Naphthacene structure

M.p. 296 C. Accepts an electron from suitable donors forming a radical anion. Used for colorimetric determination of free radical precursors, replacement of Mn02 in aluminium solid electrolytic capacitors, construction of heat-sensitive resistors and ion-specific electrodes and for inducing radical polymerizations. The charge transfer complexes it forms with certain donors behave electrically like metals with anisotropic conductivity. Like tetracyanoethylene it belongs to a class of compounds called rr-acids. tetracyclines An important group of antibiotics isolated from Streptomyces spp., having structures based on a naphthacene skeleton. Tetracycline, the parent compound, has the structure ... 

Figure 12.1.7 The molecular structure of rubrene (5,6,11,12-tetraphenyl-naphthacene).

These are benzo[cjphenanthrene and benz[ajanthracene which, as Hewett (36) noted in 1940, are both phenanthrene derivatives. In contrast, linear structures such as naphthacene are not associated... 

Tetracycline and several related antibiotics (aureomycin = chlorotetracycline, terramycin — oxytetracycline dihydrate) are also obtained from various species of Streptomyces, but are of very different structure, being based on the fused polycyclic arene naphthacene. The presence of five hydroxy substituents (six for terramycin) and an NMe2 group, and possibilities for various conformations and tautomers, complicate the study of their... 

The structures of the radical anion of dibenzo[a,c]naphthacene (135) and the corresponding radical cation were investigated by ESR and proton-ENDOR spectroscopies. ... 

Anthracydines (Figure 8.22) are an important group of antitumor compounds that are characterized by a basic structure of 7,8,9,10-tetrahydro-5,12-naphthacene... 

Thermodynamics. Formation of coke is thermodynamically favorable even at POX conditions. Consider the formation of two compounds that approximate the structure of coke, anthracene (C14H10, a 3-ring polycyclic aromatic compound) and naphthacene (CigHi2, a 4-ring polycyclic aromatic). These compounds can be formed from n-Cie by the following two reactions ... 

Chia and Simmons388 calculated the resonance energies (ER)20 of four mono- and dibenzotetraazapentalenes (Scheme 24). Values are comparable with those of o-condensed aromatic systems (naphthacene, ER = 110 kcal mol-1 chrysene, ER = 116.5 kcal mol-1), and, like these carbocyclic systems, angularly-shaped molecules are more stable than linear ones. HMO calculations of delocalization energies (DE) show that the tetraazapentalene structure 15 is more stable than the tetra-azacyclooctatetraene valence isomer 324 (Scheme 14, Section IV,B,2) whether 324 is planar or tub-shaped. Calculations of electrophilic reactivity (Section IV,C,4,d), electronic spectra (by the PPP method employing all singly excited configurations), and bond orders have been carried out, and they confirm the aromatic nature of these systems. 

Photolysis, in the presence of oxygen, of alkenes containing an ally lie hydrogen atom leads to the formation of hydroperoxides. The sensitized process is more efficient, and often yields photoproducts different in structure from those obtained by nonsensitized photooxidation. Cyclohexadiene and related dienes on photolysis in the presence of oxygen yield the transannular peroxides. Thus, on photosensitized oxidation, a-terpinene (410) is converted into ascaridole (411).435 The equivalent process is not, in general, observed in acyclic dienes. Certain polynuclear aromatic hydrocarbons, such as anthracene and naphthacene and including the heterocycles 5,10-diphenyl-1-... 

A two-dimensional X-ray investigation of the structure of diphenyl-enetetracene (87) has been reported by Bennett and Hanson (1953). The atomic coordinates listed in their paper are consistent with a molecule in which the phenyl groups make angles of + 8° with the naphthacene plane. However, Bennett and Hanson warn that this... 

Based on this mechanism, the distinctions observed between the T-T absorption spectra of the intermediate product and nonphotochromic para-naphthacene-quinone51 with a similar structure were explained by the T-T absorption of the photoinduced ana form of this compound, which is observed after the excitation of a photochromic solution by the laser pulse with a width of 25 ns. However, according to other laser photolysis data for compounds of this type, the intermediate product is a a -spirocomplex,60 which was assumed earlier.5,51... 

Oxytetracy cline] (naphthacene carboxamide) structure determined (1952) by... 

In the work of Hauser and Carnigal [126], which led to revisal of the structures of G-2N and G-2A, condensation using a sulphonylphthalide and the enone 172 (see Scheme 44) followed by air oxidation of the primary adduct in DMF at 100°C were used to construct the benzo[a]naphthacene-8,13-dione 173. 

Naphthacene XV) has five Kekul6 structures and Dewar structures with... 

For the hydrocarbons so far considered, which consist of benzene rings connected linearly, the number of Kekul structures is one more than the number of rings. Thus in benzene it is two, naphthalene three, anthracene four, naphthacene five and dibenzanthracene six. The number of structures with elongated tt bonds, however, increases considerably as the number of benzene rings in the molecule is increased and it is this fact that is responsible for the gradual increase in reactivity with the size of the molecule. 

The reaction between Fe3(CO)i2 and naphthacene lead to a new type of binuclear complex (CieHi2)[Fe2(CO)e] for which structure (XXIII) was proposed 22). The condensed aromatics acridine, phenazine, 4-benz[c]acridine, 5-benzo[a]phenazine, and dibenzo[a,c]phenazine were shown to react with Fe3(CO)ia to give complexes in which an Fe(CO)3 moiety is bound to a terminal ring directly adjacent to the heterocycle ring 22). 

CAS 79-57-2. C22H24N209 2H20. An antibiotic obtained by fermentation from Streptomyces rimosus, an actinomycete. Its chemical structure is that of a modified naphthacene molecule having six asymmetrical centers. It has been synthesized. Properties Dull-yellow crystalline powder ... 

Yang and collaborators have established the structures of the photoadducts obtained by ultra-violet light irradiation of benz-[a]anthracene, (80), benz[b]anthracene (also known as tetracene or naphthacene), (81), and dibenz[a,c]anthracene, (82), with 1,3-cyclo-hexadiene. The products result from a single mode of 4+4 cycloaddition. The fact that none of the alternative isomers which could be formed by addition are observed is rationalised in terms... 

Pentacene. Benzo[i>]naphthacene 2,3,6,7-diben-zoanthracene iin-naphthoanthracene, CnHM mot wt 278,35. C 94.93% H 5,07%. Synthesis from m-xylene or from 4-benzyl-1,3-dimethylbenzene and benzoyl chloride in presence of aluminum chloride or from terephthalyl chloride and o-tolylmagaesium bromide Oar, John, Ber, 62, 940 (1929) 63, 2967 (1930) 64, 981 (1931). Synthesis by reduction of 6,13-pentacenequinone Bruckner etal. Tetrahedron Letters 1960, no. 1,5 Bruckner, Tomas z. Acta Chim. Acad. Sci Hung. 28(4), 405 (196l). Structure Campbell et al, Acta Cryst. 14, 705 (1961). 

Picosecond photon-echo experiments have been used to study delocalized electronic excitation of pentacene dimers in a /)-terphenyl host. The fluorescence spectra and temperature dependence of amorphous anthracene films doped with naphthacene show structural changes in amorphous films. ... 

The anthracene/phenanthrene and n hthacene/chrysene isomeric pairs have similar enthalpies of isomerization, a reflection of the similar slopes of Eqs. 33 and 34. However, while the enthalpy of isomerization of anthracene (2 benz[b]naph-thalene ) to the more stable phenanthrene (3 benz[a]naphthalene ) is -23.4 4.8 kJ mor the same structural rearrangement converts naphthacene (4 benz[b]an-thracene ) into benz[a]anthracene (5) with AWisom = 1.6 10.3 kJ mol . We cannot dismiss this apparent incongruity of enthalpies of isomerization as due only to the large uncertainties of the enthalpies of formation. Compounds (3) and (5) are two members of an homologous series whose correlation with the number of carbons... 

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