- Synthesis of Benzofluoranthenes from 1-Halobenzophenanthrenes by Flash Vacuum Pyrolysis
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1-Chlorobenzophenanthrene 23 was prepared via the oxidative photochemical cyclisation of suitably halogenated stilbenes and was cyclised to benzofluoranthene 2 by flash vacuum pyrolysis.
- Plater, M. John
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- From phenylenes to acenes: Flash vacuum pyrolytic isomerization of angular [3]phenylene to benzo[ghi]fluoranthene
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The flash vacuum pyrolysis of angular [3]phenylene and bis(2-ethynylphenyl)ethyne produces benzo[ghi]fluoranthene and chrysene, respectively.
- Matzger, Adam J.,Vollhardt, K. Peter C.
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- Thermolysis of benzo[c]phenanthrene: Conversion of an alternant C18H12 PAH into non-alternant C18H10 PAHs
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The product composition of the pyrolysates obtained upon thermolysis of the alternant C18H12 PAH benzo[c]phenanthrene (1) is markedly pressure dependent. At 0.1-0.5 Torr (N2 carrier gas, 1050-1150°C) 1 is converted into the non-alternant C18H10PAH's cyclopenta[cd]pyrene (4) and benzo[ghi]fluoranthene (5) which have been identified as abundant combustion effluents and are associated with fullerene formation.
- Sarobe,Jenneskens,Wiersum
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- Use of external radical sources in flash vacuum pyrolysis to facilitate cyclodehydrogenation reactions in polycyclic aromatic hydrocarbons
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A new process to facilitate the cyclodehydrogenation of polycyclic aromatic hydrocarbons (PAHs) in flash vacuum pyrolysis (FVP) using an external radical source is described. Using hexanes as an external radical source the conversion of various PAHs to their cyclodehydrogenated products is vastly increased. Various other volatile organic compounds were also examined to determine their ability to act as external radical sources in FVP.
- Amick, Aaron W.,Martin, Sara E.
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p. 1338 - 1343
(2014/11/08)
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- Intramolecular aryl-aryl coupling of fluoroarenes through Al 2O3-mediated HF elimination
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A strategy for effective intramolecular aryl-aryl coupling of fluoroarenes through Al2O3-mediated HF elimination is reported. It is demonstrated that the C-F bond, which is widely believed to be the most passive functionality in organic chemistry, can be reconsidered as a useful functional group allowing very effective C-C bond formation. The solid-state strategy presented in this study opens the possibility for facile syntheses of insoluble extended polycyclic aromatic hydrocarbons.
- Amsharov, K.Yu.,Merz
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experimental part
p. 5445 - 5448
(2012/08/27)
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- Facile bucky-bowl synthesis by regiospecific cove-region closure by Hf elimination
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Building bowls: An effective intramolecular aryl-aryl coupling is the key step in rational fullerene synthesis and in synthesis of extended buckybowl structures. Such a process can be embodied very efficiently through quantitative HF elimination on active Al2O3. The process is characterized by an unprecedentedly high chemoselectivity and regiospecificity. Copyright
- Amsharov, K. Yu.,Kabdulov,Jansen, Martin
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supporting information; experimental part
p. 4594 - 4597
(2012/06/30)
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- Highly efficient fluorine-promoted intramolecular condensation of benzo[c]phenanthrene: A new prospective on direct fullerene synthesis
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Various functional groups have been tested as alternative promoters of the intramolecular condensation of benzo-[c]phenanthrene under flash vacuum pyrolysis conditions. Methyl and fluorine functionalization were found to be promising approaches. Unexpectedly high selectivity was observed in the cyclization of fluorinated benzo[c]phenanthrenes. The mechanism for the condensation reaction and the advantages of fluorine as a promoter for the rational synthesis of fullerenes are discussed. Wiley-VCH Verlag GmbH & Co. KGaA.
- Amsharov, Konstantin Yu.,Kabdulov, Mikhail A.,Jansen, Martin
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p. 6328 - 6335
(2011/03/19)
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- Aryl-aryl bond formation by flash vacuum pyrolysis of benzannulated thiopyrans
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(Chemical Equation Presented) In contrast to fully unsaturated 7-membered ring sulfur heterocycles (thiepines), some of which extrude sulfur and give the ring-contracted hydrocarbon even at room temperature in solution, benzannulated thiopyrans (6-membere
- Amick, Aaron W.,Wakamiya, Atsushi,Scott, Lawrence T.
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p. 5119 - 5122
(2008/12/20)
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- Interconversions of aryl radicals by 1,4-shifts of hydrogen atoms. A synthesis of benzo[a]corannulene
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Aryl radicals generated ortho to aryl substituents by flash vacuum pyrolysis (FVP) of the corresponding aryl chlorides are shown to be capable of transferring hydrogen atoms between the ortho and ortho' positions (1,4-shifts of hydrogen atoms). In the examples described here, the rearranged aryl radicals are trapped by subsequent radical cyclization reactions. For example, FVP of 2-(ochlorophenyl)-benzo[c]phenanthrene gives 1-phenylbenzo[ghi]fluoranthene as the major product by homolysis of the C-CI bond, 1,4-shift of a hydrogen atom out of the sterically congested cove region to the radical center, cyclization of the rearranged radical, and rearomatization of the molecule by loss of the other cove region hydrogen. In a control experiment run under the same conditions, FVP of 2-phenylbenzo[c]phenanthrene, which lacks a radical precursor, gave primarily recovered starting material. When the FVP was repeated using 2-(2,6-dichlorophenyl)benzo[c]phenanthrene as the starting material, benzo[a]corannulene was obtained as the major product, presumably by the same cascade of events to produce 1-(o-chlorophenyl)benzo[ghi]-fluoranthene, which then suffers a second radical cyclization spontaneously under the high-temperature conditions to give the geodesic polyarene.
- Peng, Lingqing,Scott, Lawrence T.
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p. 16518 - 16521
(2007/10/03)
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- Isomerization of linear to angular [3]phenylene and PAHs under flash vacuum pyrolysis conditions
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(matrix presented) Flash vacuum pyrolysis (FVP) of linear [3]phenylene affords its angular counterpart and the same mixture of polycyclic aromatic hydrocarbon isomers as that observed on FVP of angular [3]phenylene. A mechanism, supported by a 13C labeling study, is proposed to explain these results.
- Dosa, Peter I.,Schleifenbaum, Andreas,Vollhardt, K. Peter C.
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p. 1017 - 1020
(2007/10/03)
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- Evolution of products in the combustion of scrap tires in a horizontal, laboratory scale reactor
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A horizontal laboratory reactor was used to study the evolution of byproducts from the combustion of scrap tires at five nominal temperatures (ranging from 650 to 1050 °C) and different oxygen:sample ratios A model was used to calculate the bulk air ratio (λ), and the oxygen consumption was discussed considering this ratio λ. More than 100 volatile and semivolatile compounds were identified and quantified by gas chromatography mass spectrometry, plotting their yields vs the bulk air ratio and temperature. Five different behaviors considering the bulk air ratio and the temperature were identified.
- Fullana,Font,Conesa,Blasco
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p. 2092 - 2099
(2007/10/03)
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- 1,2-shifts of hydrogen atoms in aryl radicals
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An energy barrier on the order of 60 kcal/mol is predicted for the 1,2- shift of hydrogen atoms in aryl radicals. Such rearrangements are, therefore, not expected to occur under ordinary laboratory conditions, but they should be prevalent in the aryl radicals formed during combustion, flash vacuum pyrolysis, and other high-temperature gas-phase processes. As a demonstration of this rearrangement, the 2-benzo[c]phenanthryl radical (1) was generated by flash vacuum pyrolysis of the corresponding aryl bromide (9). A 1,2-shift of hydrogen out of the sterically congested cove region of 1, followed by cyclization and rearomatization of the resulting radical (Scheme 1), is proposed to explain the observation of benzo[ghi]fluoranthene (4) as the dominant monomeric product formed. Under the same conditions, [ 1,3,4,5- 2H4]-2-bromobenzo[c]phenanthrene (13) gives [ 1,2,3,4-2H4]- benzo[ghi]fluoranthene (15) as the dominant monomeric product (Scheme 6), in accord with the expectation of a deuterium atom 1,2-shift.
- Brooks, Michele A.,Scott, Lawrence T.
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p. 5444 - 5449
(2007/10/03)
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- Flash vacuum thermolysis of acenaphtho[1,2-a]acenaphthylene, fluoranthene, benzo[k]- and benzo[j]fluoranthene - Homolytic scission of carbon-carbon single bonds of internally fused cyclopenta moieties at T ≥ 1100°C
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Flash vacuum thermolysis (FVT, 1000 °C ≥ T ≥ 1200 °C) of acenaphtho[1,2-a]acenaphthylene (3, C22H12) gave the C22H12 cyclopenta-fused polycyclic aromatic hydrocarbon (CP-PAH) acenaphtho[1,2- e]acenaphthylene (4), cyclopenta[cd]perylene (5) and cyclopenta[def]benzo[hi]chrysene (6). Whereas the formation of 4 is explained by a ring contraction/ring expansion rearrangement of 3, the identification of 5 and 6 suggests that 3 also undergoes homolytic scission of a five- membered ring's carbon-carbon single bond furnishing the transient diradical intermediate 7. Ring closure of 7 to form 8 after rotation around the carbon- carbon single bond of the intact five-membered ring followed by hydrogen shifts will give 6. The latter can rearrange subsequently into 5 by ring contraction/ring expansion. The structural assignment of 4 and 5 was supported by independent FVT of 6,12-bis(1-chloroethenyl)chrysene (14) and 3- (1-chloroethenyl)perylene (23), respectively. FVT of 14 (900-1200 °C) gave in a consecutive process 6,12-bis(ethynyl)chrysene (15), 9- ethynylbenz[j]acephenanthrylene (16) and bis(cyclopenta[hi,qr])chrysene (17). Although at T ≥ 900 °C 17 selectively rearranges into 4 by ring contraction/ring expansion, at 1200 °C the latter is converted into 5 presumably via a diradical intermediate obtained by homolytic scission of a single carbon-carbon bond of a five-membered ring. FVT of 23 gave in situ 3- ethynylperylene (25), which at 1000 °C is nearly quantitatively converted into 5. The propensity of internal cyclopenta moieties to undergo homolytic scission of a five-membered ring's carbon-carbon single bond was corroborated by independent FVT of benzo[k]- (11) and benzo[j]fluoranthene (12). Previously unknown thermal pathways to important (CP)-PAH combustion effluents are disclosed at T≥ 1000 °C.
- Sarobe, Martin,Kwint, Huibert C.,Fleer, Theun,Havenith, Remco W.A.,Jenneskens, Leonardas W.,Vlietstra, Edward J.,Van Lenthe, Joop H.,Wesseling, Jolanda
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p. 1191 - 1200
(2007/10/03)
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- Synthesis of anti- and syn-Diol Epoxides of trans-3,4-Dihydroxy-3,4-dihydrobenzo[ghi]fluoranthene: Model Planar Diol Epoxides
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We describe the preparation of anti- and syn-3,4-dihydroxy-5,5a-epoxy-3,4,5,5a-tetrahydrobenzo-[ghi]fluoranthene (2 and 3) as model planar diol epoxides. These compounds were synthesized by a dihydroarene method in 10 steps starting from 4H-cyclopenta[def]phenanthrene. These are the first examples of diol epoxides in which a five-membered ring is fused to the saturated ring bearing an epoxide group, and they are the rigid analogues of the extensively studied benzo[c]phenanthrene diol epoxides (5 and 6). In accord with expectation, 1H NMR data indicated that the diol conformations of 2 and 3 are locked into diequatorial and diaxial conformations, respectively, and thus are suitable for comparative DNA binding studies.
- Chang, Hui-Fang,Cho, Bongsup P.
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p. 9051 - 9056
(2007/10/03)
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- Characterization of the combustion products of polyethylene
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Polyethylene (PE) was burned in a tube-type furnace with an air flow at a temperature of 600~900°C. Combustion products were collected with glass wool, glass fiber filter, and XAD-2 adsorbent. The analysis of the products was performed with GC-FID and GC-MSD. At low temperature, hydrocarbons were the major components, while at higher temperature the products were composed of polycyclic aromatic hydrocarbons. With the high performance of the Hewlett-Packard 6890GC-5973MSD, more compounds were identified in comparison with previous studies.
- Piao, Mingjun,Chu, Shaogang,Zheng, Minghui,Xu, Xiaobai
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p. 1497 - 1512
(2007/10/03)
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- Migration of redundant ethynyl substituents along polycyclic aromatic hydrocarbon peripheries. Consequences for polycyclic aromatic hydrocarbon build up
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The formation of cyclopenta[cd]pyrene (5) and benzo[ghi]fluoranthene (6) upon FVT of 3,9-bisethynylphenanthrene (1) and 8-ethynylfluoranthene (2), respectively, suggests that redundant ethynyl substituents, which cannot give five- and/or six-membered ring formation via ethynyl ethylidene carbene equilibration followed by carbene C-H insertion, can migrate along the PAH periphery at high temperatures.
- Sarobe, Martin,Jenneskens, Leonardus W.,Kleij, Arjan,Petroutsa, Maria
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p. 7255 - 7258
(2007/10/03)
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- Fullerene tectonics. Part 2. Synthesis and pyrolysis of halogenated benzo[c]phenanthrenes
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Halogenated benzo[c]phenanthrenes with a halogen in the hindered fiord region are prepared by the photochemical cyclisation of appropriately substituted stilbenes. Pyrolysis gives the corresponding benzo[ghi]fluoranthrenes in moderate yields. At higher temperatures a competing rearrangement pathway to cyclopenta[cd]pyrene occurs.
- Plater, M. John
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p. 2903 - 2909
(2007/10/03)
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- Thermolysis of benzo[c]phenanthrene-5,6-dicarboxylic anhydride and 6H-benzo[cd]pyren-6-one. Entries to the combustion effluents benzo[ghi]fluoranthene and cyclopenta[cd]pyrene
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Thermolysis of the oxy-PAH benzo[c]phenanthrene 5,6-dicarboxylic anhydride (3) and 6H-benzo[cd]pyren-6-one (4) gave the abundant C18H10 CP-PAH combustion effluents benzo[gh]]fluoranthene (1) and cyclopenta[cd]pyrene (2).
- Sarobe, Martin,Jenneskens, Leonardus W.,Wiersum, Ulfert E.
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p. 4689 - 4692
(2007/10/03)
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- Synthesis and Hydropyrolysis of Bis-trimethylsilyl Substituted 3-(4H-Cyclopentaphenanthrylidene)-1,4-pentadiyne. A New Route to Corannulene
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3-(4H-Cyclopentaphenanthrylidene)-1,5-bis-(trimethylsilyl)-1,4-pentadiyne (3) was synthesized and converted by hydropyrolysis into corannulene (1) besides others in reasonable yields.It represents a new route of the simplest bowl-shaped polycyclic aromatic hydrocarbon starting from an easily accessible precursor.
- Zimmermann, Gerhard,Nuechter, Uta,Hagen, Stefan,Nuechter, Matthias
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p. 4747 - 4750
(2007/10/02)
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- Proposed Fullerene Precursor Corannulene Identified in Flames Both in the Presence and Absence of Fullerene Production
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Corannulene, C20H10, a bowl-shaped polycyclic aromatic hydrocarbon whose curvature and carbon framework are similar to those of fullerenes, has been widely hypothesized to be a fullerene precursor but has never been identified in flames, either in the presence or absence of fullerene production.In research on the mechanism and prevalence of fullerene formation in flames, we have identified corannulene in fullerene-producing flames and also in conventional flames that do not produce fullerenes.The identification was achieved using a combination of analytical methods including high performance liquid chromatography with UV-vis spectrometric detection, and gas chromatography coupled with infrared and mass spectrometric detection.The presence of corannulene in fullerene-forming flames is consistent with the hypothesis that corannulene is a fullerene precursor.The presence of corannulene in fullerene-deficient flames does not necessarily contradict this hypothesis and instead may suggest that at least some stages of fullerene formation chemistry are more generally operative in flames than had previously been known.
- Lafleur, Arthur L.,Howard, Jack B.,Marr, Joseph A.,Yadav, Tapesh
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p. 13539 - 13543
(2007/10/02)
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- On the Synthesis of Benzofluoranthene
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Cyclodehydrogenation of benzophenanthrene (1) by platinium gives benzofluoranthene (2).
- Studt, Peter,Win, Tin
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