarities for Methanol, Octanols and Water at 25°C...

Figure 8.5 Prediction of the water and methanol dielectric constant as a function of dipole moment fi (lD 3.33564-10 C-m) from the SAFT-VR-I-DE equation of state at room temperature and pressure. and , the theoretical predictions - -----------, the experimental value of the dielectric con-...

The results of the measurements made have proved the suppositions formulated on the ground of Kamiehski s studies. Generally they can be formulated thus the dielectric constant of the liquid should not much exceed the dielectric constant of the solid phase the electrical momentum of the solvent s particles should not be too great. In relation to metal powders water is a good solvent of electrol5de. For other powders we have achieved the best results by applying methanol and ethanol (adding 0.5 g of KCl to a litre of pure methanol or to a litre of rectified alcohol in case of ethanol). Water, ethanol, and methanol have stable dipole moments of their molecules rather near and less than 2. 

Many of the properties oj -hydroxypyridines are typical of phenols. It was long assumed that they existed exclusively in the hydroxy form, and early physical measurements seemed to confirm this. For example, the ultraviolet spectrum of a methanolic solution of 3-hydroxypyridine is very similar to that of the 3-methoxy analog, and the value of the dipole moment of 3-hydroxypyridine obtained in dioxane indicates little, if any, zwitterion formation. However, it has now become clear that the hydroxy form is greatly predominant only in solvents of low dielectric constant. Comparison of the pK values of 3-hydroxypyridine with those of the alternative methylated forms indicated that the two tautomeric forms are of comparable stability in aqueous solution (Table II), and this was confirmed using ultraviolet spectroscopy. The ratios calculated from the ultraviolet spectral data are in good agreement with those de-... 

Comparison of dipole moments shows only small differences in polarity. From these data, it can be reasoned that micellization in methanol is feasible. Dielectric constants and effective polarities (dipole moment/molar volume) support this premise with more divergent values. It is noted that bis(2-ethyIhexyI) sodium sulfosuccinate forms micelles readily in water and 2-octanol which have the highest and lowest dielectric constants, respectively, but micelles are formed only at low concentrations in methanol whose dielectric constant is intermediate in value. 

Solute/Cosolvent/Solvent Systems. Solubilities of solids may be modified by adding a small concentration of a nonpolar hydrocarbon (e.g. propane, octane) or a polar molecule (e.g. acetone, methanol). CO2 has a small polarizability and no dipole moment, so additives increase the polarizability of the solvent (i.e. the refractive index of Equation 7) and the dielectric constant (Equation 3). Polar cosolvent molecules also interact with functional groups on the solutes. Cosolvents may increase solubilities up to an order of magnitude although the enhancement is dependent on cosolvent concentration. Unfortunately, relatively few fundamental cosolvent studies are published at this time. 

From the chemical viewpoint, methanol is a simple small molecule completely miscible with water. It has a hi dipole moment and hi dielectric constant and is associated in its liquid state. It is therefore a good solvent for ionizable substances, such as acids and salts, as well as for certain plastics. Gasoline, on... 

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