Strain valence angle deformation

An alternative approach to modeling the L-M-L angles is to set the force constants to zero and include nonbonded 1,3-interactions between the ligand atoms. In most force fields, 1,3-interactions are not explicitly included for any atoms, instead they are taken up in the force constants for the valence angle terms. This is an approximation because the 1,3-interactions are most often repulsive and thus the function used to calculate the strain energy arising from valence angle deformation should be asymmetric. It was shown that the nonbonded 1,3-interactions around the metal atom are in many cases a major determinant of the coordination... 

In open-chain compounds, where rearrangement products are more easily obtained, 2-bromo-2,4-dimethyl-3-pentanone gives the a-alkoxyketone as a major product even when the reaction is carried out under aprotic conditions.Consequently two factors seem to be decisive in inhibiting cyclopropanone formation and yielding the a-alkoxyketone even in an aprotic solvent. The first is the degree of substitution, which can play a role in open-chain or cyclic compounds. The second operates only in cyclic systems and is ring strain which can be calculated by force field techniques. This kind of strain can be due to valence angle deformations or to transannular nonbonded interactions or bonded interactions. ... 

We subject a sample of solid polymer material to a sudden deformation process y0, with an elastical stress o0 = Gy0 (G shear modules). The original strain gives rise to an increase of the molecular valency angles and the intermolecular distances. From these molecular deformations an elastic molecular potential A0 arises which in turn causes molecular displacements. These prevail in the direction of the original strain, decreasing the elastic potential A in that neighborhood. We can calculate... 

The three carbon atoms of the cyclopropane ring lie in a plane. Therefore the angle strain is expected to be considerable because each C-C-C valence angle must be deformed 49.5° from the tetrahedral value. It is likely that some relief from the strain associated with the eclipsing of the hydrogens of cyclopropane is achieved by distortion of the H-C-H and H-C-C bond angles ... 

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