Non-polar substances

CH2CI2. A colourless liquid with a chloroform-like odour b.p. 4I°C. Prepared by heating chloroform with zinc, alcohol and hydrochloric acid manufactured by the direct chlorination of methane. Decomposed by water at 200°C to give methanoic and hydrochloric acids. Largely used as a solvent for polar and non-polar substances, particularly for paint removal (30%), dissolving cellulose acetate and degreasing (10%). It is more stable than carbon tetrachloride or chloroform especially towards moisture or alkali. It is somewhat toxic. U.S. production 1981 280000 tonnes. 

A common approach for personal dosimetry is collection of pollutant on, e.g., silica gel, organic resins or activated charcoal in small tubes worn on the operator s lapel (Table 9.2). Silica gel is useful for polar chemicals charcoal finds wide use for non-polar substances. The pollutant is then solvent-extracted or thermally desorbed for subsequent analysis by, e.g., chromatography. 

Hydrophobic interactions are the single most important stabilizing influence of protein native structure. The hydrophobic effect refers to the tendency of non-polar substances to minimize contact with a polar solvent such as water. Non-polar amino acid residues constitute a significant proportion of the primary sequence of virtually all polypeptides. These polypeptides will fold in such a way as to maximize the number of such non-polar residue side chains buried in the polypeptide s interior, i.e. away from the surrounding aqueous environment. This situation is most energetically favourable. 

COPEs are polar and semicrystalline, which leads to a certain permeability to polar substances such as water and impermeability to non-polar substances such as hydrocarbons. For homologous series, the impermeability increases with hardness. 

Processes of such kinds can be found in the literature. E. Stahl, et al. [1] describe the decontamination of drugs, in particular, the reduction of pesticides from senna leaves by means of supercritical dry carbon dioxide [2]. The patents EP 0382116 A2 [4] and DE 4342874 Al [5] specify processes to remove non-polar substances from ginseng with dense carbon dioxide, in which the ginseng is moisturized prior to extraction, and the second method also uses an entrainer. The European Patent Application EP 0925724 A2 from NATEX [3] explains a process for the removal of plant-protection agents and/or undesired substances from cereals. 

Dipole moments contribute to dielectric constants of liquids or solids. In non-polar substances dielectric constant arises due to molecular polarizability and is generally much smaller than with polar molecules. 

A MicroPak MCH-10 reverse phase column was chosen for separation of the hexane and ether extracts. The monomolecular bonded phase provides efficient separation of both polar and non-polar substances and rapid equilibration to initial activity after gradient elution programs. The reverse phase column provides symmetrical, narrow peaks for the cannabinoic acids, which tend to tail on polar, normal phase columns (e.g. silica). 

More recent staining procedures largely use fluorescent dyes to characterize the physiological and biochemical states of cells. Fluorescein Diacetate (FDA), a non-polar substance which crosses the membrane and is hydrolyzed by intracellular esterases in viable cells to produce fluorescein, exhibits yellow-green fluorescence when excited at 490 nm. Damaged or non-viable cells in general are unable to hydrolyze FDA or to retain fluorescein within the cell [172,173]. In combination with Ethidium Homodimer or Propidium Iodide, a similar esterase substrate, calcein acetoxy methyl ester (CAM) has been found to be reliable for viability assessment of protozoans, but not on Candida yeast, neither on bacteria such as Bacillus cereus and Escherichia coli [174]. 

The consequences of the above results on the partition of aromas and aroma compounds between products and a plastic package can be seen in the values in Table 9-13. It can be seen from the partition coefficients that the values for medium polarity to non-polar substances partitioned between the two wine samples and LDPE are one to two orders of magnitude greater than the partitioning of the same substances between milk and LDPE (limonene, diphenylmethane, diphenyloxide, linalylacetate). The coefficients for the polar substances (cis-3-hexenol, phenyl ethyl alcohol) show comparatively no difference. The K values for non-polar substances partitioned between milk and LDPE are comparable with values obtained for partitioning into 50% ethanol. Despite the relatively low fat content of whole milk (3.5 %), milk behaves quite differently from wine (Kozinowski, 1989). While wine represents a real aqueous solution whose behavior is determined by its water content, milk is not only aqueous but also a fat containing food which, because of its aqueous... 

The second method was developed by Hansen (1967, 1969). Hansen presumed the applicability of Eqs. (7.14) and (7.15) and developed a method for the determination of <5, <5p and c>h for a number of solvents. The value of rid of a given solvent was assumed to be equal to that of a non-polar substance (e.g. hydrocarbon) of about the same chemical structure. This permitted the calculation of Now Hansen deter-... 

You also observed that iodine is soluble in kerosene. Both iodine and kerosene are non-polar substances. The attraction that iodine and kerosene molecules have for each other is greater than the attraction between the iodine molecules in the solid and the attraction between the kerosene molecules in the liquid. 

The Concept Organizer shown on the next page summarizes the behaviour of polar and non-polar substances in solutions. You will learn more about polar and non-polar substances later in this section. 

You have learned that solubility depends on the forces between particles. Thus, polar substances dissolve in polar solvents, and non-polar substances dissolve in non-polar solvents. What are these forces that act between particles ... 

Chloroform and diethyl ether were among the first substances used as anaesthetics. Both are non-polar substances. 

To summarize, the state of a substance depends on the forces between the particles of that substance. If the forces are very strong, that substance is likely to exist as a solid. If the forces are weaker, that substance will exist as a liquid, or as a gas. The state of a non-polar substance also depends on the size of the molecule. Smaller non-polar molecules are more likely to be gases. Larger non-polar molecules will probably exist as liquids or even solids. Table 11.1 shows the forces discussed in this section ranked in order of strength. 

Zcoii/y is the sum of two Gaussians, the first centered at y = 0 to ensure the correct behavior in the limit of zero density, and the second centered at the rectilinear diameter yT to provide the correct value of residual Helmholtz energy at high density. The temperature dependence of yu is given universal [2], The parameters b and c, which determine the second and third virial coefficients, are given universally for non-polar substances [3]. The pre-exponential factor w has a dominating influence on the vapor pressure. Its temperature dependence requires two substance-specific correction parameters wi and w2. 

The like dissolves like is a useful guide for selecting solvents to use in the extraction, Non-polar substances are usually successfully extracted into non-polar solvents like hexane or methylene chloride. Polar and ionic substances are often extracted with water. 

With V = 100 cm3,VUAjVA — VUBjVB must, therefore, be at least 3.4 so that Tc 300° K which indicates a very appreciable difference in specific cohesion energy, so that partial miscibility is rare in non-polar substances. In most systems of two liquids one of the components is associated. 

Benzene is a colorless, poisonous liquid with a specific odor. It dissolves in organic solvents such as ether, alcohol, acetone and acetic acid. Benzene is also a good solvent for non-polar substances, it is used to dissolve fats, resins, rubber, iodine and sulfur. Its carbon content is high, therefore, when burned, it gives a sooty flame. 

The formation of molecular radical ions by electron transfer reactions between alkali metals and a wide variety of aromatic and other organic compounds in polar solvents is well established. A very large number of radical anions have been prepared by this method and extensive studies of their e.s.r. and optical spectra have been made (Bowers, 1965 Gerson, 1967 Kaiser and Kevan, 1968). In solution the electron transfer reaction will be facilitated by the subsequent solvation of the two ions (or ion pair) by the polar solvent molecules. However, we have observed that similar electron transfer reactions occur readily when alkali metal atoms are deposited on a variety of relatively non polar substances at 77°K in the rotating cryostat. In most cases the parent compound acts as the matrix, though for some radical ions an inert matrix of a non-polar hydrocarbon has been used successfully. It is perhaps surprising that the reactions occur so readily as the energy of solvation of the ions must be quite small in most of these systems as compared with that in the polar liquids. 

Polar molecules are bound more tightly to the stationary phase than non-polar, and thus non-polar molecules are eluted before polar. Typical elution media would be hexane, methylene chloride and ethyl acetate, or mixtures of these. In reverse phase HPLC, however, the opposite applies and the mobile phase is more polar than the stationary phase. Non-polar substances bind more tightly than polar ones, and thus polar compounds are eluted more readily than non-polar ones. Typical solvents would be acetonitrile, methanol, water or mixtures of these. Table 4-5 summarises the essential features of normal and reverse phase HPLC. 

In this way the dielectric constant of a substance can be defined. Due to the electromagnetic nature of light, its transmission is also affected by the dielectric constant of the medium through which it passes. It follows that the refractive index of a substance is a complementary property to the dielectric constant and in some circumstances is a direct function of it. For example for non-polar substances, the... 

For semi-polar substances or mixtures of semi-polar substances and non-polar substances the Lorentz-Lorenz equation applies... 

Liquids with large dielectric constants are sometimes called dipolar liquids (or simply polar liquids). It is interesting to note that these dipolar liquids are good solvents foi ionic crystals (containing electric " poles or charges), and that non polar liquids (benzene, etc.) are good solvents for non-polar substances. 

For non-polar substances the index of refraction may be measured either in the remote infra-red or in the Hertzian region. 

Thus water tends to exclude non-polar substances. When we forcefully disperse a non-polar substance into water then the water must form a cage around the molecule to maximize H-bonds for each water molecule. 

Coupled supercritical CO,-subcritical water systems may facilitate the class-selective extraction of non-polar substances and families of compounds of different polarity by adjusting the temperature of the water. 

When the hydrophobic fraction was analyzed by silica 60 TLC, quite apolar substances were found at the front of the developing solvent (chloroform/methanol/watep=65 25 4). Therefore, we examined whether or not the strain HD-1 produced hydrocarbons from C02. HD-1 cells were collected from 10 liter BM culture. Non-polar substances contained in the chloroform extracts of the disrupted cells were directly analyzed by GC/MS(E1) (Fig. 3a). The characteristic fragmentation patterns and each mass number of the molecular ion peak of these... 

The ability of a substance to dissolve in another substance is called solubility, which can be measured in a number of ways. When a substance does not dissolve in another substance, it is called insoluble. Non-polar substances are often insoluble in polar substances. When both substances are liquids, and the liquids fail to mix, they might be called immiscible, whereas liquids that do mix well are called miscible. 

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