Complementary intermolecular hydrogen bonding

Fig. 2.25 Motif of complementary intermolecular hydrogen bonding of two-component gelators.

TEM image of ethyl acetate gel formed by a 1 1 mixture of 78 and 5-(2-ethyl-hexyl)barbituric acid is shown in Fig. 2.24. It exhibits the gathering of numerous fibrous twisted aggregates. Constricted ribbons will be formed by twisting of the molecular tape, built up through complementary intermolecular hydrogen bonding. 

The motif of complementary intermolecular hydrogen bonding is shown in Fig. 2.25. The molecular arrays based on complementary intermolecular hydrogen bonding is formed, but the branched alkyl chains of the two components are randomly folded and bent, in contrast to the extended alkyl chains of cocrystals. Besides 76+77 and 78+79, some other two-component gelators have been report-... 

Fig. 5 Complementary intermolecular hydrogen bonding formed by compounds 20 and 21.

DNA forms a complementary structure of two helically oriented polynucleotide chains (fig. 1.13). The polar sugar and phosphate groups are situated on the surface, where they can interact with water the nitrogenous bases from the two chains form intermolecular hydrogen bonds in the core of the structure. 

Melamines and barbiturates or cyanurates are complementary with respect to their ability to form hydrogen bonds. Three intermolecular hydrogen bonds between adjacent molecules may lead to hydrogen-bonded polymeric or oligomeric structures in the crystalline state.278... 

With the combination of the covalent bond forming capability of the metal ion and the inherent capability of the ligand for formation of complementary hydrogen bonds, a diversity of H-bonded structures has been obtained, including intramolecular hydrogen-bonded monomers (148), intermolecular hydrogen-bonded dimers, tetramers (149-151) and polymers having one-dimensional chain (152), two-... 

DNA is a right-handed, double-stranded helix, in which the bases essentially occupy the interior of the helix, whereas the phosphodiester backbone (sugar-phosphate backbone) more or less comprises the exterior. The bases on the individnal strands form intermolecular hydrogen bonds with each other (the complementary Watson-Crick base pairs). An adenine base on one strand interacts specifically with a thymine base on the other, forming two hydrogen bonds and an A-T base pair while a G-C base pair contains three hydrogen bonds. These interactions possess a specificity that is pivotal to both DNA repfication and transcription (see Figure 2). 

Fig. 4 Ar,AT-bisGauroyl)-fran5-l,2-cydohexylamine 20 and intermolecular hydrogen bonding motif between self-complementary cyclohexylbisamide units in gel aggregates gelator 21 with mesogenic cyanobiphenyloxy units and the mesomorphic compoimds 22 and 23 giving room-temperature liquid crystals...

Unlike ribonucleic acids, which are single-strand polymers, DNA form doublestrand helices, a sort of twisted ladder, consisting of two complementary chains. This complementarity occurs through intermolecular hydrogen bonding between two pairs of bases, between the adenosine of one strand and the thymidine of another, and likewise between cytidine and guanosine. 

The present volume contains 13 chapters written by experts from 11 countries, and treats topics that were not covered, or that are complementary to topics covered in Volume 1. They include chapters on mass spectra and NMR, two chapters on photochemistry complementing an earlier chapter on synthetic application of the photochemistry of dienes and polyenes. Two chapters deal with intermolecular cyclization and with cycloadditions, and complement a chapter in Volume 1 on intramolecular cyclization, while the chapter on reactions of dienes in water and hydrogen-bonding environments deals partially with cycloaddition in unusual media and complements the earlier chapter on reactions under pressure. The chapters on nucleophiliic and electrophilic additions complements the earlier chapter on radical addition. The chapter on reduction complements the earlier ones on oxidation. Chapters on organometallic complexes, synthetic applications and rearrangement of dienes and polyenes are additional topics discussed. 

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