Hydrogen bonding, between tetrahedra

Koh, K. N., Araki, K., Komoii, T., Shinkai, S. (1995), Thermotropic liquid-crystal construction through the hydrogen-bonds between a stilbazole calix[4]arene and carboxylic-acids. Tetrahedron Letters, 36, 5191-4. 

Figure 1.15. Left illustration of hydrogen bonding between water molecules in ice the O atom is at the center of a tetrahedron If omed by other O atoms, and the H atoms are along the directions joining the center to the comers of the tetrahedron. The O-H covalent bond distance is a = 1.00 A, while the H-O hydrogen bond distance is = 1.75 A. The relative position of atoms is not given to scale, in order to make it easier to visualize which H atoms are attached by covalent bonds to the O atoms. Right illustration of the stmcture of Ih ice the O atoms sit at the sites of a wurtzite lattice (compare with Fig. 1.5) and the H atoms are along the lines joining O atoms there is one H atom along each such line, and two H atoms are bonded by short covalent bonds to each O atom.

Step b Jt-Facial selectivity may be determined by the stabilizing effect of the H-bond between the benzoate oxygen with the aldehyde hydrogen (see Tetrahedron Lett. 1997, 38, 33). 

In a quantum-chemical MNDO-PM3 level study of the hydration of the Mg2+ cation located in a ditrigonal cavity of the basal surface of clays [99], the most favorable area of Mg2+ cation location was predicted to be in the vicinity of the AIO4 tetrahedron formed by the isomorphic substitution of Si for Al in the silica-oxygen sheet. The authors have showed the important role of the hydrogen bond formation between the water molecules and the oxygen atoms of the silica-oxygen sheet in the Mg-ion hydration. This was confirmed in several MC simulation studies [65, 66]. 

For the compounds with amphoteric properties, the existence of coordination groups Me(OH)4 (tetrahedrons) and Me(OH)g (octahedrons) is characteristic hydroxyl bonds exist between separate groups. Molecular structures are characteristic of the compounds with clearly expressed acidic properties. This means that lattice sites are occupied by molecules bound to each other by hydrogen bonds. Since this leads to the decrease of lattice strength, some acids are liquids under normal conditions, while all the bases and amphoteric hydroxides are solids. 

The isoelectronic molecules CH4, NH3, and H2O (Figure 3-10) illustrate the effect of lone pairs on molecular shape. Methane has four identical bonds between carbon and each of the hydrogens. When the four pairs of electrons are arranged as far from each other as possible, the result is the familiar tetrahedral shape. The tetrahedron, with all H—C — H angles measuring 109.5°, has four identical bonds. 

The leftmost carbon atom in the structure is sp hybridized, and the other two carbon atoms are sp hybridized. The atoms in the molecule are located on a single straight line, with the exception of the three hydrogen atoms on the leftmost carbon atom, which point outward toward three of the vertices of a tetrahedron. There is a cr bond between each pair of bonded atoms. The p and py orbitals on carbon atoms 2 and 3 combine to form two TT orbitals and two rr orbitals only the former are occupied in the ground-state electron configuration. 

A four-component capsule with a structure that conforms to a tetrahedron has been recently described by Venkataraman66 Specifically, triphenylamine ortho-tricarboxylic acid self-assembled via 12 O H-O hydrogen bonds to form a molecular tetrahedron (Fig. 36). The hydroxyl groups of the polyhedron participated in hydrogen bonds with single ethanol molecules embedded within each triangular face of each tetrahedron. The assembly crystallized in the rare cubic crystal system. The ability of the acid to form a tetrahedron was reminiscent of the ability of triphenyl-methanol to form a tetrahedron, which also forms inclusion compounds with solvent guests that occupy voids between the polyhedra.32... 

Pigge, F.C., Ghasedi, F., and Rath, N.P. (1999) A new inclusion host an inclusion complex between a 1,2,5-triarolylbenzene host and a benzene guest stabilized by C-H- -O hydrogen bonds. Tetrahedron Lett. 40, 8045 048. 

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