Hydrogen bonds crystal structure

Zacharias, D. E. and Desiraju, G. R. (1993). Solid-state supramolecular assembly via C—H O hydrogen bonds - crystal structures of the complexes... 

The alditol crystal structures are conformationally homogeneous. The cocrystallization of different conformers of the same molecule is not common, but sufficient examples are known, especially in hydrogen-bonded crystal structures, for it to be a phenomenon with which crystallographers are familiar. It occurs when there is a population of conformers in solution, all of which have similar energies. A classical example is that of 2,3-dimethyl-2,3-butanediol (pinacol)... 

Katrusiak, A. (1998). Modelling hydrogen-bonded crystal structures beyond resolution of diffraction methods. Pol. J. Chem. 72, 449-459. 

Much of the impetus for the study of hydrogen bonded network structures of 24 and bipy or other linear N-donor ligands has come from the desire to perform time-resolved crystallographic studies of photoactive guest species embedded within the network as a guest [58,62,63]. Embedding a photoactive species within a network structure effectively dilutes it in the solid state. The advantages of this include improved uniformity of illumination of the crystal, less photons are... 

The effect of hydrogen bonds on the physical properties of crystals is shown in a striking way by oxalic acid. This substance exists in two anhydrous crystal forms. 1 One of these, the a form, contains layers of molecules held together by hydrogen bonds, the structure of a layer... 

Not all clathrates are hydrates. Other well-known examples have host lattices formed from hydrogen bonded aggregates of hydroquinone, phenol, and similar organic compounds. Non-hydrogen bonded host structures are also known. One example is a cyclotriphosphazene. (C6H402PN). that traps molecules such as benzene in tunnels in the crystal.2 In addition, coordination polymers are formed by ambidentate ligands, such as CN and SCN, which coordinate to metal ions at both ends (Chapter 12). Perhaps the best known of this type of compound is the series of Ni(CN)2NHj M compounds, where M may be benzene, thiophene, furon. pyrrole, aniline, or phenol. 

He first graduated, in 1928, at the University of Sheffield, where he became a lecturer in chemistry, with research interests chiefly in the electrochemical field. In 1946 he moved to J. M. Robertson s laboratory at Glasgow, and his interests then began to turn towards crystal-structure analysis by x-rays and neutrons. He has applied Robertson s methods mainly to the study of hydrogen-bonded crystals and his preoccupation with this topic continues. 

Presence of native starch crystals. In plant materials, starch exists as semicrystalline, granular entities. Starch molecules, both amy-lose and amy lopectin, with their many intermo-lecular hydrogen bonds, give structure to the starch granule (Zobel, 1988). The crystalline regions formed by this intermolecular hydrogen bonding are somewhat resistant to enzyme hydrolysis and need to be broken prior to enzyme treatments. 

Figure 8.48 The symmetry unique portion of the infinite co-crystal hydrogen-bonded chain structure of [U02C12(H20)3]16-([15] crown-5) 16.76...

Fig. 11. A view of the ribbon-like hydrogen-bonded super-structure of the 6-hydroxy- ra ,S -3-hexenoic acid 107 in the crystal.

Similar shortening of the C-N bond and lengthening of the C=0 bond is found when the structures of acetamide [376, 377], fluoroacetamide [299], and thioacetamide [204] in the hydrogen-bonded crystals are compared with ab-initio molecular orbital calculations for the isolated molecule, as shown in Thble 5.4. 

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