Four and More Torsion Angles

When the same method is applied to conformational interconversion involving four torsion angles, the visualization problems become much more severe. One method, described in Chapter 2, Section 2.6.5, is to use a normal stereo plot for three of the four dimensions, and to represent the distance along the fourth coordinate by circles 

Richter, R., Kaiser, J., Sieler, J., Hartung, H., Peter, C., Acta Cryst. 1977, B33, 1887 Prelog, V., Kung, W., Tbmljenovic, T., Helv. Chim. Acta 1962, 45, 1352 Shenhav, H., Schaeffer, R., Cryst. Struct. Comm. 1981, 10, 1181 Sim, G.A., Acta Cryst. 1990, B46, 676 

Aigami, K., Inamoto, Y., J. Chem. Soc., Perkin II1979, 172 

Gerber, P.R., Gubernator, K., Muller, K., Helv. Chim. Acta 1988, 71, 1429 

In 1929 Pauling proposed as the second of his Principles Determining the Structures of Complex Ionic Crystals [1], that a cation-anion bond could be characterized by the oxidation state (atomic valence) of its cation divided by its coordination number. He showed that the total amount of this quantity, usually now called the Pauling Bond Strength, received by the anion was approximately equal to the anion oxidation state. He called this the Electrostatic Valence Principle, but it is now commonly referred to as Pauling s Second Rule. 

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