Physical properties of hydrocarbon salts

The molecular formula, crystalline forms, colour, the results of combustion tests and elemental analysis data are summarized for the isolated hydrocarbon salts [1 2 ], [24 2 ], [28 2 ], [40 2 ] (Okamoto et al., 1990) and [26 2 ] (Takeuchi et al., 1993) in Table 5. 

The IR spectra (KBr disk) of the salts consist of absorptions of both the component cation, [T ], [24 ], [26 ], [28 ] or [40 ], and Kuhn s carbanion [2 ]. The ultraviolet-visible (UV-vis) spectra (DMSO solution) also agree with those of the component cation and anion superimposed, except that [26 2 ] undergoes partial coordination into the covalent form [26-2] in DMSO, as indicated by the presence of only =90% of the theoretical amount of [2 ] at the concentration of =10 m. 

Selected A ax values are listed in Table 6. Eigs 4 and 5 show the observed UV-vis and infrared (IR) spectra of [l 2 ] as a representative. 

Good agreement of the observed limiting equivalent conductances with the predicted values indicates that the component ions exist in DMSO without significant deterioration under argon. It was also shown that [l 2 ] and [24+2 ] are dissociated to more than 99% in DMSO over a concentration range 10- -10- m. 

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Table 5 Some physical properties of hydrocarbon salts prepared from Kuhn s anion [2... 

Amino acid zwitterions are internal salts and therefore have many of the physical properties associated with salts. They have large dipole moments, are soluble in water but insoluble in hydrocarbons, and are crystalline substances with relatively high melting points. In addition, amino acids are amphiprotic they can react either as acids or as bases, depending on the circumstances. In aqueous acid solution, an amino acid zwitterion is a base that accepts a proton to yield a cation in aqueous base solution, the zwitterion is an add that loses a proton to form an anion. Note that it is the carboxylate, -C02-, that acts as the basic site and accepts a proton in acid solution, and it is the ammonium cation, -NH3+, that acts as the acidic site and donates a proton in base solution. 

The physical properties of many macrocyclic polyethers and their salt complexes have been already described. - Dibenzo-18-crown-6 polyether is useful for the preparation of sharpmelting salt complexes. Dicyclohexyl-18-crown-6 polyether has the convenient property of solubilizing sodium and potassium salts in aprotic solvents, as exemplified by the formation of a toluene solution of the potassium hydroxide complex (Note 13). Crystals of potassium permanganate, potassium Lbutoxide, and potassium palladium(II) tetrachloride (PdClj + KCl) can be made to dissolve in liquid aromatic hydrocarbons merely by adding dicyclohexyl-18-crown-6 polyether. The solubilizing power of the saturated macrocyclic polyethers permits ionic reactions to occur in aprotic media. It is expected that this [)ropcrty will find practical use in catalysis, enhancement of... 

Amino arid twiuerions axe internal salts and therefore have nuuty of the physical properties associated urtth salts. They have latge dipol, moments, ttre soluble m water but insoluble in hydrocarbons, and arecrya-... 

Because BLM made of pure lipid or oxidized cholesterol In common salt solutions are nonconducting, the physical properties of BLM are with one exception similar to those of a liquid hydrocarbon layer of equivalent th ckness. The Interfaclal tension of BLM Is less than 5 dynes cm, which Is approximately one order of magnitude lower than that of the hydrocarbon/water Interface. This low Interfaclal tension Is due to the presence of polar groups at the Interface. BLM have negligible permeability for Ions and most polar molecules. Permeability to water Is comparable to that of biological membranes. The permeability to water of Chlorophyll BLM, as determined by an osmotic flew method. Is 50 pm s, which Is in-the range of phospholipid BLM but six times larger than that of oxidized cholesterol BLM. 

Methanol, or as it is termed in full methyl alcohol, with the chemical formula CH3OH is the first of the long series of alcohols. Its molecular weight is 32.04 and it is a neutral, colourless liquid in pure condition having an odour similar to that of ethyl alcohol. Methanol dissolves well with other alcohols, esters, ketones as well as with aromatic hydrocarbons and water. It can be less well mixed with fats and oils. It dissolves a number of organic substances including numerous salts. The most important physical data for methanol are assembled in Tables 3.1 to 3.5. Further data on the physical properties of methanol can be taken from the literature under [3.3-to 3.10]. 

This group of aluminum carboxylates is characterized mainly by its abiUty to gel vegetable oils and hydrocarbons. Again, monocarboxylate, dicarboxylate, and tricarboxylate salts are important. The chemical, physical, and biological properties of the various types of aluminum stearates have been reviewed (29). Other products include aluminum palmitate and aluminum 2-ethylhexanoate (30). 

Four types of organic amines exist, as shown in Table 4.8 primary amines RNHj, secondary R2NH2, tertiary RsNH, and quaternary R4N (Appendix D). The hydrocarbon chain R is usually of length Cg-Cu, commonly a straight aliphatic chain, but branched chains and aromatic parts also occur. In general the amines extract metal complexes in the order tertiary > secondary > primary. Only long-chain tertiary and—to a smaller extent—quarternary amines are used in industrial extraction, because of their suitable physical properties trioctylam-ine (TOA, 8 carbons per chain) and trilauryl amine (TLA, 12 carbons per chain) are the most frequently used. For simplicity we abbreviate all amines by RN, and their salts by RNH L . 

The physical and chemical properties of the X -phosphorins 118 and 120 are comparable to those of phosphonium ylids which are resonance-stabilized by such electron-pulling groups as carbonyl or nitrile substituents Thus they can be viewed as cyclic resonance-stabilized phosphonium ylids 118 b, c, d). As expected, they do not react with carbonyl compounds giving the Wittig olefin products. However, they do react with dilute aqueous acids to form the protonated salts. Similarly, they are attacked at the C-2 or C-4 positions by alkyl-, acyl- or diazo-nium-ions Heating with water results in hydrolytic P—C cleavage, phosphine oxide and the hydrocarbon being formed. 

A number of experimental techniques by measurements of physical properties (interfacial tension, surface tension, osmotic pressure, conductivity, density change) applicable in aqueous systems suffer frequently from insufficient sensitivity at low CMC values in hydrocarbon solvents. Some surfactants in hydrocarbon solvents do not give an identifiable CMC the conventional properties of the hydrocarbon solvent solutions of surfactant compounds can be interpreted as a continuous aggregation from which the apparent aggregation number can be calculated. Other, quite successful, techniques (light scattering, solubilization, fluorescence indicator) were applied to a number of CMCs, e.g., alkylammonium salts, carboxylates, sulfonates and sodium bis(2-ethylhexyl)succinate (AOT) in hydrocarbon solvents, see Table 3.1 (Eicke, 1980 Kertes, 1977 Kertes and Gutman, 1976 Luisi and Straub, 1984 Preston, 1948). 

The difference in ionic conductivity can be attributed to the difference in freedom of the imidazoUum cation. This effect has already been confirmed empirically in our laboratory [11, 12]. For a simple system such as l-ethyl-3-vinylimidazolium TFSl, the ionic conductivity decreased by about four orders upon polymerization. The ionic conductivity of IL polymer brushes having PEO or hydrocarbon chains as spacers between the vinyl group and imidazolium salt are almost the same before and after polymerization. In spite of their rubberlike physical properties, IL polymer brushes had excellent ionic conductivity, around 10 " Scm , at room temperature. Details of the IL polymer brushes are given in Chapter 31. The ionic conductivity of P3 and P4, in which the imidazolium cation is fixed to the main chain, was very low even after salts were added to the matrix. P5 and P6 having the counter anion on the main chain displayed an ionic conductivity fom orders higher than P3 or P4 (about 10 S cm at 50°C). The distance between the vinyl polymer and the imidazolium cation is important for the high ionic conductivity in IL polymers. 

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