Hydrogen bonding ring containing

Hydrogen Bonding Ring Containing Polymers Poly(enamine—Ketones)... 

Enamine carbonyl hydrogen bonding ring containing polymers can be made several ways. In the case of poly(amide enamine) prepared from piperazine no mesogenic character was observed. The new materials reported, synthesized... 

Biodegradable Polymers Release Characteristics of Hydrogen-bonded Ring Containing Polymer Matrices. 15 1243-1247. 

In both Ih and Ic, the hydrogen-bonded systems contain cyclohexane-like buckled hexagonal ring motifs chair form in Ic and boat form in Ih. An important distinction is that in Ic all four hydrogen bonds are equivalent by symmetry. In Ih, the hydrogen bond in the direction of the hexagonal axis can be differentiated from the other three. 

Because carbon usually forms four bonds, it is understood that enough hydrogen atoms are bonded to each carbon to give it four bonds. Rings containing five and six carbons are drawn as a pentagon and a hexagon, respectively. 

The hexagonal polymorph of L-cystine contains hydrogen-bonded layers which consist of 1 (16) hydrogen-bonded ring motifs, connected on one side by the disulfide bridges within the cystine molecules, and on the other by N-H O... 

The crystal structure of an analogous symmetrical nonamer 5 (Fig. 8) showed a helical conformation that is fully consistent with the 2D NMR results (Fig. 4b). The molecule contains a large cavity ( 10 A across) with disordered solvent molecules (water and DMF). None of the three-center hydrogen bonds was disrupted, although NOEs indicated that some of the five-membered hydrogen-bonded rings were more distorted than the six-membered ones. 

The nomenclature provides the number of residues contained in one helical turn the subscript denotes the number of atoms comprising the hydrogen-bonded ring formed between donor and acceptor atoms. 

Seebach also reported on mixed /1-peptides with 6 -amino acids alternating with /S -amino acids which carry their side chains on the a-carbon. Such mixed sequences were initially expected to also display a 14-helix [314] structure however, their behavior proved to be quite different. A new CD pattern with a single peak at about 200 nm was observed and a detailed NMR analysis combined with molecular dynamics simulations suggested a new helix, the 12/10 helix, containing both 10- and 12-membered hydrogen-bonded rings. 

Figure 9 Diol derivatives (7-8) of bicyclo[3.3.1]nonane (6) and vertex assignment in the 3D nets formed by 7 and 8. Note that neither 7 nor 8 forms closed hydrogen-bonded rings all closed paths contain the blue intramolecular link. Moreover, both 7 and 8, although prepared as racemates (rac), crystallize in enantiomerically pure forms (conglomerates).

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