Nonaqueous solvents overview

The influence of interfaeial potentials (diffusion or liquid junction potentials) established at the boundary between two different electrolyte solutions (based on e.g. aqueous and nonaqueous solvents) has been investigated frequently, for a thorough overview see Jakuszewski and Woszezak [68Jak2]. Concerning the usage of absolute and international Volt see preceding chapter. 

In view of the difficulties that accompany the use of a nonaqueous solvent, one may certainly ask why such use is necessary. The answer includes several of the important principles of nonaqueous solvent chemistry that will be elaborated on in this chapter. First, solubilities are different. In some cases, classes of compounds are more soluble in some nonaqueous solvents than they are in water. Second, the strongest acid that can be used in an aqueous solution is H30+. As was illustrated in Chapter 9, any acid that is stronger than H30+ will react with water to produce H30+. In some other solvents, it is possible to routinely work with acids that are stronger than H30+. Third, the strongest base that can exist in aqueous solutions is OH-. Any stronger base will react with water to produce OH-. In some nonaqueous solvents, a base stronger than OH - can exist, so it is possible to carry out certain reactions in such a solvent that cannot be carried out in aqueous solutions. These differences permit synthetic procedures to be carried out in nonaqueous solvents that would be impossible when water is the solvent. As a result, chemistry in nonaqueous solvents is an important area of inorganic chemistry, and this chapter is devoted to the presentation of a brief overview of this area. 

Coordination compounds have been produced by a variety of techniques for at least two centuries. Zeise s salt, K[Pt(C2H4)Cl3], dates from the early 1800s, and Werner s classic syntheses of cobalt complexes were described over a century ago. Synthetic techniques used to prepare coordination compounds range from simply mixing the reactants to employing nonaqueous solvent chemistry. In this section, a brief overview of some types of general synthetic procedures will be presented. In Chapter 21, a survey of the organometallic chemistry of transition metals will be presented, and additional preparative methods for complexes of that type will be described there. 

Our current discussion will, therefore, begin with a brief historical overview of metalloporphyrin electrochemishy and a list of previously utilized nonaqueous solvents and supporting electrolytes, which have been used in porphyrin studies. It will be followed by a general description... 

The area of purely analytical potentiometric titrations is vast and the intent here is to cite a selection of methods and interesting advances in each of the major nonaqueous solvents and which will hopefully indicate a fairly representative overview of the problems and methods encountered in this field. 

Since 1980, several dozen important papers have been published concern-ing investigations on the electrode/electrolyte interface. It is thus possible to give a first overview of the various applications of the techniques. The subjects of various investigations are collected in Table VII, together with the infrared technique which was used and the corresponding references. It can be seen that there is now a wide range of applications, from aqueous to nonaqueous solvents and from adsorbed species on the electrode to species formed in the vicinity of the electrode. It is therefore relevant to select a few examples to illustrate, as well as possible, the appropriateness of each technique. 

Polar organic solvents with electrolytes such as sodium p-toluenesulfonate are compatible with capillary electrophoresis. Background electrolyte need not be an aqueous solution. [P. B. Wright, A. S. Lister, and J. G. Dorsey, Behavior and Use of Nonaqueous Media Without Supporting Electrolyte in Capillary Electrophoresis and Capillary Electrochromatography, Anal. Chem. 1997, 69, 3251 I. E. Valko, H. Siren, and M.-L. Riekkola, Capillary Electrophoresis in Nonaqueous Media An Overview, LCGC 1997, 15, 560.]... 

On the basis of the degree and type of soiling, conservators can choose between localized or complete treatment of the item. Stain removal with solvents with or without additives is the method of choice if soils are localized and the general appearance of the rest of the textile is satisfactory. A systematic overview of methods of stain removal is given in the literature (4). The present discussion focuses on the method of complete immersion in the cleaning medium and on the principles of soil removal associated with this technique. Excellent summaries (5) on detergency in aqueous media exist, but detergency in nonaqueous media is not as well documented. 

As aforementioned (see, e.g., [5-9]), the Chevrel phase cluster compounds paved, on one hand, the way to tailor a new chemical route of synthesis in mild conditions using nonaqueous organic solvents [10-13] as well as in aqueous medium [14], and on the other hand, it provided the necessary ingredients to understand the electronic interaction between the chalcogen and the catalytic metal site [15-18]. Since some recent reviews on the topic of chalcogenides have been done by the author in the last 10 years [6, 8, 9, 19, 20], the present chapter will provide an overview of recent... 

The main problem of mechanistic studies is the broad variety of synthesis systems even within the nonaqueous sol-gel approach, which makes it very difficult to establish generally valid rules and concepts. Every precursor-solvent combination behaves differentiy and slight variations of the synthesis conditions might change the reaction mechanism. Accordingly, it is impossible to exhaustively cover the whole field. Instead, we present selected ex2unples from the recent literature, which, in our opinion, provide a representative overview of the activities in the area of nanoparticle formation mechanisms in nonaqueous environment. 

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