Bases direct attachment

A coordination compound, or complex, is formed when a Lewis base (ligand) is attached to a Lewis acid (acceptor) by means of a lone-pair of electrons. Where the ligand is composed of a number of atoms, the one which is directly attached to the acceptor is called the donor atom . This type of bonding has already been discussed (p. 198) and is exemplified by the addition compounds formed by the trihalides of the elements of Group 13 (p. 237) it is also the basis of much of the chemistry of the... 

The nature of the substituent directly attached to the N-atom influences the properties (basicity, reduction potential, etc.) of the C = N function more than the substituents at the carbon atom. For example, it was found that Ir-dipho-sphine catalysts that are very active for N-aryl imines are deactivated rapidly when applied for aliphatic imines [7], or that titanocene-based catalysts are active only for N-alkyl imines but not for N-aryl imines [8, 20, 21]. Oximes and other C = N-X compounds show even more pronounced differences in reactivity. 

Acyl nitroso compounds (3, Scheme 7.2) contain a nitroso group (-N=0) directly attached to a carbonyl carbon. Oxidation of an N-acyl hydroxylamine derivative provides the most direct method for the preparation of acyl C-nitroso compounds [10]. Treatment of hydroxamic acids, N-hydroxy carbamates or N-hydroxyureas with sodium periodate or tetra-alkyl ammonium periodate salts results in the formation of the corresponding acyl nitroso species (Scheme 7.2) [11-14]. Other oxidants including the Dess-Martin periodinane and both ruthenium (II) and iridium (I) based species efficiently convert N-acyl hydroxylamines to the corresponding acyl nitroso compounds [15-18]. The Swern oxidation also provides a useful alternative procedure for the oxidative preparation of acyl nitroso species [19]. Horseradish peroxidase (HRP) catalyzed oxidation of N-hydroxyurea with hydrogen peroxide forms an acyl nitroso species, which can be trapped with 1, 3-cyclohexanone, giving evidence of the formation of these species with enzymatic oxidants [20]. 

The silicon substrate constitutes a very interesting support for facilitating the integration in microelectronic devices. The electrochemical and electroanalytical fields can gain remarkable benefits from the silicon-based miniaturization devices, especially if arrays of metal electrodes can be fabricated. An understanding of the electrochemical properties of CNTs directly attached to silicon is thus essential for their potential application in developing silicon-based electrochemical or (bio)electrochemical... 

Sapsford etal. (2001) examined microarray-based antibody-antigen binding kinetics in real time to determine the effect of spot size. Capture antibodies were immobilized in an array pattern onto silver-clad microscope slides. Antimouse IgG was directly attached to the surface or attached via neutravidin capture of the biotinylated antibody. Cy5-labeled mouse IgG capture was monitored based upon the signal generated from the excitation of an evanescent wave guide (slide) with a 635-nm laser source detection was achieved by a charge-coupled device (CCD) camera system. Both static and flow-through conditions were employed. 

Naphthenic acids are based on saturated single or inulticyclic condensed ring structures, The low molecular weight naphthenic acids contain alkylated cyclopentane carboxylic acids, with smaller amounts of cyclohexane derivatives occurring, The carboxyl group is usually attached to a side chain rather than directly attached to the cycloalkane, The simplest naphthenic... 

Compounds with two or more silicon atoms directly attached to one another, subdivided into sections based first on the number of silicon atoms and then on the carbon functionality attached to the silicon atoms. Frequently, but not exclusively, the main photochemical behavior involves homolysis of a silicon-silicon bond yielding silyl radicals, but in some cases silylenes result directly from the photochemistry. The resulting compounds are frequently the products of a molecular rearrangement. 

Despite the fact that the quaternization event occurs on a nitrogen atom that is not directly attached to the resin, we were gratified to observe that the products 6 are indeed released by base treatment. Release of the desired compounds from the resin was carried out in the development stages with various proportions of TEA or DIEA in DCM. We later observed that release could be carried out in several different solvents using one of a variety of organic and inorganic bases.13 For single compound... 

Another possibility for a rigorous comparison of the reactivities of the individual electroactive groups is the comparison (7,110) of potential ranges (based on the application of the Hammett equations, cf. section 3.1) of half-wave potentials of benzene derivatives bearing an electroactive group either in the side-chain or directly attached to the benzene ring, and further one single substituent in the m- or -position (Fig. 30). 

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