Ethanol—continued solvent properties

Liquid acetic acid is a hydrophilic (polar) protic solvent, similar to ethanol and water. With a moderate relative static permittivity (dielectric constant) of 6.2, it can dissolve not only polar compounds such as inorganic salts and sugars, but also non-polar compounds such as oils and elements such as sulfur and iodine. It readily mixes with other polar and non-polar solvents such as water, chloroform, and hexane. With higher alkanes (starting with octane) acetic acid is not completely miscible anymore, and its miscibility continues to decline with longer n-alkanes. This dissolving property and miscibility of acetic acid makes it a widely used industrial chemical. 

Sass C, Walter J, Bennett GN (1993) Isolation of mutants of Clostridium acetobutylicum ATCC 824. Curr Microbiol 26 151-154 Sauer U, Diirre P (1995) Differential induction of genes related to solvent formation during the shift from acidogenesis to solventogenesis in continuous culture of Clostridium acetobutylicum. FEMS Microbiol Lett 125 115-120 Schneider Z, Larsen EG, Jacobson G, Johnson BC, Pawelkiewicz J (1970) Purification and properties of glycerol dehydrase. J Biol Chem 245 3388-3396 Schoutens GH, Groot WJ (1985) Economic feasibility of the production of isopropanol-butanol-ethanol fuels from whey permeate. Process Biochem 20 117-121... 

Sol-gel synthesis is the process of formation of porous, three-dimensional, integrated solid network (gel) of either discrete particles or network potymers from the conversion of monomers into stable suspension of colloidal solid particles or pol miers (sol) in a continuous liquid phase. Most popular precursors for the synthesis of colloids are metal alkoxides and alkoxysilanes. Tetramethoxysilane (TMOS) and Tetraethoxysilane (TEOS) are commonly used alkojq silanes, which form silica gel. The remarkable property of these silanes is that they readity react with water in the presence of shorter chain alcohol such as ethanol and ammonia to form monodispersed silica particles [7]. The size of silica particles formed is between 50 and 200 nm and depends on the silica ester used, type of alcohol, and molar ratios of water and alkoxysilane [32]. In this process, alcohol acts as a homogenizing solvent between alkoxides and water as both are immiscible but can be easily dissolved in alcohol. With the presence of this homogenizing agent, hydrolysis can be facilitated [33] due to the complete miscibility. However, aluminates borates and titanates often mixed with TEOS or TMOS are commonly used in sol-gel process. The hydrolysis of alkoxysilane proceeds according to Stober s process (Fig. 18.6). 

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