Dihedral group

Conforma- tion Sym- metry group Dihedral angles ) in Sets of isochronous carbons Calculated relative strain energies in kcal/mole H2) BL3) W ) A8)... 

Properties of the membrane studied included the pressure on all six faces of the simulated volume, displacements of lipid molecules and atomic displacements, deuterium order parameter (S p) as a function of chain position, fluctuations of chain and head group dihedral angles, penetration of water, surface area per lipid molecule, and the lipid self-diffusion coefficient. Interesting re-... 

Compound Conformation Adjacent groups Dihedral anglesf 4> 1 ... 

In order to reduce the number of interactions that need to be evaluated, F-C-C-C and F-C-C-F internal angles were not included explicitly. One could therefore view the potential as a description of CF2-CF2 -CF2-CF2 group dihedral interactions. Explicitly including F-C-C-C and F-C-C-F interactions would most certainly provide an additional level of refinement. Use of this torsional potential with unconstrained fitting of the vdW terms resulted in parameters (Set V, not given in this paper) that did yield and maintain helical conformations, but intermolecular distances were again unsatisfactory. Constrained fitting was required. 

You can detect hydroxyl group transitions hy plotting dihedral an gles versn s lime over the course of th e sim n lation. This is the distance history. Grady investigated the distance history of water... 

From studies reported in the references in Table 5 (Section 4.04.1.3.1) the dihedral angle between a phenyl and a pyrazole ring in the crystalline state, falls between 4° and 22° when the phenyl group is in the 3- or 4-position. The planar conformation of C-formylpyrazoles (57) and the resonance interaction between them (87) has already been discussed in connection with H NMR (Section 4.04.1.3.3(i)) and IR studies (Section 4.04.1.3.7(iii)). 

This type of allylic interaction between the equatorial methyl group and the methylene group adjacent to the nitrogen atom has been recently generali2ed by Johnson and Malhotra (7,7a) as the strain between substituents R and R in the cyclohexenyl-type system shown, as in (11), the dihedral angle between the substituents being 40°. The magnitude of... 

This table gives the displacements for the normal mode corresponding to the imaginary frequency in terms of redundant internal coordinates (several zero-valued coordinates have been eliminated). The most significant values in this list are for the dihedral angles D1 through D6. When we examine the standard orientation, we realize that such motion corresponds to a rotation of the methyl group. 

The Be ring has a chair conformation (dihedral angle 57.6°) with mean B-B distances of 172pm. All 6 B and all 6 N are trigonal planar and the 6-exocyclic NMe2 groups are each twisted at an angle of 65° from the adjacent B3 plane, with... 

Figure 15.6 Various representations of the molecular structure of ryclc-Si2 showing S atoms in three parallel planes. I he idealized point group symmetry is and the mean dihedral angle is 86.1 5.5 . In the crystal the symmetry is slightly distorted to C21, and the central group of 6 S atoms deviate from eoplanarily by 14pm.

Step through the sequence of structures depicting rotation about the C i - C+ bond in 2-methyl-2-butyl cation. Plot energy (vertical axis) vs. CCCC dihedral angle (horizontal axis). What is the preferred conformation, with the ethyl group in plane or perpendicular to the plane ... 

Next come the dihedral angles (or torsions), and the contribution that each makes to the total intramolecular potential energy depends on the local symmetry. We distinguish between torsion where full internal rotation is chemically possible, and torsion where we would not normally expect full rotation. Full rotation about the C-C bond in ethane is normal behaviour at room temperature (although 1 have yet to tell you why), and the two CH3 groups would clearly need a threefold potential, such as... 

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