Reagents structures

The alternative approach is to use the computational equivalent of a chemical reaction, or reaction transform. Here, one does not need to define a common template or to generate sets of clipped reagents. Rather, the library can be enumerated using as input the initial reagent structures and the chemical transforms required to operate upon them. In this... 

A catalytic enantio- and diastereoselective dihydroxylation procedure without the assistance of a directing functional group (like the allylic alcohol group in the Sharpless epox-idation) has also been developed by K.B. Sharpless (E.N. Jacobsen, 1988 H.-L. Kwong, 1990 B.M. Kim, 1990 H. Waldmann, 1992). It uses osmium tetroxide as a catalytic oxidant (as little as 20 ppm to date) and two readily available cinchona alkaloid diastereomeis, namely the 4-chlorobenzoate esters or bulky aryl ethers of dihydroquinine and dihydroquinidine (cf. p. 290% as stereosteering reagents (structures of the Os complexes see R.M. Pearlstein, 1990). The transformation lacks the high asymmetric inductions of the Sharpless epoxidation, but it is broadly applicable and insensitive to air and water. Further improvements are to be expected. 

Vol. 18. Organic Complexing Reagents Structure, Behavior, and Application to Inorganic Analysis. By D. D. Perrin... 

Quantitative extraction of PtIV by ra-octylaniline affords a method of separation from Fe111, Co, Ni11, and Cu11 in hydrochloric acid.306 A similar ion-pairing mechanism accounts for extraction by TOPO305 310 and Alamine 304304 (see Tables 5 and 6 for reagent structures) ... 

Figure 16.9 The O-ECAT reagent structure contains a DOTA chelating group and a terminal aminoxy group for coupling to aldehyde and ketone sites of oxidation within biological molecules.

Chapter 16 - It is shown, that there is principal difference between the description of generally reagents diffusion and the diffusion defining chemical reaction course. The last process is described within the framework of strange (anomalous) diffusion concept and is controled by active (fractal) reaction duration. The exponent a, defining the value of active duration in comparison with real time, is dependent on reagents structure. 

The value Df characterizes reagents (methylbenzoata and heptanole-1) and the final product of reesterification reaction (heptylbenzoate) structure. It is found, that Df variation makes 1,48-1,96. In figure 2 the comparison of value a, calculated according to the equations (9) and (12), as the function of D, is adduced. As it is expected, a increase at Df reduction is observed and also a good correspondence of calculation according to the two mentioned equations. This means, that the value a and, hence, reaction active time f. is defined by reagents structure in the reesterification reaction process. 

Pr, -Bu, Me3SiCH2, neopentyl, 4-F-CeH4, 2-MeO-CeH4 Scheme 8.22. Investigation of substrate and Grignard reagent structure. 

Earlier it was noted that nickel and cobalt could be extracted by carboxylic and sulfonic acids, with nickel being extracted at the lower pH. However, with alkylphosphorus acids, a selectivity reversal is observed, with cobalt being favored under acid conditions. The cobalt-nickel separation factor has been shown to depend upon metal concentration, reagent structure, diluent, temperature, and the presence of a diluent modifier. Thus, with increasing cobalt concentration the color of the extractant phase changes... 

Organic Complexing Reagents Structure, Behavior, and Application to Inorganic... 

The relation between the inter- and intramolecular acts is controlled by the reaction conditions such as type and concentration of the reagents, nature of the solvent, temperature, order in which the reagent are mixed, etc. This problem is discussed in much detail elsewhere 3). In this sub-section, we shall be only concerned with some of the experimental and theoretical studies aimed at revealing a relationship between the reagent structure and ineffective cyclization in the course of curing the epoxyamine compositions. 

Styrene and 1,1-diphenylethene are frequently used as target molecules in investigations of the role of reagent structure on its reactivity toward organic compounds. Low-temperature fluorination with trifluoromethyl hypofluorite gives up to six products.32-33 The Hammett correlation value q was established to be — 2.48 and a mechanism suggested in which spin-paired free-radical pairs arc formed, which are then converted by electron transfer into an ion pair.33... 

The effect of the reagent structure on the fluorination of phenyl-substituted alkenes 6 has been studied in great detail and the higher svn addition observed with trifluoroacetyl hypofluorite in comparison with acetyl hypofluorite explained on the basis of an intermediately formed... 

The Role of Reagent Structure in the Mild Introduction of a Fluorine Atom into Organic Molecules Xenon Difluoride, Cesium Fluoroxysulfate and F-TEDA Case ... 

Derivatizing Reagents for Gas Chromatography Derivatizing Reagent Structure/Formula Notes... 

Reagent Structure tnax p, b rbc Reactive species References... 

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