Bond angle and conformation

Structure parameters. For a single compound, the structure parameters include the proportion of atoms and their connectivity, the geometric and energetic parameters of bonds, angles, and conformation, and the electronic parameters of electron distribution and polarization. For multicomponent systems of solutions, microstmctural material, and composite material, the additional structure parameters include the proportion of the various components, and the relations of their phases as solutions, colloids, or composite solids. 

Calculation of the bond angles and conformation of the cyclic phosphates by minimization of ring and eclipsing strain leads to bond angles.closely in accord... 

Figure 3. Two alternate methods of describing an a-D-glucose residue using the variable virtual bond method. The bond length, bond angle, and conformation angle for atom 05 are shown as ts, 6s, s-...

Ashida, T., Tsunogae, Y., Tanaka, I., and Yamane, T. Peptide chain structure parameters, bond angles and conformational angles from the Cambridge Structural Database. Acta Cryst. B43, 212-218 (1987). 

Theoretical attempts to relate dimensions of polymers to chemical structure were pioneered by Flory (2). Statistical macromolecular size in solution can be modeled from first principles by considering the number and length of bonds along with valence bond angles and conformational restrictions. Excluded volume, segmental interactions, specific intramolecular interactions, and chain solvation contribute to dimensions. 

At Its most basic level separating the total strain of a structure into its components is a qualita tive exercise For example a computer drawn model of the eclipsed conformation of butane using ideal bond angles and bond distances (Figure 3 8) reveals that two pairs of hydrogens are separated by a distance of only 175 pm a value considerably smaller than the sum of their van der Waals radii (2 X 120 pm = 240 pm) Thus this conformation is destabilized not only by the torsional strain associ ated with its eclipsed bonds but also by van der Waals strain... 

Molecular mechanics (also known diS force-field calculations) is a method for the calculation of conformational geometries. It is used to calculate bond angles and distances, as well as total potential energies, for each conformation of a molecule. Steric enthalpy can be calculated as well. Molecular orbital calculations (p. 34) can also give such information, but molecular mechanics is generally easier, cheaper (requires less computer time), and/or more accurate. In MO calculations, positions of the nuclei of the atoms are assumed, and the wave equations take account only of... 

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