7t-Hydrogen bonds

CH/7T hydrogen bonds in organic reactions have been reviewed, including major sections on diastereoface- and enantioface-discriminating reactions.223 g)... 

Figure 4-6. The interactions of (—)-HA with the active site of TcAChE. (a) The hydrogen bonding networks. The water molecules are represented by red balls, (b) The C—H... 7t hydrogen bonds. The distances are given in angstroms. Copy from Ref. 10.

The complex C6H6-HOCH3 is a suitable model for this interaction. In this work, the IPES of the 7T-hydrogen bonding interaction pattern (Fig. 14) was under consideration. 

P. Ottiger, C. Pfaffen, R. Leist, S. Leutwyler, R.A. Bachorz. and W. Klopper, Strong N-H...7T hydrogen bonding in amide-benzene interactions,... 

Peptide X-H...jt interactions are fimctional in stabilization of helix termini, strand ends, strand edges, 8-bulges, and regular turns. Side-chain X-H...7T hydrogen bonds are formed in considerable numbers in a-helices and j8-sheets [205]. The conformational influence of N - H...n and O -in organic molecules and also their role in crystal packing have been established [206,207]. The study on C- interactions has clearly established... 

The 7t scale of solvents (Kamlet-Taft scale) is intended to represent the solute-solvent interactions in the absence of strong forces such as hydrogen-bonding or dipole-dipole interactions. It is based on the n to n absorption of a series of seven solutes (six uitroaromatics, such as 4-uitroanisole, A, A -diethyl-3-nitroaniline, 1-ethyl-4-uitrobeuzeue, etc., aud 4-dimethylamiuobenzophenone) [51-53]. 

The correlation of Snyder s solvent strength e° with molecular dipolarity and polarizability (7t ) and the hydrogen-bond acidity (a) and the hydrogen-bond basicity ((3) solvatochromic parameters for adsorption chromatography can be achieved, although most papers on solvatochromic parameters deal with reversed-phase systems [18]. 

The structure of the 1 1 methanol solvate of olanzapine has been reported, where pairs of olanzapine molecules form a centrosymmetric dimer by means of C—H—-7t interactions [66]. The solvent molecule was linked to the drug substance through O—H-N, N—H O, and C—interactions. In a new polymorph of the 1 1 dioxane solvatomorph of (+)-pinoresinol, the structure was stabilized by O—H O hydrogen bonds between the compound and the solvent [67], Two new polymorphs of 2-cyano-3-[4-(/Y,jV-diethylamino)-phenyl]prop-2-enethioamide and its acetonitrile solvatomorph have been characterized [68], Although crystallization of the title compound was conducted out of a number of solvents, only the acetonitrile solvatomorph could be formed. 

FIGURE 1.10 Comparison of enantiomer separations of DNB-Leu on quinine (QN) based and 0-9-(terf-butylcarbamoyl)quinine (tBuCQN) based CSPs. 1, ionic interaction 2, jt-7T-interaction 3, hydrogen bonding 4, steric interaction. Experimental conditions Eluent, methanol-0.1 M ammonium acetate (80 20 v/v) (pHa = 6.0) flowrate, 1 mLmin temperature, 25°C column dimension, 150 x 4 mm ID detection, UV 250 nm. Selector loadings, 0.37 and 0.30 mmol g l for QN- and tBuCQN-based CSPs, respectively. (Reproduced from A. Mandl et ah, J. Chromatogr. A, 858 1 (1999). With permission.)... 

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