Dihedral angles Subject

Cyclodecene is the smallest cycloalkene, which can accommodate a trans double bond without significant deformation of bond angles and/or dihedral angles. The strain energies and structures of smaller fraws-cycloalkenes have been the subjects of considerable research over the years. 

The latter case, however, differs from the two preceding in two major points (a) in the dithiole ring, the dihedral angle C-S-S-C is very small, if not zero, whereas it is near 90° in noncyclic disulfides108 (b) in the dithiole ring, there is an appreciable aromatic character, although the importance of the ring current remains subject to speculation. 

In particular, for the hydrogen atom, it was recognized that the confinements by elliptical cones and by dihedral angles were pending. Section 5.1 in the Preview of Ref. [9] formulated the problem of the hydrogen atom confined by a family of elliptical cones identified in its Eqs. (123 and 124), with the boundary condition that the wavefunctions vanish in such cones, Eqs. (125 and 126). The corresponding solution [8] is the subject of Section 3.3. 

G calculations on 2,3,7,8-tetrachlorooxanthrene have been carried out and the authors found that a near planar structure is favored for this compound <88JOC547l). Thianthrene has been the subject of many theoretical studies. Molecular mechanics calculations predict an inversion barrier of 4.6 kcal mol by the MM method <85JA5323), and a dihedral angle of 150° or 125° by the semiempirical PM3 calculational method <930M77S) or hy the 4-31G basis set <90JST(204)4i), respectively. 

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