Phenyl group, interaction with

Different types of van der Waals interactions are observed in the complexes. Hydrogen bonds formed between the ammonium Hn atoms and the crown ether O atoms. The strongest Hj jO bonds in complexes of dibenzo-18-crown-6 ether with ammonium cation have a CE of 0.9 eV per bond [7] and bond distances of 1.8 A. The H atoms of the methylene and/or the phenyl group interact with the O atoms of ethers. The weakest interactions observed are between H atoms and phenyl groups as well as between two phenyl groups. In addition, the interactions are not always 1... 

The observed enantioface differentiation in the reduction of the phenyl alkyl ketones was rationalized by postulating a 6-membered ring transition state for hydride transfer (Scheme 10). The transition state leading to the (S)-carbinol has an axial phenyl group interacting sterically with the binaphthoxy oxygen. 

From studies reported in the references in Table 5 (Section 4.04.1.3.1) the dihedral angle between a phenyl and a pyrazole ring in the crystalline state, falls between 4° and 22° when the phenyl group is in the 3- or 4-position. The planar conformation of C-formylpyrazoles (57) and the resonance interaction between them (87) has already been discussed in connection with H NMR (Section 4.04.1.3.3(i)) and IR studies (Section 4.04.1.3.7(iii)). 

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