Complexation direction

Direct Blue 218 had reported sales of 623 t valued at 4.4 million ia 1987. It is produced from Direct Blue 15 (76) by metallizing and elimination of methyl groups from the methoxide to form the copper complex. Direct Blue 15 (76) is prepared by coupling o-dianisidine [119-90-4] to two moles of H-acid (4-amiQO-5-hydroxy-2,7-naphthalenedisulfonic acid) under alkaline pH conditions. Other important direct blues iaclude Direct Blue 80 (74), (9-dianisidine coupled to two moles of R-acid (3-hydroxy-2,7-naphthalenedisulfonic acid [148-75-4]) followed by metallizing to form a bis copper complex, and Direct Blue 22 (77), an asymmetrical disazo dye, prepared by coupling o-dianisidine to Chicago acid [82-47-3] and 2-naphthol. Direct Blue 75 (78) is an example of a trisazo dye represented as metanilic acid — 1,6-Q.eve s acid — 1,6-Q.eve s acid — (alb) Ai-phenyl J-acid. 

The complex directive effects in radical addihons have been reviewed, and rules for predicting rates and regiochcmistry have been developed [154 755]... 

Thionitrosyl complexes have already been briefly mentioned on p. 453 and have recently been reviewed.They were first made " by reacting azido complexes directly with... 

Anions do not complex directly with EDTA, but methods can be devised for the determination of appropriate anions which involve either (i) adding an excess of a solution containing a cation which reacts with the anion to be determined, and then using EDTA to measure the excess of cation added or (ii) the anion is precipitated with a suitable cation, the precipitate is collected,... 

The chief drawbacks to using the Collins reagent are the nuisance involved in preparing pure dipyridine chromium VI) oxide,6 its hygroscopic nature5 and its propensity to enflame during preparation.2 3 5 The present method avoids these difficulties by simply preparing diehloromethane solutions of the complex directly.7 In... 

Yields in the above reactions can often be improved by the addition of 1 mole of triphenylphosphine directly to the trifluoroacetic acid solution of the reactants immediately before final work-up. It would appear that the triphenylphosphine functions as a scavenger for TTFA released in the metal-metal exchange reaction, thus protecting the final phenol from further electrophilic thallation and/or oxidation. Validation of the metal-metal exchange mechanism was obtained indirectly by isolation and characterization of an ArTlX2/LTTFA complex directly from the reaction mixture. NMR analysis revealed that this complex still possessed an intact aryl-thallium bond, indicating that it was probably the precursor to the transmetallation products, an aryllead tristrifluoroacetate and TTFA. 

Electron-transfer activation. Time-resolved spectroscopy establishes that irradiation of the charge-transfer band (hvCj) of various arene/0s04 complexes directly leads to the contact ion pair. For example, 25-ps laser excitation of the [anthracene, 0s04] charge-transfer complex results in the ion-radical pair instantaneously, as shown in Fig. 14218 (equation 76). 

An appropriate ion-specific electrode was found to provide a convenient, precise and relatively inexpensive method for potentiometry of copper(II) ion in copper-complex azo or formazan dyes. Copper(II) ion in copper phthalocyanine dyes can be quantified after anion exchange. Twelve commercial premetallised dyes evaluated using this technique contained copper(II) ion concentrations in the range 0.007 to 0.2%. Thus many copper-complex direct or reactive dyes are likely to contribute low but possibly significant amounts of ionic copper to textile dyeing effluents [52]. 

The concentration dependence and non-linearity observed in do/pH curves indirectly show that it is not legitimate to ignore complexation. Direct experimental evidence, obtained with radiotracer methods (21,30,31), confirms the importance of complexation in the generation of surface charge do. Thus, we need to add the following equations to Equations 2 and 3, assuming for simplicity that the electrolyte is NaCl ... 

It is possible to write the formation of the 2 1 complex directly from the cation and ligand as follows ... 

On the other hand, the methoxyester results from MeOH attack on coordinated double bond, followed by methoxycarbonylation (Scheme 11). In both cases, the formation of 7r-allylpalladium complexes directs the regio-chemistry of the process. By optimizing the reaction conditions, it has been possible to obtain the unsaturated diester selectively. The latter compound is particularly important, since it can be easily transformed after hydrolysis and hydrogenation into adipic acid [52-54], Selective alkoxy-alkoxycarbonylation of 1,3-dienes has also been achieved [55]. 

Since the conversion of 235 to 233 requires only heating, it is possible to synthesise the vinylketenimine complex directly from the vinylketene merely by extending the reaction time sufficiently.69,87,89 Note that 233.j and 233.k were obtained as 1 1 mixtures of diastereoisomers. The subsequent reactivity of the vinylketenimine complexes,87,89,135,143 particularly their utility in the asymmetric synthesis of quaternary carbon centers,143 has also been investigated, but is beyond the scope of this review. 

Metal-substituted hemoglobin hybrids, [MP, Fe " (H20)P] are particularly attractive for the study of long-range electron transfer within protein complexes. Both photoinitiated and thermally activated electron transfer can be studied by flash excitation of Zn- or Mg-substituted complexes. Direct spectroscopic observation of the charge-separated intermediate, [(MP), Fe " P], unambiguously demonstrates photoinitiated ET, and the time course of this ET process indicates the presence of thermal ET. Replacement of the coordinated H2O in the protein containing the ferric heme with anionic ligands (CN , F , Nj ) dramatically lowers the photoinitiated rate constant, k(, but has a relatively minor effect on the thermal rate, kg. 

It is quite often possible to prepare hydroxypyridinone complexes directly by one-pot synthesis from the appropriate hydroxypyranone, amine, and metal salt 90-92). They can also be prepared by reacting complexes such as P-diketonates with hydroxypyridinones (see e.g., Ce, Mo later). Several maltolate complexes, of stoichiometry ML2, ML3, ML4, or MOL2, have been prepared by electrochemical oxidation of the appropriate metal anode, M — a first-row d-block metal (Ti, V, Cr, Mn, Fe, Co, Ni), In, Zr, or Hf, in a solution of maltol in organic solvent mixtures 92). Preparations of, e.g., manganese(III), vanadium(III), or vanadium(V) complexes generally involve oxidation... 

In the presence of DNA reactions (17) and (18) that generate the excited complex directly or indirectly via reaction (19), become much slower or do not take place, and therefore the ECL disappears. This is due to the fact that the Ru(II) and Ru(III) complexes, physically bound to DNA, are protected by the negatively charged phosphate backbone from the reduction by C02. Thus the ECL titration of the metal complex in the presence of DNA has allowed the determination of the equilibrium constant and binding-site size for association of Ru(phen)3 to DNA [82]. 

The hormone-receptor complex directly increases the activity of an enzyme, usually a protein kinase (Figure 12.4) or a phospholipase (Figure 12.5). 

Two ESI-MS approaches can be taken, namely, direct and indirect analysis of the complexes. Direct methods utilize exclusively ESI-MS to analyze the nature of the non-covalent complexes formed under native conditions in the condensed phase while analyzing the products in the gas phase. Indirect methods utilize biochemical and chromatographic methods for preparing and separating the complexes and ESI-MS as the ancillary detector for the individual products of the non-covalent complex, namely, the small molecules and the protein. 

Questions 84-88 appear to be more complex than the rest. The choices C, D or E are simple true or false answers to the statements. The choice between A and B, however, depends on whether the second statement is an explanation of the first statement. In this book, the questions in this section carry clear directions and even a summary to help you understand how to tackle them. This may not be the case in all board examinations, so practise how to summarise complex directions. 

In molecules with hydroxyl groups, the CH2 unit is selectivity introduced on the side of the double bond syn to the hydroxyl group. This indicates that the reagent is complexed to the hydroxyl group and that the complexation directs the addition. Entries 2, 3 and 4 in Scheme 10.5 illustrates the stereodirective effect of the hydroxyl group. 

Stannylalkynes and RhCl(L)2 2 afford many Rh =C=CR(SnPh3) (L)2 complexes directly, which react with H+ to cleave the SnPh3 group [144]. 

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