Water metal ions

This is my second volume as Editor of this series, and I am pleased to say that all involved in the production of this series are extremely happy with the outcome of my first Volume 54, a thematic issue devoted to Inorganic Reaction Mechanisms. More such thematic issues are in the pipeline the next one (Volume 56) will be devoted to Redox-active Metal Complexes and dedicated to the late Dieter Sellmann, followed by Volume 57 devoted to Relaxometry of Water-Metal Ion Interactions and -edited by Ivano Bertini. 

Starch in plants is accompanied by water, metal ions, lipids, proteins, sterols (such as saponins), and alkaloids (as in such exotic plants as Diascoracea).649 Several of these components can be washed out by the isolation of starch, some of them are extractable with organic solvents, and some are volatized by steam treatment. With the exception of metal ions (preceding article, p. 263), the foregoing components form physical mixtures with starch and do not chemically bond with either amylose or amylopectin. Therefore, one may assume that amylose and amylopectin form inclusion complexes with organic components that are similar to those mentioned in the preceding article. 

FIGURE 17.12. Binding of carboxylate and histidyl groups and water molecules to the two metal ions in the active site of the enzyme D-xylose isomerase (Ref. 45). Note the carboxylate-water-metal ion chelate at the left, and the direct metal-carboxylate bonds to the right. The number of atoms in each closed cycle is shown. 

They are formed in the following chain of events. First, the initial step, a chain initiation, which happens as a result of thermal or photo-induced breakage of a chemical bond in the polymer. This often happens with the help of a catalyst (water, metal ion) in the vicinity of the reaction site, where the initiation step produces a hydrocarbon free radical, R ... 

One of the solvents used in ultrafine pattern processing technology is ultrapure isopropanol (IPA), which is widely used in vapor dryers for drying the electronic devices and liquid crystal display substrates that have been washed with ultrapure water [242]-[244]. At present, the large amount of used IPA—containing impurities such as water, metal ions, and particles—is discarded after use. When using IPA, the following serious problems arise ... 

R. van Eldik, I. Bertini (Eds.), Relaxometry of Water-Metal Ion Interactions, Advances in Inorganic Chemistry, vol. 57, Elsevier, San Diego, 2005 L. Banci, I. Bertini, C. Luchinat, Electron and nuclear relaxation, VCH, Weinheim, 1991. 

Humic and Hydrous Oxide Ligands in Soil and Natural Water Metal-Ion Complexation... 

The specifications and allowed impurity levels of lactide monomer for PLA are defined by the polymerization mechanism and the applied catalyst. PLA is commercially produced by ROP of lactides in bulk. The tin(II)-catalyzed process offers good control over molecular weight and reaction rate provided that it is performed in the absence of impurities such as water, metal ions, lactic acid, or other organic acids. Purification of crude lactides is therefore indispensable for the industrial manufacture of high molecular weight PLA (M > lOOkg/mol). In fact, lactide is the ultimate form of lactic acid, in its dehydrated and purest form. 

In conclusion, the most important quality specifications for lactide monomers are those of free acidity, water, metal ion content, and stereochemical purity. 

The most important humic substances in water are the lower-molecular-mass fulvic acids. These species tend to chelate Fe " ion, producing a yellow material called gelbstoffe (German for yellow stuff), which is responsible for much of the undesirable color found in some water. Metal ions bound with fulvic acid are hard to remove from water and, since iron is a very undesirable water impurity, drastic measures such as destruction of the fulvic acid with chlorine may be required to remove the chelated iron. Figure 3.14 illustrates a typical fulvic acid molecule. 

In C, metal-ion complexation increases water s nucleophilicity by converting it to metal-bound hydroxide ion. That is, the metal-ion increases water s tendency to lose a proton as shown by the values listed in Table 23.1. (The of water is 15.7.) Metal-bound hydroxide ion, while not as good a nucleophile as hydroxide ion, is a better nucleophile than water. Metal ions are important catalysts in living systems because hydroxide ion itself would not be available at physiological pH (7.4). 

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