Bond lengths intramolecular hydrogen bonds

The major structural characteristics of cellulose I, determined in this and other studies, include extended chains stabilized alorig their lengths W two intramolecular hydrogen bonds per glucose residue (0(3)- 0(5) and 0(6)—0(2) ), the arrangement of the chains into sheets stabilized by one intermolecular hydrogen bond per residue (0(3)—0(6)), and the packing of the sheets into a three-dimensional structure marked by a parallel-chain arrai ement. These structural characteristics are illustrated in Fig. 2. 

The phen derivatives (319) and (320) contain intramolecular hydrogen bonds, and have been incorporated into the complexes [Ru(319)(bpy)2] " and [Ru(320)(bpy)2r. Spectroscopic methods and viscosity data have been used to investigate the interactions between these species and calf thymus DNA. It is proposed that binding of [Ru(319)(bpy)2] involves the intercalation of ligand (319) between the base pairs of DNA partial intercalation is proposed for [Ru(320)(bpy)2] . " The length of the spacer in the bridging ligand (321) in [(phen)2Ru(//-321)... 

Upon formahon of the trans adduct of benzaldehyde with TADDOL, the intramolecular hydrogen bond is shortened by 0.128 A, and the acidity of the substrate binding hydroxy funchon is increased. The length of the intermolecular hydrogen bond to the carbonyl group is 1.825 A. 

The effect of molecular size, conjugation length, and competition with ex-cimer formation on ESIPT in conjugated polymers, in which the intramolecularly hydrogen-bonded moieties reside in the main domain, has been examined [204], The polymers were poly(5 -(2 -hydroxy)phenylenebenzobisoxazole (56) and poly(4 -(2 -hydroxy)phenylenebenzobisoxazole (57). A large extent of -rr-elec-tron delocalization is found to inhibit the ESIPT process. Excimer formation is found to be competitive with ESIPT in the polymers studied, whereas molecular size does not inhibit ESIPT. 

The IR study of these peptides in CDCl3 solution at high dilution showed that a much higher content of intramolecularly hydrogen-bonded forms exist in (Ala)4 than in (Val)4 peptides. At higher concentrations, chain length, solvent, and side chain effects are all operative in determining the extent of peptide association in these... 

C2 Z = 8 Dx = 1.457 R = 0.032 for 1,535 intensities. The crystals contain two symmetry-independent molecules, both of which have the C4 conformation, but differ in the orientation of the thio-glycosidic bonds. The torsion angle S-5-C-1-S-1-C-6 is 159° in one molecule and 82° in the other. As in methyl jS-D-ribopyranoside, there are intramolecular hydrogen-bonds between O-2-H and O-4-H. The O-H O direction of the hydrogen bonds is opposite in the two molecules. There are small, but possibly significant, differences in the S-C bond lengths. 

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