Organic structural relations

Beilstein and Gmelin are the world s largest factual databases in chemistiy. Beil-stein contains facts and structures relating to organic chemistry, whereas Gmelin provides information on inorganic, coordination, and organomctallic compounds. 

Death domain (DD) superfamily consists of structurally related homotypic interaction motifs of approximately 90 amino acids. The motifs are organized in six antiparallel amphipathic a-helices, the so-called DD fold. The four members of the super family are the death domain (DD), the death effector domain (DED), the caspase activation and recruitment domain (CARD), and the Pyrin domain. All are important mediators for the assembly of caspase activating complexes. 

Cyclophanes or 7r-spherands have played a central role in the development of supramolecular chemistry forming an important class of organic host molecules for the inclusion of metal ions or organic molecules via n-n interactions. Particular examples are provided by their applications in synthesis [80], in the development of molecular sensors [81], and the development of cavities adequate for molecular reactions with possible applications in catalysis [82]. The classical organic synthesis of cyclophanes can be quite complex [83], so that the preparation of structurally related molecules via coordination or organometallic chemistry might be an interesting alternative. 

Several dozens of aldolases have been identified so far in nature [23,24], and many of these enzymes are commercially available at a scale sufficient for preparative applications. Enzyme catalysis is more attractive for the synthesis and modification of biologically relevant classes of organic compounds that are typically complex, multifunctional, and water soluble. Typical examples are those structurally related to amino acids [5-10] or carbohydrates [25-28], which are difficult to prepare and to handle by conventional methods of chemical synthesis and mandate the laborious manipulation of protective groups. 

The contributions of QMs to the toxicities of the food additive BHT and structurally related alkylphenols in rats and mice have been investigated extensively over the past 25 years. This work has generated considerable insight into the relationships between toxicity and the metabolic formation and reactivity of these electrophiles. Most studies have focused on liver and lung damage is primarily observed in these organs due,... 

Thus far we have used the word chlorophyll as if this term related to a unique chemical species. In actuality there are a number of structurally related molecules present in photosynthetic organisms which are collectively referred to as chlorophyll. The general chlorophyll structure is ... 

It is the purpose of the series to review the field of organic nitro chemistry in its broadest sense by including structurally related classes of compounds such as nitroamines, nitrates, nitrones, and nitrile oxides. It is intended that the contributors, who are active investigators in various facets of the field, will provide a concise presentation of recent advances that have generated a renaissance in nitro chemistry research. 

Alcohol The family name of a group of structurally related organic chemicals. It is also applied specifically to one member of that family - ethanol, or ethyl alcohol -the psychoactive ingredient of alcoholic drinks. 

Bulk NLO studies on luminescent /uc- ReI(CO)3(a-diimine) + complexes by Yam and co-workers note SHG from surfactant derivatives such as (54) and (55) deposited in Langmuir-Blodgett (LB) thin films.110-112 For example, the 532 nm SHG from LB films of the stilbazole derivative (55) is ca. 50% more intense than that from films of the structurally related purely organic salt traiw-.lV-methyl-4-[2-(4-octadecyloxyphenyl)ethenyl]pyridinium iodide.112... 

Acylpyrazolones (24) also form neutral /3-diketonate-type complexes suitable for extraction of a range of metals into organic solvents and have been considered171 as alternatives to LIX 54 for use in ammoniacal leach circuits. Although they are stronger extractants than LIX 54,4,172 the low solubility of their metal complexes has limited their usefulness in Cu recovery.171 The structurally related diazopyrazolones (25) have pHi/2 values, ca. 3.7, and their chemical stability on contact with ammoniacal feeds meets the requirements of the flowsheet outlined above, but their very intense colors may restrict their use as commercial extractants.173,174 The bulk of the arylazo... 

Disordered carbons usually exhibit a multiscale organization (structure, microtexture, texture)4. Structurally, they are made of more or less distorted polyaromatic layers, nanometric in size. The spatial association or the layers, from the nanometric to the micrometric scales, gives rise to different microtextures (lamellar, porous, concentric, fibrous, etc.) forming the carbons skeleton4. The multiscale organization is the fingerprint of the kind of precursor and of the formation conditions (temperature, pressure, strains, time, etc.) met either in laboratory experiments or in Nature, and is directly related with numerous properties. 

Growth and diet are subject to seasonal changes. The presence (or absence) and relative concentrations of secondary metabolites in the extracts of organisms are factors which chemists should document along with observations made during collection. Often, in preliminary experiments guided by bioassay, mixtures, rather than individual compounds, are tested. Association of a certain activity with structurally related compounds may serve as a lead for further tests, but should not be considered definitive. 

The presence in molluscs of molecules structurally related to typical dietary metabolites could be ascribed either to selective accumulation of minor compounds acquired through the diet, or to an in vivo chemical transformation of major metabolites acquired from the prey. However, all reports on this topic have to be carefully evaluated before drawing hurried conclusions. In particular, interaction among molecules from different organs could favor formation of artifacts when the secondary metabolites are extracted from the whole mollusc and not from individual dissected tissues. Only some cases, where the ability of the molluscs to modify dietary metabolites seems to be well supported, are reported in this chapter. 

Except for very electron-rich donors that yield stable, persistent radical cations, the ox values are not generally available.64 Thus the cation radicals for most organic donors are too reactive to allow the measurement of their reversible oxidation potentials in either aqueous (or most organic) solvents by the standard techniques.65 This problem is partially alleviated by the measurement of the irreversible anodic peak potentials E that are readily obtained from the linear sweep or cyclic voltammograms (CV). Since the values of E contain contributions from kinetic terms, comparison with the values of the thermodynamic E is necessarily restricted to a series of structurally related donors,66 i.e.,... 

Vijverberg, H.P.M., G.S.F. Ruigt, and J.V.D. Bercken. 1982. Structure-related effects of pyrethroid insecticides on the lateral-line sense organ and on peripheral nerves of the clawed frog, Xenopus laevis. Pestic. Biochem. Physiol. 18 315-324. 

An alternative approach, which is usual among physical organic chemists, involves a comparison of changes of thermodynamic quantities for structurally-related reaction series. Such an approach, for which the term extrathermodynamic is widely used (Leffler and Grunwald, 1963), will be adapted here in an appropriate form to the interpretation of chain-length effects on cyclisation rates and equilibria. The experimental basis is provided by cyclisation reactions for which either 0AS+- or 0AS -data are available. 

The logarithm for the capacity factor correlates well with known log P values obtained by the shake flask method. In practice, the k values are determined isocratically from 70 to 30% organic mobile phase and then extrapolated to 0%. Prior to determining the log P for an unknown compound, a set of structurally related molecules (standards) are analyzed to construct a correlation model between the logarithm of the retention factor and known log P values. The process is then repeated for the test compounds and their log P values determined from the mathematical relationship established for the standard compounds. 

Geometry of molecules and ions, structural isomerism of simple organic molecules relation of properties to structure... 

In a further application of MI-SPE, theophylline could be separated from the structurally related caffeine by combining the specific extraction with pulsed elution, resulting in sharp baseline-separated peaks, which on the other hand was not possible when a theophylline imprinted polymer was used as stationary phase for HPLC. A detection limit of 120 ng mb1 was obtained, corresponding to a mass detection limit of only 2.4 ng [45]. This combination of techniques was also used for the determination of nicotine in tobacco. Nicotine is the main alkaloid in tobacco and is the focus of intensive HPLC or GC analyses due to its health risk to active and passive consumers. However, HPLC- and GC-techniques are time-consuming as well as expensive, due to the necessary pre-purification steps required because the sample matrices typically contain many other organic compounds besides nicotine. However, a simple pre-concentration step based on MI-SPE did allow faster determination of nicotine in tobacco samples. Mullett et al. obtained a detection limit of 1.8 jig ml 1 and a mass detection limit of 8.45 ng [95]. All these examples demonstrate the high potential of MI-SPE to become a broadly applicable sample pre-purification tool. 

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