Pyrolysis of naphthalene

Fullerenes can also be obtained by pyrolysis of hydrocarbons, preferably aromatics. The first example was the pyrolysis of naphthalene at 1000 °C in an argon stream [58, 59], The naphthalene skeleton is a monomer of the Cjq structure. FuUerenes are formed by dehydrogenative coupUng reactions. Primary reaction products are polynaphthyls with up to seven naphthalene moieties joined together. FuU dehydrogenation leads to both Cjq as well as C7Q in yields less than 0.5%. As side products, hydrofuUerenes, for example CjqHjj, have also been observed by mass spectrometry. Next to naphthalene, the bowl-shaped corannulene and benzo[k]fluoranthene were... 

Howsam and Jones, 1998). For example, the pyrolysis of naphthalene can yield a range of HMW species such as perylene and benzofluoranthenes, possibly as a result of cyclodehydrogenation of the binaphthyls (Howsam and Jones, 1998). This may be particularly important for compounds that are deposited on the walls of open fireplaces along with soot particulates close to the hot zone of the flame. 

Figure 13.4 Condensation products from the pyrolysis of naphthalene...

For a pitch from the pyrolysis of naphthalene, heptameric and octameric naphthalene condensation products have been postulated as model mesogens the corresponding molecular weights are 878/876 and 1006/1008 (Figure 13.4). 

The molecular weight of isotropic pitch and mesophase pitch differ especially in the width of their distributions. Figure 13.6 shows the molecular weight distribution of isotropic and mesophase pitch from the pyrolysis of naphthalene. The mesophase pitch displays a broader molecular weight distribution and, in addition, the maximum of the distribution curve is found at higher molecular weights than for isotropic pitch. 

Sources of Raw Materials. Coal tar results from the pyrolysis of coal (qv) and is obtained chiefly as a by-product in the manufacture of coke for the steel industry (see Coal, carbonization). Products recovered from the fractional distillation of coal tar have been the traditional organic raw material for the dye industry. Among the most important are ben2ene (qv), toluene (qv), xylene naphthalene (qv), anthracene, acenaphthene, pyrene, pyridine (qv), carba2ole, phenol (qv), and cresol (see also Alkylphenols Anthraquinone Xylenes and ethylbenzenes). 

Several attempts to make this compound by pyrolysis of 2-azidO-3-nitro-naphthalene failed (ref. 35). 

The pyrolysis of vinylidene chloride produced a range of chlorinated aromatic compounds including polychlorinated benzenes, styrenes, and naphthalenes (Yasahura and Morita 1988), and a series of chlorinated acids including chlorobenzoic acids has been identified in emissions from a municipal incinerator (Mowrer and Nordin 1987). 

A number of basic studies in the area of donor solvent liquefaction have been reported (2 -9). Franz (10J reported on the interaction of a subbituminous coal with deuterium-labelled tetra-lin, Cronauer, et al. (11) examined the interaction of deuterium-labelled Tetralin with coal model compounds and Benjamin, et al. (12) examined the pyrolysis of Tetralin-l-13C and the formation of tetralin from naphthalene with and without vitrinite and hydrogen. Other related studies have been conducted on the thermal stability of Tetralin, 1,2-dihydronaphthalene, cis-oecalin and 2-methylin-dene (13,14). 

The fact that most alkylated benzenes show the same tendency to soot is also consistent with a mechanism that requires the presence of phenyl radicals, concentrations of acetylene that arise from the pyrolysis of the ring, and the formation of a fused-ring structure. As mentioned, acetylene is a major pyrolysis product of benzene and all alkylated aromatics. The observation that 1-methylnaphthalene is one of the most prolific sooting compounds is likely explained by the immediate presence of the naphthalene radical during pyrolysis (see Fig. 8.23). 

Pyrolysis of bis(2-ethylhexyl) phthalate in the presence of polyvinyl chloride at 600 °C produced the following compounds methylindene, naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, biphenyl, dimethylnaphthalene, acenaphthene, fluorene, methylacenaphthene, methylfluorene, phenanthrene, anthracene, methylphenanthrene, methylanthracene, methylpyrene or fluoranthene, and 17 unidentified compounds (Bove and Dalven, 1984). 

Pyrolysis of diethyl phthalate in a flow reactor at 700 °C yielded the following products ethanol, ethylene, benzene, naphthalene, phthalic anhydride, and 2-phenylnaphthalene (Bove and Arrigo, 1985). 

Alder-Rickert cleavage has not been widely used for cycloproparene synthesis, since the preparation of the precursors is often tedious, except for the simple cases like 7,7-difluorobenzocyclopropene (21). The approach offers, however, decisive advantages in special situations. If the Alder-Rickert cleavage is carried out under flash-vacuum pyrolysis conditions, the products may be isolated under neutral conditions and at low temperature. Thus the synthesis of the highly reactive li/-cyclopropa[a]naphthalene (56) by pyrolysis of 68 has been achieved by this approach. Several other approaches to 56 failed. 

Wynberg and Bantjes studied the pyrolysis of thiophene at 800°-850° by mass spectrometry they established the presence of isomeric dithienyls, benzo[6]thiophene, and traces of naphthalene, isomeric phenylthiophenes, and thienothiophenes, besides unreacted thiophene and carbon disulfide. 

In a study of the formation and reactions of arynes at high temperatures. Fields and Meyerson plyrolyzed a thiophene solution of phthalic anhydride at 690° by mass spectrometry and gas chromatography they found benzene, naphthalene, benzo[b]thiophene, phenylthiophenes, bithienyls, thienothiophene 1, and naphthothiophene in the pyrolysis products. Pyrolysis of thiophene itself produced benzo-[Z lthiophene, thienothiophene 1, phenylthiophene, and bithienyl. The... 

Vapor phase pyrolysis of 2-aminobiphenyl in chloroform at 350°C produces carbazole,as does heating at 500-800°C in a high-frequency glow discharge at 25-34 A small amount (11%) of carbazole 280 was formed during the reaction of 281 with copper-potassium carbonate and 1-iodo-naphthalene in nitrobenzene. ... 

The formation of reactive carbenes from alkylidene Meldrum s acids has also been observed. Thus pyrolysis of 1-indanylidene Meldrum s acid at 640 °C gave the corresponding carbene which further rearranged to benzofulvene and naphthalene (Scheme 12) <1998JA8315>. Similarly, EVP of 9-fluorenylidene Meldrum s acid at 1100°C provided a mixture of phenanthrene and biphenylene <1996TL6819>. 

Naphthalene is produced from coal tar or petroleum. It is made from petroleum by dealkylation of methylnaphthalenes in the presence of hydrogen at high temperature and pressure. Petroleum was a major source of naphthalene until the 1980s, but now most naphthalene is produced from coal tar. The pyrolysis of bituminous coal produces coke and coke oven gases. Naphthalene is condensed by cooling the coke gas and then separated from the gas. Naphthalene production in the United States is slightly greater than 100,000 tons annually. 

The presence of zeolite catalysts increases the amount of gaseous hydrocarbons produced during pyrolysis but decreases the amount of pyrolysis oil. Further, significant quantities of coke were formed on the surface of the catalysts in the course of pyrolysis. The catalysts reduced the yield of e.g., as styrene and cumene, in favor of naphthalene. The zeolite catalysts, especially Y-Zeolite, were found to be very effective in removing volatile organo bromine compounds. However, they were less effective in removing antimony bromide from the highly volatile products of pyrolysis (133). 

There is a difficulty with the mechanism of Scheme 3 in that the fragmentation of a triplet diradical should conserve spin, yet neither triplet Me2Si nor triplet tetraphenyl-naphthalene have been detected. The diradical pathway for the photofragmentation of silanorbornadienes confirms an earlier proposal by Barton and coworkers52. There is always the possibility that diradical intermediates such as the singlet and triplet 13 S and 13 T could function as silylenoids. Thus, the assumption that products from pyrolysis of 7-silanorbornadienes are formed from free silylenes must be treated with caution. 

These results are consistent with the reaction pathways shown in Figure 5. The major neat pyrolysis pathway, illustrated in Figure 5a, requires two molar equivalents of BPA for the formation of one mole each of toluene, aniline, and carbon-rich products (CRP) which include the observed benzalaniline. The network for thermolysis in tetralin is a combination of the neat pyrolysis pathway (Figure 5a) and a pathway wherein tetralin and BPA react to one mole each of toluene and aniline, and 0.5 molar equivalents of naphthalene. 

Steric hindrance in aryl-substituted borazines depends on o-substitu-tion of the aryl groups. Significant results concerning the reaction of primary arylamines with trihaloboranes, have recently been discussed in detail 89>9°). While pyrolysis of aniline-trihaloboranes or o-toluidine-trihaloboranes yields the corresponding B-trichloroborazines, the base-promoted dehydrohalogenation of the latter results in the formation of a l,3-diazaro-2,4-dibora-naphthalene compound besides a minor amount of borazine. 

To confirm reaction scheme (4) for the formation of naphthalene and biphenyl, phthalic anhydride was allowed to react with benzene-dx (Fields and Meyerson, 1966c). Barring an appreciable isotope effect, two-thirds of the naphthalene should contain a deuterium atom and one-third only protium. Biphenyl arises in two ways insertion of benzyne into a C—H bond of benzene and pyrolysis of benzene. Biphenyl from benzyne insertion should form with retention of the deuterium atom biphenyl from benzene pyrolysis should—again ignoring any isotope effect—be d0, dlt and dz on the statistical basis of losing two, one, or zero deuterium atoms from a total of twelve protiums and deuteriums in the over-all reaction of two benzene molecules. The amount of biphenyl-... 

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