Organic Ions in Solution

In spite of the relatively recent start of mass spectrometric ion-cluster studies, considerable information has been accumulated which promises to be of importance in a number of fields such as radiation chemistry of gases, ionic processes in the troposphere and ionosphere, gas discharges, and the study of inorganic and organic ions in solutions of polar and nonpolar solvents. 

Capillary Electrophoresis. Capillary electrophoresis (ce) is an analytical technique that can achieve rapid high resolution separation of water-soluble components present in small sample volumes. The separations are generally based on the principle of electrically driven ions in solution. Selectivity can be varied by the alteration of pH, ionic strength, electrolyte composition, or by incorporation of additives. Typical examples of additives include organic solvents, surfactants (qv), and complexation agents (see Chelating agents). 

Organic acid Some glasses are more prone to attack by organic acids than by other acids with a lower pH value. These acids form complex ions in solution which increases the glass solubility. Many vitreous enamels contain lead oxide and are susceptible to attack by organic acids. Consequently their corrosion resistance is assessed by exposure to acetic or citric acidsThe test temperature is always stipulated because a rise of 10°C can double the rate of reaction between glass and acid. 

I hope therefore that, in the not too distant future, an expert on the modeling of organic reactions in solution will investigate the dediazoniation of aromatic or aliphatic diazonium ions in water. 

For ease of use and wavelength accuracies of 1-2 nm, organic materials or inorganic ions in solution have been recommended as standards (Table II). However, these must be used carefully because (a) the peak maxima are matrix dependent, (b) narrow Instrumental bandpasses are necessary, (c) impurities may affect peak location, and (d) the peak wavelength values have generally not been certified (11). 

As noted above, adsorption isotherms are largely derived empirically and give no information on the types of adsorption that may be involved. Scrivner and colleagues39 have developed an adsorption model for montmorillonite clay that can predict the exchange of binary and ternary ions in solution (two and three ions in the chemical system). This model would be more relevant for modeling the behavior of heavy metals that actively participate in ion-exchange reactions than for organics, in which physical adsorption is more important. 

Encapsulation of a metal ion by a saturated organic framework is expected to lead to robust metal derivatives which are stable over a wide pH range and thus, for example, inhibit the hydrolysis which is characteristic of certain metal ions in aqueous solution. In this manner, the non-hydrolytic coordination chemistry of these ions in solution becomes accessible. Similarly, the redox chemistry of such encapsulated ions is of special interest, since there exists the prospect that the saturated organic shell might insulate the metal ion to a greater or lesser degree from the surrounding medium and hence markedly influence electron transfer reactions. 

The terms reactivity and stability are amongst the most used words in chemistry. In relation to organic cations, they are evidently determined to a large extent by the electrical properties of these species, by which we mean, amongst other features, the charge-distribution and the reduction potential of the ion-in-solution. 

It is mysterious to me why thiolates look so good in organic chemistry in solution. I think that is something we have to understand better, but it appears not to be an intrinsic property of thiolate ions. Thiolates will not displace each other, they are not good leaving groups, and so on, in the gas phase. Their reactivity is exactly what one would predict. 

Selective ion electrodes (SIE). Selective ion electrodes are essentially variants of the well-known pH meter. They are membrane indicator types of electrodes in which a potential is developed across a membrane in the presence of the ion the size of the potential is related to the concentration and hence can be used to quantitatively detect and measure the species. However, instead of a glass membrane, as in the pH meter, the membranes consist of organics that are immersible in water. For example, anion-sensitive electrodes use a solution of an anion exchange resin in an organic solvent the liquid can be held in the form of a gel, for example, in polyvinyl chloride. The ion reacts with the organic membrane, setting up an equilibrium between the free ion in solution and the ion bound to the membrane, generating a potential difference, which is measured. 

H. Taube, Electron Transfer Reactions of Complex Ions in Solution, Academic Press, New York 1970. >C.K. Ingold, Structure and Mechanism in Organic Chemistry, 2. Aufl. S. 406-417, Cornell University... 

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