Significant Examples

36 38 39 Ni(II) lodoethane, methanol, hydrazine Hydroquinone Hydroquinone, catechol [86] [88] [89] 

74 Ni(II) Arabinose, glucose, fructose, lactose, sucrose, maltose, maltotriose [183] 

Several authors have also reported the potential use of electropolyme-rized metalloporphyrin films as new electrode materials for anion detection and pH measurements. For example, Daunert et al reported that anion-selective membrane electrodes can be prepared by electropolymerizing aniline-substituted cobalt tetraphenylporphyrin complexes onto a glassy carbon surface. It was shown that the resulting electrodes are highly selective towards the detection of thiocyanate and nitrite anions. The mechanism by which these metalloporphyrin electrode sensors operate is probably related to the well-known axial complexation capability of the central metal cation of the porphyrin towards different kind of anions and bases. The same authors also reported a detection limit of 5 x 10 M for these ion-selective electrodes which have lifetimes of more than 2 months 

Meyerhoff et al have reported the use of a non-metallated porphyrin film as an ion-selective electrode. They have shown that the electropolymerized films offer significant selectivity for the detection of iodide over a wide range of anions. The lifetime of these electrodes was estimated by analyzing some of their characteristics such as sensitivity and detection limits. The effect of pH on the detection of iodide by the film-supported electrodes was also established. For pH values from 3 to 8, there is relatively little effect of the pH on the electrochemical response of the electrodes. At pH values higher than 8, the electrode response is affected by the interference by hydroxide ions. 

More recently, hydroxy-substituted cobalt tetraphenylporphyrins, electro-polymerized onto an optically transparent electrode and adapted onto the tip of an optic fibre were used as sensing materials for the development of optic fibres as pH-sensors . The pH values by this chemically modified optic fibre were monitored by spectrophotometric measurement of the Soret band wavelength for the supported porphyrin. 

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Cellulose acetate Loeb-Sourirajan reverse osmosis membranes were introduced commercially in the 1960s. Since then, many other polymers have been made into asymmetric membranes in attempts to improve membrane properties. In the reverse osmosis area, these attempts have had limited success, the only significant example being Du Font s polyamide membrane. For gas separation and ultrafUtration, a number of membranes with useful properties have been made. However, the early work on asymmetric membranes has spawned numerous other techniques in which a microporous membrane is used as a support to carry another thin, dense separating layer. 

Phosphorite Deposits. Sedimentary phosphorites contain low concentrations of uranium in fine-grained apatite. Uranium of this type is considered an unconventional resource. Significant examples of these uranium ore types include the U.S. deposits in Elorida, where uranium is recovered as a by-product, and the large deposits in North African and Middle Eastern countries (16). 

Trichloromethanesulfenyl chloride is useful in the preparation of various series of sulfur-containing heterocycles. A commercially significant example is the preparation of l,2,4-thiadia2oles. 

One of the historically most significant examples of aromatie nueleophilie substitution is the reaetion of amines with 2,4-dinitrofluorobenzene. This reaetion was used by Sanger to develop a method for identifieation of the N-terminal amino acid in proteins and the proeess opened the way for struetural eharacterization of proteins and other biopolymers. 

In recent years, the rate of information available on the use of ion-exchange resins as reaction catalysts has increased, and the practical application of ion-exchanger catalysis in the field of chemistry has been widely developed. Ion-exchangers are already used in more than twenty types of different chemical reactions. Some of the significant examples of the applications of ion-exchange catalysis are in hydration [1,2], dehydration [3,4], esterification [5,6], alkylation [7], condensation [8-11], and polymerization, and isomerization reactions [12-14]. Cationic resins in form, also used as catalysts in the hydrolysis reactions, and the literature on hydrolysis itself is quite extensive [15-28], Several types of ion exchange catalysts have been used in the hydrolysis of different compounds. Some of these are given in Table 1. 

There are many possibilities for acidic sulphones to react with electrogenerated bases, and give specific functionalization on the a carbon. The first significant example was reported by Baizer58 when reducing sulphone 70 in the presence of oxygen. 

The technique of column switching can increase the versatility of the liquid chromatograph significantly. Examples of the use of column switching will be given in the chapter on applications but, as the technique employs valves similar to those used for sample injection the... 

In addition, electrochemical methods and instruments based on electrochemical phenomena may find direct nses in healing various diseases. The most significant example of a direct dealing metfiod relying on an electrocfiemical phenomenon is defibrillation, a techniqne nsed in reanimation where contraction of the heart muscle is provoked by an electrical pnlse. 

This review will restrict itself to boron-carbon multiple bonding in carbon-rich systems, as encountered in organic chemistry, and leave the clusters of carboranes rich in boron to the proper purview of the inorganic chemist. Insofar as such three-dimensional clusters are considered at all in these review, interest will focus on the carbon-rich carboranes and the effect of ring size and substituents, both on boron and carbon, in determining the point of equilibrium between the cyclic organoborane and the isomeric carborane cluster. A typical significant example would be the potential interconversion of the l,4-dibora-2,5-cyclohexadiene system (7) and the 2,3,4,5-tetracarbahexaborane(6) system (8) as a function of substituents R (Eq. 2). 

The reduction of a high-valent metalla-calix[4]arene in the presence of olefins, dienes, and acetylenes is probably the best, though not unique, synthetic access to the corresponding complexes. A few significant examples have been so far reported. 

Having traversed more than halfway across the periodic table, we now come to the most significant examples. The next three Groups provide the main players for PDT, and zinc is probably the chief amongst these. 

Two inherited human diseases that represent abnormal copper metabolism are Menkes syndrome and Wilson s disease. Menkes syndrome, with symptoms similar to those of copper deficiency, is characterized by a progressive brain disease, abnormally low copper concentrations in liver and other tissues, and diminished ability to transfer copper across the absorptive cells of the intestinal mucosa (USEPA 1980 Aaseth and Norseth 1986). Wilson s disease (hepatolenticular degeneration) is the only significant example of copper toxicity in humans. Wilson s disease is an autosomal recessive disorder that affects normal copper homeostasis and is characterized by excessive... 

Just like any other valence-shell empty orbital, the empty Zr orbital may interact with any proximal electrons, including (i) nonbonding electron pair donors, abbreviated here as n-donors or n-electron pair for simplicity, (ii) 7t-bonds or 7t-electrons, or (iii) a-bonds or o-electrons. Such interactions may be intermolecular or intramolecular. Some of the significant examples are listed in a generalized manner in Scheme 1.3. 

No significant examples of electrophilic attack on. ///-pyrrolizincs were reported since CHEC-II(1996). Nevertheless, treatment of the tricyclic pyrrolizine 53 with aqueous bromine in THF afforded, as expected, the corresponding bromohydrin 54 <1997T4549>. 

As for the modeling of in vitro and in vivo potencies and selectivities, some interesting models were obtained on a subset of representative ligands. In fact, the QSAR analysis of functional activities for this set of compounds, although numerically limited, yields successful correlations [97]. Among these linear correlations, the following equation constitutes a significant example ... 

In heteroaromatic compounds such as 110 atom can be part of the aromatic ring [252, 259- [258] (Scheme 1.48), the nitrogen 262]. The most significant examples... 

The interaction of other transition metal oxides with alkenes has also been studied in detail. Some significant examples are the LRe03 compounds... 

Other, even more significant, examples of Zn(II) complexes with redox-active ligands will be discussed in Chapter 6, Section 5. 

Let us now illustrate some significant examples of the redox propensity of related (but less widely studied61) quinone diimines. As happens for 1,2-dioxolenes, such ligands also exhibit the reversible electron transfer sequence o-benzoquinone diiminejo-benzosemiquinone diimine monoanion/ o-phenylendiamine dianion illustrated in Scheme 4. 

Quenched fluorophores are encapsulated in liposomes and exposed to the inhibitors in the desired concentrations. If leakage of liposomes occurs, fluorescence intensity should increase significantly. Examples for applied markers are (i) self-quenching calcein (<60mM) (ii) HPTS (35mM) with the quencher DPX (50mM) (126,128) and (hi) 8-aminonaphthalene-l,3, 6-trisulfonic acid (ANTS) and DPX. 

Certain ion-radical reactions can be stimnlated by means of direct potential imposition without mediators. In these reactions, the substrate is a depolarizer, and the reactant is a conducting electrolyte. Electrochemical organic synthesis is a well-developed field, and many relevant examples have been provided in all the chapters of this book. Now it is reasonable to give only the significant examples. 

Several solid state structures of RsE (solvent) complexes are known and structural data of significant examples are given in Table XVI. Considerable attention was paid to the structure of the TPFPB salt of the silylated toluenium ion 82 and its... 

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