Naphthalene ring, deformed

It is of interest to note that the barrier to ring inversion in the 1,8-bridged naphthalene (190) (26.3 kJ moF1) is considerably lower than that for tetrahydropyran. This has been attributed to the fact that only the heteroatom is out of the plane imposed on the system by the naphthalene framework (81JCS(P2)741). The transition state for the inversion process is calculated to be planar (Scheme 29) and the barrier to inversion is considered to arise mainly from bond angle deformation. 

Theoretical calculations on 3,4-benzophenanthrene (3) and tetrabenzo-naphthalene (4) indicate that the potential energy of deformation arising from out-of-plane bending and ring-angle distortion is of the same order, but that the combined effect of both is much smaller than either separately. 

Because electron density is a local property, electron density studies of the peptide-like molecules show that the nonspherical part of the deformation density (i.e the P]m parameters of Eq. 8) remain essentially the same for a given atom in the same environment (the peptide residue, a phenyl ring, a methyl group...) [29], The same observation was made for porphyrin ligands [30] and by Brock, Dunitz, and Hirshfeld [37] for naphthalene and anthracene type molecules. All these observations suggest that the multipole parameters are highly transferrable from one atom to a chemically similar atom in different molecules and crystals. A key question is is it possible to determine for each chemical type of a given atom a small set of pseudoatom multipole parameters, and can such parameters be used to calculate electrostatic properties of new molecules To answer this question [29], two accurate but low resolution X-ray data sets (sin 0/Xmax = 0.65 A-1) were... 

SC calculations have subsequently also been carried out on many aromatic systems, such as heterocyclic five- and six-membered rings, on naphthalene and on azulene. For naphthalene and azulene, with 10 n electrons, the orbitals obtained are very similar to those of benzene, with the exception of the two orbitals localized at each of the C atoms which bridge the two rings. These orbitals display a three-way deformation, towards each of the three adjacent carbon atoms. In addition equation (12) shows that for a 10-electron system there are 42 possible spin functions which should be taken into account. But since the SC orbitals are fully optimized, it turns out that the only spin functions which play any significant role in these molecules are those corresponding to the Kekul structures (in the case of naphthalene, structures (3), (4), and (5) in Section 3) and that the contribution of the other 39 structures may be neglected. 

The cyclic dimer was completely converted within 10 min at 300 °C, whereas in the case of the trimer a small part remained unpolymerized even after 30 min at 300 °C. The tetramer exhibits an even lower reactivity. Such lower reactivity is due to a slower initiation of the larger ring monomers. At this point, it should be noted that a mixture of cyclic monomers polymerizes much more rapidly than pure cyclic trimers or tetramers. Solid-state thermal polymerization produces a high-molecular-weight polymer (M > 10 ). Cyclic carbonates derived from o,o -bisphe-nols 43-49 and of cyclic carbonates derived from p,p -bisphenols, such as biphenol-A (50), were polymerized and copolymerized in solution using potassium naphthalene, potassium tert-butoxide or phenyl trimethylsilylether in combination with tris (dimethylamino)sulfonium trimethylsilyldifluoride as initiator [7]. From a practical viewpoint, these polycarbonates, which have high heat-deformation temperatures, may be used for moldings [85]. 

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