Molecular anthracene

Picrates, Many aromatic hydrocarbons (and other classes of organic compounds) form molecular compounds with picric acid, for example, naphthalene picrate CioHg.CgH2(N02)30H. Some picrates, e.g., anthracene picrate, are so unstable as to be decomposed by many, particularly hydroxylic, solvents they therefore cannot be easily recrystaUised. Their preparation may be accomplished in such non-hydroxylic solvents as chloroform, benzene or ether. The picrates of hydrocarbons can be readily separated into their constituents by warming with dilute ammonia solution and filtering (if the hydrocarbon is a solid) through a moist filter paper. The filtrate contains the picric acid as the ammonium salt, and the hydrocarbon is left on the filter paper. 

Acridine is a heterocyclic aromatic compound obtained from coal tar that is used in the syn thesis of dyes The molecular formula of acndine is C13H9N and its ring system is analogous to that of anthracene except that one CH group has been replaced by N The two most stable reso nance structures of acridine are equivalent to each other and both contain a pyndine like struc tural unit Wnte a structural formula for acridine... 

The biological properties of dioxin include an ability to bind to a protein known as the AH (aromatic hydrocarbon) receptor Dioxin IS not a hydrocarbon but it shares a certain structural property with aromatic hydrocarbons Try constructing molecular models of dioxin and anthracene to see these similarities... 

Dyes, Dye Intermediates, and Naphthalene. Several thousand different synthetic dyes are known, having a total worldwide consumption of 298 million kg/yr (see Dyes AND dye intermediates). Many dyes contain some form of sulfonate as —SO H, —SO Na, or —SO2NH2. Acid dyes, solvent dyes, basic dyes, disperse dyes, fiber-reactive dyes, and vat dyes can have one or more sulfonic acid groups incorporated into their molecular stmcture. The raw materials used for the manufacture of dyes are mainly aromatic hydrocarbons (67—74) and include ben2ene, toluene, naphthalene, anthracene, pyrene, phenol (qv), pyridine, and carba2ole. Anthraquinone sulfonic acid is an important dye intermediate and is prepared by sulfonation of anthraquinone using sulfur trioxide and sulfuric acid. 

At pressures of 13 GPa many carbonaceous materials decompose when heated and the carbon eventually turns into diamond. The molecular stmcture of the starting material strongly affects this process. Thus condensed aromatic molecules, such as naphthalene or anthracene, first form graphite even though diamond is the stable form. On the other hand, aUphatic substances such as camphor, paraffin wax, or polyethylene lose hydrogen and condense to diamond via soft, white, soHd intermediates with a rudimentary diamond stmcture (29). 

R. Docherty, K. J. Roberts. Modeling the morphology of molecular crystals Applications to anthracene, biphenyl and B-succinic acid. J Cryst Growth 55 159, 1988. 

Due to the steric requirement of these substituents the formation of a columnar structure with infinite M M interactions is inhibited, and only the association of pairs of molecular units is allowed. The Ni Ni distance is 3.21 A [164]. If the same compound is crystallized in the presence of benzimidazole, the [Ni(dmg-BF2)2]2 dimer units are sandwiched between sheets of benzimidazole molecules due to n-n interactions resulting in an increased Ni Ni separation of 3.358 A [165]. With anthracene the n-n interactions seem to be stronger, because in this case the parent dimer molecule is cleaved. Each monomer now has a conformation of type B (Fig. 32) and is sandwiched by anthracene molecules [166]. Compound 121 has the same configuration [163d]. 

Anthracenes are planar by virtue of the necessity of maintaining aromaticity. When the central ring is reduced, an overall "butterfly" conformation is achieved. For reasons that are not yet understood at the molecular level, this conformation is often associated with central antidepressant activity. 

Midinger and Wilkinson<54> have used flash photolysis and fluorescence quenching by heavy atoms to determine the intersystem crossing efficiencies of anthracene and a number of its derivatives. As discussed in Section 5.2b, heavy atoms present as molecular substituents or in the solvent serve to promote multiplicity forbidden transitions. When anthracene is excited the following processes can occur ... 

The electrodynamic forces proposed for stabilizing jellium provide the principal type of bonding in molecular crystals such as solid methane, rare gas crystals, solid anthracene, and the like. These forces also form the inter-chain bonding of long-chain molecules in polymeric materials (the intra-molecular bonding within the chains is usually covalent). 

There is a rough correlation between the hardnesses and the cohesive energies of molecular crystals as shown by Roberts et al. (1995). These authors studied crystals of 11 pharmaceutical compounds and found a linear correlation between their hardnesses and their cohesive energies. However, the data scatter substantially. The hardnesses range from about 1.0 (aspirin), through 5.0 (sucrose), to 10.0 (anthracene) kg/mm2. 

Clearly, the hardnesses of thermoplastic polymers are not intrinsic. They depend on various extrinsic factors. Only trends can be cited. For example, as the molecular weight in polyethylene materials increases, they become harder. And, as the molecular aromaticity increases, a polymeric material becomes harder. Thus, higher molecular weight anthracene is harder than napthalene and more aromatic Kevlar is harder than polymethacrylate. 

Research in PAH carcinogenesis has made major advances in the past decade. Most notable has been identification of diol epoxide metabolites as the active forms of benzo[a]pyrene, 7,12-dimethylbenz[tf]anthracene, and other carcinogenic PAH. This finding has stimulated enormous research activity and opened the way to determination of the detailed molecular mechanism of action of this important class of carcinogenic molecules. 

Chemical Name 9,10-dimethylbenz[a]anthracene CAS Registry No 56-56-4 Molecular Formula C20H16 Molecular Weight 256.341 Melting Point (°C) ... 

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