Subject index thermal stability

Ionic liquids are a class of solvents and they are the subject of keen research interest in chemistry (Freemantle, 1998). Hydrophobic ionic liquids with low melting points (from -30°C to ambient temperature) have been synthesized and investigated, based on 1,3-dialkyl imidazolium cations and hydrophobic anions. Other imidazolium molten salts with hydrophilic anions and thus water-soluble are also of interest. NMR and elemental analysis have characterized the molten salts. Their density, melting point, viscosity, conductivity, refractive index, electrochemical window, thermal stability, and miscibility with water and organic solvents were determined. The influence of the alkyl substituents in 1,2, 3, and 4(5)-positions on the imidazolium cation on these properties has been scrutinized. Viscosities as low as 35 cP (for l-ethyl-3-methylimi-dazolium bis((trifluoromethyl)sulfonyl)amide (bis(triflyl)amide) and trifluoroacetate) and conductivities as high as 9.6 mS/cm were obtained. Photophysical probe studies were carried out to establish more precisely the solvent properties of l-ethyl-3-methyl-imidazolium bis((trifluoromethyl)sulfonyl)amide. The hydrophobic molten salts are promising solvents for electrochemical, photovoltaic, and synthetic applications (Bon-hote et al., 1996). 

Still there are efforts to improve the performance of natural mineral oil-based lubricants by the synthesis of oligomeric hydrocarbons, which has been the subject of important research and development in the petroleum industry for many years and has led to commercialization of a number of synthetic lubricants. These materials are based on the oligomerization of a-olefins such as C6-C20 olefins. Industrial research effort on synthetic lubricants has generally focused on improved viscosity index, thermal and oxidative stability, and a pour point equal to or better than that of the corresponding mineral oil lubricants. 

The G + C index would seem to be correlated with the aptitude for thermophily because the G — C pairs comprise three hydrogen bonds instead of two, as in A-T pairs. Therefore, G + G pairs would be expected to be associated with a greater degree of thermal stability of the DNA, although these correlations remain a subject of debate. For an excellent presentation of the role of G + C in microorganisms as a whole, see the work of Tortora, Funke, and Gase (2003). There also seems to be a strong correlation... 

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