Anthracene ring

Quinones that are based on the anthracene ring system are called anthraqumones Alizarin is one example of an anthraqumone dye... 

Both phenanthrene and anthracene have a tendency to undergo addition reactions under the eonditions involved in eertain eleetrophilic substitutions. For example, in the nitration of anthracene in the presence of hydrochloric acid, an intermediate addition product can be isolated. This is a result of the relatively close balance in resonance stabilization to be regained by elimination (giving an anthracene ring) or addition (resulting in two benzenoid rings). 

The iH—NMR spectra of the recently prepared [2.2](l,4)anthraceno-phanes 36 63> resemble those of the isomeric naphthalenophanes 34. In the anti conformer A, the Ha proton, which lies directly above an anthracene ring, absorbs at much higher field strength than the syn Ha proton. 

Polycyclic aromatic hydrocarbons are moderately reactive as the diene component of Diels-Alder reactions. Anthracene forms adducts with a number of reactive dienophiles. The addition occurs at the center ring. There is no net loss of resonance stabilization, because the anthracene ring (resonance energy = 1.60 eV) is replaced by two benzenoid rings (total resonance energy = 2 x 0.87 = 1.74 eV).48 49... 

Quinones that are based on the anthracene ring system are called anthraquinones. 

Figure 21. Rudimentary electron configurations for BA. For each of the two anthracene rings (ring 1 and ring 2) the molecular orbitals are simply represented by HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital). Electrons are represented by vertical lines. All other terms are defined in the text.

A bistricyclic ethylene with seven-membered central rings, 5,5 -bis-5//-dibenzo[a,d]cy-cloheptenylidene (16), has been found to give two stable steroisomers, one with syn- and the other with awft -folding89. An extreme case of yyw-folding is represented by 9,9, 10,10 -tetrahydrodianthracene (18)90, in which the anthracene rings in a bianthrylidene are bent backward to the extent of permitting double bonds between the 9,9 and 10,10 positions. 

The photocycloaddition of cyclic and acyclic 1,3-alkadienes or furans to aromatic rings has been shown in some cases. Not only symmetrically allowed (4 + 4) photocycloaddition but also (4 + 2) photocycloaddition to benzene, naphthalene, and anthracene rings have been reported. These results are also shown in the following subsections. 

The fluorescence of anthracene in benzene is efficiently quenched by N,N-dimethylaniline and a strong exciplex emission appears in a longer wavelength than the emission of anthracene [382-384], However, the addition product was not obtained at all, except the (4 + 4) anthracene dimer (Scheme 114). In contrast, the addition product and reductive dimerization product of dimethylaniline to the anthracene ring are produced via photoinduced electron transfer, which was first reported by Pac and Davidson [385-387], In the case of V-mcthylaniline, some addition products are obtained both in nonpolar and polar solvents [386-389],... 

As the size of the substituents on the central carbon atoms is increased, the longitudinal (long-axis) and lateral (short-axis) slip of the stacked molecules also increases, until a solid-state arrangement with coplanar anthracene rings that do not overlap is achieved. This arrangement is best exemplified by the well-known 9,10-diphenylanthracene (16) (Fig. 14.11) [30],... 

The first possibility was examined by titrating carboxylic acids 47, 56, and 34 in 4 1 dioxane-water. As seen in Table 7 and Fig. 16, each anthracene ring raises... 

The chirality of tartrates 60 and 61 are confirmed by circular dichroism (CD) spectroscopy <20060L1701>. Multiple bands in the CD spectra of 60 and 61 are due to tartrate dianions inducing CD in the anthracene rings. This is the first reported case of induced circular dichroism (ICD) observed in a chiral macrocycle. 

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