Water molecule symmetry properties

Ludwig s (2001) review discusses water clusters and water cluster models. One of the water clusters discussed by Ludwig is the icosahedral cluster developed by Chaplin (1999). A fluctuating network of water molecules, with local icosahedral symmetry, was proposed by Chaplin (1999) it contains, when complete, 280 fully hydrogen-bonded water molecules. This structure allows explanation of a number of the anomalous properties of water, including its temperature-density and pressure-viscosity behaviors, the radial distribution pattern, the change in water properties on supercooling, and the solvation properties of ions, hydrophobic molecules, carbohydrates, and macromolecules (Chaplin, 1999, 2001, 2004). 

Those who applied quantum mechanics to atoms and molecules had a wealth of chemists data at hand well-defined bond properties including dipole moments, index of refractions, and ultraviolet absorption qualities and polarizability as well as well-defined valence properties of atoms in molecules. If one attempted to set up a wave equation for the water molecule, for example, there were 39 independent variables, reducible to 20 by symmetry considerations. But the experimental facts of chemistry implied or required certain properties that made it possible to solve equations by semiempirical methods. "Chemistry could be said to be solving the mathematicians problems and not the other way around," according to Coulson. 148... 

The fact that the product of any two of the four covering operations of the water molecule is again one of the four can be expressed by the statement that the set E, C2,(Jv, and covering operations of an object forms its symmetry group. 

Symmetry Properties of the Hydrogen 1 s Orbitals in the Water Molecule Group Orbitals... 

The symmetry operations of the water molecule are collected in Table 6-3, together with the transformation properties of the sundry orbitals classified under C2V, the point group of water (see Figure 6-9). 

The solvated electron thus formed is no longer centered on the parent atom. To form two distinct entities an asymmetrization occurred either by movement of the I atom from the center or of the electron from the spherical symmetry. The electron e q is now the center of solvation, at first near to, but distinct in its diffusive properties from its parent atom. It is bound by oriented water molecules. This process must have occurred in less than the lifetime of the spectroscopic excited state less than 10 1° sec. Fluorescence is not observed in solutions of I q, showing the short lifetime of the primary excited state. 

The possibility to calculate the anomalous properties of water quantitatively with a simple two step function of the orientations partition function of water molecules gives the possibility to estimate the size of the network of H-bonded molecules in liquid water too. We have to take into account the cooperative mechanism of H-bonds and the preference of C2v symmetry of intermolecular arrangements in... 

Water has C2v symmetry. In the gas phase, the measured O-H bonds are 0.957 A, and the H-O-H angle is 104.5° (12). Liquid water and ice have stmctures controlled by the formation of hydrogen bonds. These bonds make it possible for hydrogen ions to exchange among water molecules on the millisecond to picosecond time scale (13), depending on pH. The extensive and dynamic hydrogen bond networks account for many unusual properties of water and hydrated biomolecules (12). 

As described above, the two vicinal cysteines in Dx, Cys 28 and Cys 29, impose structural constraints in the polypeptide chain fold while the Cys 9-X-X-Cys 12 pattern allows the rubredoxin knuckle to be maintained. As a result, the coordination around the metal in Dx, although geometrically not very different, lacks the pseudo two-fold symmetry and has a different local environment in comparison to Rd. The second coordination spheres of the Dx and Rd centers also show some structural differences. In contrast to Rd, Dx has several polar residues and one internal ordered water molecule, hydrogen bonded to a more exposed water molecule (Figures 20-4 and 20-5B). These differences in the local environment around the metal centers may lead to differences in the electrostatic potentials at the iron site which will contribute to the distinctly observed spectroscopic properties of Dx and Rd [31, 34, 35]. 

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