- Reaction of Polycyclic Aromatic Hydrocarbons with Ozone. Linear Free-Energy Relationships and Tests of Likely Rate-Determining Steps Using Simple Molecular Orbital Correlations
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Nine unsubstituted, polycyclic aromatic hydrocarbons were allowed to react with ozone at 25 deg C, and relative rate constants were obtained by direct competitive techniques.The rate constants show a large variation with substrate structure, with nearly three powers of ten difference between the least reactive (benzene) and most reactive (anthracene, perylene) compounds studied.Linear free-energy relationships between the rate data and calculated molecular orbital parameters have been obtained.The optimum correlations are found for models based on rate-determining ?-complex or ?-complex formation rather than simultaneous addition of ozone to two carbon atoms.Electrophilic attack by ozone to yield a ?-complex also appears to be the rate-determining step based on the results obtained for changes in selectivity with variation of solvents.
- Pryor, William A.,Gleicher, Gerald J.,Church, Daniel F.
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- UVA light-induced DNA cleavage by isomeric methylbenz[a]anthracenes
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UVA light-induced DNA single strand cleavage by a set of 12 monomethyl substituted benz[a]anthracenes (MBAs) along with their parent compound, benz[a]anthracene (BA), and the potent carcinogen, 7,12-dimethylbenz[a]anthracene (DMBA), was studied. On the basis of the relative DNA single strand photocleavage efficiency of the fourteen compounds, they are divided into three groups: (1) strong DNA cleavers, 4-MBA, 5-MBA, 6-MBA, 8-MBA, 9-MBA, 10-MBA, and BA; (2) medium DNA cleavers, 1-MBA, 2-MBA, 3-MBA, and 11-MBA; and (3) weak DNA cleavers, 7-MBA, 12-MBA, and DMBA. The relative DNA photocleavage efficiency parallels very well with the energy gap between the highest-occupied-molecular-orbital (HOMO) and the lowest-unoccupied-molecular-orbital (LUMO) of each MBA, indicating that the DNA cleavage is related to their excited-state properties. The 7 and 12 positions of BA are two unique sites. Methyl substitution at either 7 or 12 (or both) positions lowers the HOMO-LUMO gap and greatly diminishes the DNA photocleavage efficiency. UVA light-induced photodegradation of selected MBAs reveals that methyl substitution at either 7 or 12 (or both) positions greatly enhances the degradation rate. Photodegradation of 7-MBA, 12-MBA, and DMBA yields products that are much less effective in mediating DNA cleavage. Photodegradation of other MBAs, exemplified by 5-MBA, yields a photooxidation product 5-MBA-7,12-quinone which is relatively stable under light and is a stronger DNA photocleaver than 5-MBA itself. The higher efficiency of DNA photocleavage for MBAs with methyl substitution at positions other than 7 or 12 is due, at least in part, to the formation of 7,12-quinone. Light-induced DNA single strand cleavage efficiency for several MBAs parallels the light-induced toxicity observed by other research groups, suggesting that light-induced DNA cleavage of MBAs are the source for phototoxicity. Since some PAHs such as coal tar are used commercially as creams, therapeutic agents, or ointments, or those roofers and asphalt workers that are subject to contamination with PAHs, the combination of PAHs and light (in the skin) may present a greater health risk to humans.
- Dong, Shiming,Fu, Peter P.,Shirsat, Rujendra N.,Hwang, Huey-Min,Leszczynski, Jerzy,Yu, Hongtao
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- Catalytic c-c cleavage/alkyne-carbonyl metathesis sequence of cyclobutanones
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A ring-opening/alkyne-carbonyl metathesis sequence of alkyne-tethered cyclobutanones catalyzed by AgSbF6 is realized for the first time to furnish multisubstituted naphthyl ketones under mild conditions. A range of substrates decorated with various substituents at different positions were all well accommodated. Preliminary mechanistic studies show that silver salt acted as a Lewis acid to facilitate both C-C cleavage of the cyclobutanone moiety and the subsequent metathesis between C═O and CC bonds.
- Gao, Jiqiang,Liu, Chunhui,Li, Zhongjuan,Liang, Haotian,Ao, Yuhui,Zhao, Jinbo,Wang, Yuchao,Wu, Yuanqi,Liu, Yu
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supporting information
p. 3993 - 3999
(2020/06/08)
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- Efficient oxidation of polycyclic aromatic hydrocarbons with H 2O2 catalyzed by 5,10,15-triarylcorrolatoiron (IV) chloride in ionic liquids
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A simple and efficient oxidative system has been developed for the oxidation of polycyclic aromatic hydrocarbons with H2O2 catalyzed by 5,10,15-triarylcorrolatoiron (IV) chloride in mixed reaction media using imidazolium ionic liquids and organic solvents. The coordination effects of different organic solvents as well as anions of ionic liquids on the oxidation reactions have been examined.
- Kumari, Pratibha,Nagpal, Ritika,Chauhan, Shive M.S.
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- Regiospecific oxidation of polycyclic aromatic phenols to quinones by hypervalent iodine reagents
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The hypervalent iodine reagents o-iodoxybenzoic acid (IBX) and bis(trifluoro-acetoxy)iodobenzene (BTI) are shown to be general reagents for regio-controlled oxidation of polycyclic aromatic phenols (PAPs) to specific isomers (ortho, para, or remote) of polycyclic aromatic quinones (PAQs). The oxidations of a series of PAPs with IBX take place under mild conditions to furnish the corresponding ortho-PAQs. In contrast, oxidations of the same series of PAPs with BTI exhibit variable regiospecificity, affording para-PAQs where structurally feasible and ortho-PAQs or remote PAQ isomers in other cases. The structures of the specific PAQ isomers formed are predictable on the basis of the inherent regioselectivities of the hypervalent iodine reagents in combination with the structural requirements of the phenol precursors. IBX and BTI are recommended as the preferred reagents for regio-controlled oxidation of PAPs to PAQs.
- Wu, Anhui,Duan, Yazhen,Xu, Daiwang,Penning, Trevor M.,Harvey, Ronald G.
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experimental part
p. 2111 - 2118
(2010/04/26)
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- Photocatalytic degradation of polycyclic aromatic hydrocarbons in GaN:ZnO solid solution-assisted process: Direct hole oxidation mechanism
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GaN:ZnO exhibits excellent activity for the photodegradation of PAHs, and the activity can be obviously improved by loading Pt. The degradation of PAHs in the system of GaN:ZnO is induced by the formation of holes. The holes generated then interact with PAHs to produce PAHs+, which is active enough to react with O2.
- Kou, Jiahui,Li, Zhaosheng,Guo, Yong,Gao, Jun,Yang, Ming,Zou, Zhigang
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experimental part
p. 48 - 54
(2010/10/01)
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- The synthesis of angularly fused polyaromatic compounds by using a light-assisted, base-mediated cyclization reaction
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The synthesis of substituted polyaromatic compounds that contain at least four benzene rings fused together in an angular fashion is described. Suzuki coupling of 1-bromo-3,4-dihydronaphthalene-2-carbaldehyde with a number of aromatic boronic acids affords products such as 1-(1,4-dimethoxy-3-methyl-2-naphthyl)-3,4-dihydronaphthalene-2-carbaldehyde. Exposure of these dihydronaphthalenes to potassium tert-butoxide and DMF at 80°C yields polyaromatic compounds such as 9,14-dimethoxynaphtho[1,2-a]anthracene.
- Pathak, Rakhi,Vandayar, Kantharuby,Van Otterlo, Willem A. L.,Michael, Joseph P.,Fernandes, Manuel A.,De Koning, Charles B.
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p. 3504 - 3509
(2007/10/03)
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- Acid-Catalyzed Cyclization of o-Aroylbenzoic and Diarylcarboxylic Acids upon Heating in Vacuum
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The cyclization of 1,1′-dinaphthyl-8,8′-dicarboxylic acid, diphenic anhydride, o-benzoylbenzoic acid, and 1-naphthoyl-o-benzoic acid into, respectively, anthanthrone, fluorenone-4-carboxylic acid, anthraquinone, and 1,2-benzanthraquinone occurs upon heating to 150-200°C in vacuum in the presence of catalytic amounts (1-3%) of H2SO4 or P2O5.
- Nefedov
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p. 375 - 377
(2007/10/03)
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- The Nucleophilicity of Superoxide towards Different Alkyl Halides Estimated from Kinetic Measurements
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Values of the rate constant ksub are measured for the substitution reaction between superoxide O2 anion-radical and the alkyl halides butyl chloride, 2-butyl chloride, benzyl chloride, ethyl bromide, butyl bromide, 2-butyl bromide, neopentyl bromide, benzyl bromide, (1-bromo-2,2-dimethylpropyl)benzene and 1-iodoadamantane.These rate constants are compared with the expected rate constant kET for the electron transfer reaction between the same alkyl halides and an aromatic anion radical A anion-radical with the same standard oxidation potential as O2 anion-radical.The ksub/kET ratios show that the mechanism of the substitution reaction amy shift from SN2-like to ET-like on changes in the steric hindrance and the acceptor ability of the alkyl halide.The influence on ksub/kET of the difference in self-exchange reorganization energy λ(0) between O2 anion-radical/O2 and A anion-radical/A is discussed.
- Daasbjerg, Kim,Lund, Henning
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p. 597 - 604
(2007/10/02)
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- Oxidation of Polynuclear Aromatic Hydrocarbons with Ceric Ammonium Sulfate: Preparation of Quinones and Lactones
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The oxidation of polynuclear aromatic hydrocarbons with ceric ammonium sulfate (CAS) in sulfuric acid was investigated.Oxidation of benzofluoranthene (1) gave a mixture of the 7,12- and 2,3-diones 3 and 4.The 2,3-dione (4) was used as the starting material for a facile synthesis of 2,3-dihydro-2,3-dihydroxybenzofluoranthene (5) and the corresponding diol epoxide 6, which are potentially important metabolites of benzofluoranthene.In a similar manner, 2,3-dihydro-2,3-dihydroxyfluoranthene (7) and its diol epoxide 8 were prepared from fluoranthene.Oxidation of benzofluoranthene (2) with CAS did not yield quinones, but instead gave benzofluorenopyran-5,13-dione (9), which was identified by its spectral properties and by reduction with LiAlH4.The lactone 9 formed via initial K-region oxidation of 2.It was not formed from 1-hydroxybenzofluoranthene (12), which gave benzofluoranthene-1,2-dione (13) upon CAS oxidation.CAS oxidation of benzopyrene (14) gave a mixture of the 1,6- and 3,6-quinones 17 and 18.Treatment of benzanthracene (15) with CAS yielded 7-oxo-12-hydroxy-7,12-dihydrobenzanthracene (19) and the 7,12-quinone 20.Oxidation of chrysene (16) with CAS gave 6H-benzonaphthopyran-6-one (21) and the 5,6-quinone 22.The results of this study demonstrate that CAS oxidation is useful for the synthesis of certain PAH quinones or lactones, from polynuclear aromatic hydrocarbons, depending on the ring system.
- Balanikas, George,Hussain, Nalband,Amin, Shantu,Hecht, Stephen S.
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p. 1007 - 1010
(2007/10/02)
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- Improved Synthesis and Crystal Structure of 7H-Dibenzanthracen-7-one
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An improved synthetic method gives pure 7H-dibenzanthracen-7-one, C21H12O, in a higher yield than those reported so far.The crystal structure has been determined by X-ray analysis.The space group is Pn21a, with unit cell dimensions of a=23.325(5), b=14.149(3), c=3.986(1) A, and Z=4.The structure was solved by the direct method and refined by the block-diagonal least-squares method to an R value of 0.044.The molecule is greatly distorted from the planar conformation because of an intramolecular steric repulsion between the hydrogen atoms.
- Fujisawa, Shoi,Oonishi, Isao,Aoki, Junji,Ohashi, Yuji,Sasada, Yoshio
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p. 3356 - 3359
(2007/10/02)
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- Synthetic Routes to Benzanthracenes via Transient 1-Benzylisobenzofuran Derivatives
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A synthetic route to 7-acetoxybenzanthracenes is described based on the generation of 1-benzylisobenzofurans and their capture with methyl acrylate in a Diels-Alder reaction.The 1,4-epoxy-1,2,3,4-tetrahydronaphthalene derivatives so formed are aromatized to naphthoate esters under acidic conditions and hydrolyzed to the naphthoic acids, and these are cyclized to the 7-acetoxybenzanthracenes with zinc chloride in acetic anhydride.
- Smith, James G.,Welankiwar, Sudha S.,Chu, Noreen G.,Lai, Eric H.,Sondheimer, Susan J.
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p. 4658 - 4662
(2007/10/02)
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- A New Route to Anthraquinones
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The lithium salts derived from position 3 of phthalides react with arynes to form adducts, which, upon aerial oxidation, produce anthraquinones in moderate to good yields.Substituted phthalides and arynes also participate in this general reaction.The addition to unsymmetrically substituted arynes shows regioselectivity, whilst the availability of a new general route to phthalides extends the scope of this reaction.
- Dodsworth, David J.,Calcagno, Maria-Pia,Ehrmann, E. Ursula,Devadas, Bhatt,Sammes, Peter G.
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p. 2120 - 2124
(2007/10/02)
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