Substituents specific

Figure 2.1 provides a quick overview of the basic chemical shift ranges for carbon-bound F, CF2, and CF3 substituents. Specific details... 

Substituents Specific rate constant Solvent (liter mole-1 sec-1) Ea (kcal mole-1) JS (e.u.)... 

Bowden-Wooldridge steric constant -> steric descriptors (O number of atoms in substituent specific positions)... 

As with the three polymeric examples, bipyridine ligands have been incorporated into polypeptides at the chain end, in the backbone, and as attached substituents. Specifically, a bipyridine has been coupled to either the amino or acid terminus of polypeptides to afford biological macroligands. For example, the 4,4 -dicarboxylic acid bipyridine was coupled to two 14-unit o-helices in order to analyze the conformation of the parallel structures.272 A triple-helical synthetic metallo-protein was formed through metal-templated self-assembly of a bipyridine unit with a 15-residue peptide substituted in the presence of metal ions.273... 

Cj building blocks, where is a heterosubstituent other than halogen, are mentioned briefly where appropriate, but are discussed in detail in the sections dealing with these substituents specifically. 

The main difficulties associated with constructing the biaryl moiety as a single atropisomer early in the synthesis lies within the arene substitution pattern. The thermal isomerization barrier for a steganone precursor that carries only three ortho substituents is extremely sensitive to the exact identity of those substituents. Specifically, when one of the three groups (e.g., a formyl moiety) adds only a small amount to the inversion barrier and a second substituent (e.g., a methoxy group) is also relatively small, the barrier to inversion renders the biaryl stereochemically labile even at 0 For example, at least one of... 

For the purpose of characterizing chemicals for designing and selecting training sets for QSAR analyses, a values can be retrieved from tabulations (e.g. Perrin, Dempsey and Serjeant, 1981 Hansch, Leo and Taft, 1991). If several substituents are present on a parent structure, the sum of the corresponding cr values is used. Especially for c>-substituents, specific (rvalues for the given chemical class have to be used. 

Alkyl substituents (specifically the octadecyl ODS form) are the most common bonded groups these convert the surface polar hydroxyl groups to a markedly hydrophobic surface upon which chromatography occurs. Elution is carried out with polar solvents such as water and methanol there is a polarity reversal of the stationary and moving phases compared with conventional liquid chromatography on silica, hence the term reverse-phase HPLC. 

---