Puckered planes

While ice Ih ice II by hydrogen bonding diagonally across the hexagons of the puckered planes perpendicular to the Ih c axis, ice Ih ice III by hydrogen... 

Figure 31 A schematic representation of the 1 -2-3 structure, or the 90 K superconducting compound, Ba2YCu3Oe+x. Note the Cu(l) square-planar chains and the Cu(2) puckered planes in the structure.

Fig. 65. The corundum structure. A-B and C-D c-axis pairs share a common octahedral face, C-B" and D-A basal-plane near neighbors share a common octahedral edge, and there are A"-B and C-A cation-anion-cation couplings between adjacent basal, puckered planes of cations.

GaOCl. The structure of GaOCl (and the isostructural AlOCl, AlOBr, and AlOI) consists ot layers of tetrahedral Ga03Cl groups (Ga—0, 1-91 A, Ga—Cl, 2-22 A) which are linked as shown in Fig. 10.16. Each 0 atom is common to three tetrahedra, the unshared vertices of which are occupied by the Cl atoms. In a given row of tetrahedra these Cl atoms lie alternately to one side or the other of the (puckered) plane of the A1 and 0 atoms. 

Diamond has two basic crystal stmctures, one with a cubic symmetry (more common and stable) and the other with a hexagonal symmetry (rare but well established, found in nature as the mineral lonsdaleite). The close-packed layers, 111 for cubic and 100 for hexagonal, are identical. The cubic structure can be visualized as stacking of puckered planes of six-membered saturated carbon rmgs man EO EO sequence along (111) direction, referred to as 3C diamond (Fig. 1). All ofthe rings exhibit the chair... 

The gas-phase structure of 1,3-dithietane 1-oxide (189) has been determined from its microwave spectrum and the spectra of eight isotopic modifications192. The ring is puckered, the angle between the two CSC planes being 39.3° with the oxygen equatorial. 

In graphite each carbon atom is bound to three others in the same plane and here the assumption of inversion of a puckered layer is improbable, because of the number of atoms involved. A probable structure is one in which each carbon atom forms two single bonds and one double bond with other atoms. These three bonds should lie in a plane, with angles 109°28 and 125°16,l which are not far from 120°. Two single bonds and a double bond should be nearly as stable as four single bonds (in diamond), and the stability would be increased by the resonance terms arising from the shift of the double bond from one atom to another. But this problem and the closely related problem of the structure of aromatic nuclei demand a detailed discussion, perhaps along the lines indicated, before they can be considered to be solved. 

There are two schools of thought as to the structure of graphite oxide. Ortho or meta ether linkages have been postulated to enforce a puckering of planes (Al), whereas a keto-enol tautomerism was suggested to keep the carbon layers planar (C3). 

The iron of unoxygenated myoglobin lies 0.03 nm (0.3 A) outside the plane of the heme ring, toward His F8. The heme therefore puckers slightly. When O2 occupies the sixth coordination position, the iron moves to within 0.01 nm (0.1 A) of the plane of the heme ring. Oxygenation of myoglobin thus is accompanied by motion of the iron, of His F8, and of residues linked to His F8. 

The six-membered ring of a hexose such as a-glucose takes on a puckered structure. A molecular plane can be defined that passes through the midpoints of all the bonds of the ring. Bonds to non-ring atoms are either perpendicular to this plane (shown in green) or roughly parallel to the plane (shown in brown). 

Central NPg almost planar, but 93 other N and P atoms puckered out of this plane... 

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