- Electronic spectra of radical cations and their correlation with photoelectron spectra-III. Perylenes and coronenes
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Radical cations of perylene, 1,12-benzoperylene, coronene, 1,2-benzocoronene, and naphtho-(2',3':1,2)coronene are produced by photooxidation in boric acid matrix and their electronic absorption spectra are measured.The results are discussed in terms of Longuet-Higgins-Pople and Wasilewski type Open-Shell SCF-MO calculations and the u.v. photoelectron spectra of the parent molecules.The correspondence between optical and photoelectron spectra is found to be fairly good.A correlation diagram for the electronic transitions for some of the molecular ions is presented to demonstrate their movement from one system to another.Finally, an express ion showing the relationship between the first ionization potentials of the parent molecules and A-type electronic band energies in the cation spectra is given from which the first IP's of the hydocarbons may be estimated.
- Khan, Zahid H.
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- Electron Transfer from CO2.- to Perylene in Cyclohexane
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CO2.- formed by the reaction of the electron with CO2 in cyclohexane transfers an electron to perylene with a rate constant of 2.9 * 1010 M-1 s-1.Gε580nm for the perylene radical anion is 9 * 103 molecules (100 eV)-1 M-1 cm-1.The transfer of an electron from CO2.- to an aromatic molecule is a significant process when CO2 is used as an electron scavenger in solutions where the production of excited states of the aromatic molecule is studied.
- Sauer, Myran C.,Jonah, Charles D.
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- Temperature Coefficients of Half-wave Potentials and Entropies of Transfer of Cations in Aprotic Solvents
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Temperature coefficients of polarographic half-wave potentials for Li+, Na+, K+, Rb+, Cs+, Tl+, Cu2+, Zn2+, Cd2+, Ba2+, Pb2+, bis(biphenyl)chromium(I) tetraphenylborate, ferrocene and perylene have been derived from measurements vs.Ag/Ag+ (0.01 mol dm-3) electrodes kept at 25 deg C in 0.1 mol dm-3 solutions of tetrabutylammonium perchlorate in dimethyl sulphoxide, N,N-dimethylformamide, hexamethylphosphoric triamide and propylene carbonate.Entropies for the above mentioned redox couples and for Ag+ were calculated for reversible electrode reactions on the basis of the assumption of a negligible thermal diffusion potential.This assumption was also employed to calculate single-ion entropies of transfer from N,N-dimethylformamide into dimethyl sulphoxide, propylene carbonate and hexamethylphosphoric triamide.
- Gritzner, Gerhard,Lewandowski, Andrzej
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- Transient absorption spectroscopy of high-mobility ions in decalin
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Transient absorption spectroscopy is used to demonstrate that pulse radiolysis of a decalin mixture (63% cis-decalin + 37% trans-decalin) with 15 MeV electrons results in formation of high-mobility solvent holes. These radical cations react with perylene with a rate constant of 8.5 × 1010 mol-1 dm3 s-1. This scavenging is faster by an order of magnitude than ion-molecule reactions of normally diffusing ions (～(5-7.5) × 109 mol-1 dm3 s-1). Under conditions of the experiment, the lifetime of the rapidly migrating solvent holes is ～150 ns, which identifies them as the high-mobility cations observed by dc and microwave conductivity.
- Shkrob,Sauer Jr.,Yan,Trifunac
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- Photoinduced Electron-Transfer Reactions of Perylene in Acetonitrile
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Laser-flash-photolysis experiments show that, in MeCN at 20 deg, perylene (P) undergoes three distinct electron-transfer reactions: a) 1P* + MeCN -> P.+ + MeCN.- b) 1P* + P -> P.+ + P.- c) 3P* + 3P* -> (P x P)* -> P.+ + P.-.These processes originate probably from the thermally relaxed excited states of P.
- Vauthey, Eric,Suppan, Paul,Haselbach, Edwin,Davidson, Robert Stephen
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- peri-Naphthylenediamines 24.* Double 1,1′-binaphthalene "proton sponge"
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4,5,4′,5′-Tetrakis(dimethylamino)-1,1′-binaphthalene, unknown previously, was obtained in -20% yield by the oxidation of 1,8-bis(dimethylamino)naphthalene with Tl(OAc)3 or Pb(OAc)4 at low temperatures. Treatment of the reaction produ
- Vistorobskii,Pozharskii,Rudnev
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- Mechanism of the Formation of Transient Aromatic Radical Cations in Alcohols: Laser Flash Photolysis and Pulse Radiolysis Studies
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A product of the reaction of SF6 with a solvated electron in an alcohol (presumably SF5.) reacts with an aromatic solute molecule such as anthracene, perylene, naphthalene, or hexamethylbenzene to form aromatic radical cations.This reaction depends on both the ionization potential of the aromatic solute molecule and the polarity of the solvent.The rates of these reactions are (except for naphthalene) in the range of (1-10) * 109 M-1 s-1.The reaction of the aromatic molecule (except for naphthalene) with SF5. appears to have two pathways, one of which leads to the radical cation and a second that forms an undetermined product.
- Liu, A.-D.,Sauer, M. C.,Jonah, C. D.,Trifunac, A. D.
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- Flash vacuum thermolysis of acenaphtho[1,2-a]acenaphthylene. Thermal behaviour of a polycyclic aromatic hydrocarbon containing two abutting pentagons
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FVT of acenaphtho[1,2-a]acenaphthylene (1) gave acenaphtho[1,2- elacenaphthylene (2). cyclopenta[cd]perylene (3) and cyclopenia[rst]benzo[hi]chrysene (4). The formation of 3 and 4 indicates that, besides ring contraction/ring expansion of 1 giving 2, homolytic scission of a five-membered ring carbon-carbon single bond of 1 is an important competitive process.
- Sarobe, Martin,Kwint, Huibert C.,Fleer, Theun,Jenneskens, Leonardus W.,Wesseling, Jolanda
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- Colloid chemical reaction route to the preparation of nearly monodispersed perylene nanoparticles: Size-tunable synthesis and three-dimensional self-organization
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By employing a colloid chemical reaction method we demonstrate the preparation of organic nanoparticles composed of perylene molecules (PeNPs) based on the reduction of perylene perchlorate by Br- anions in the presence of cetyl trimethyl ammonium bromide (CTA+Br-) in acetonitrile. A discrete nucleation event, followed by a slower controlled growth on the existing particles, is identified during formation of PeNPs. By changing the growth parameters, such as the monomer concentration and the method of injection, quasi-spherical PeNPs with controllable sizes from 25 to 90 nm could be obtained. The homogeneous solution phase of this method makes it capable of large-scale synthesis of PeNPs with a size distribution (+ around the PeNPs. The three-dimensional, hierarchical self-organization of 25-nm PeNPs building blocks is observed to form nanobelts and square nanorods, possibly templated by the CTA+ lamellar micelle structures in acetonitrile. Spectroscopic results reveal two kinds of trends in the development of the optical properties of perylene as they evolve from the molecular to the bulk phase in the nanometer range. The so-called size dependence is evidenced by a switch from Y-type to E-type excimers as the size of the PeNPs increased from 25 to 90 nm. As the 25-nm PeNPs organize into nanobelts or square nanorods the oscillator strength of the Y-type excimers is relatively enhanced. That is, collective phenomena develop as the proximal particles interact in the glassy solids. Our very recent results indicate that this colloid chemical reaction method can also be applied to other organic compounds.
- Kang, Longtian,Wang, Zhechen,Cao, Zongwei,Ma, Ying,Fu, Hongbing,Yao, Jiannian
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- Light-Induced Charge Separation by Formation of Insoluble Precipitates
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Preliminary experiments are reported on light-induced charge separation by quenching electronically excited species with formation of insoluble precipitates.Irradiation of acceptor-donor mixtures of 3-dimethylaminoperylene metaphosphate/tetramethyl-p-phenylenediamine (TMPD) and of Ag+/perylene, respectively, in methylene chloride and with tetrabutylammonium perchlorate as supporing electrolyte formed precipitates of TMPD+ClO4- and Ag, respectively.The precipitates were separated from the solution by a platinum filter in a flow cell, which served as a simple battery for conversion of stored chemical energy into electrical energy.The quantum yield was about 1E-6 and the battery voltage about 60 mV.
- Grabner, Erich Walter,Hessberger, Harald
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- Evidence for Single Electron Transfer in the Reactions of Alkali Metal Amides and Alkoxides with Alkyl Halides and Polynuclear Hydrocarbons
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Evidence for single electron transfer as the major pathway in reactions previously considered to be classic SN1 and SN2 pathways has been obtained.In this connection, the reaction of KOBu-t with trityl bromide has been shown to proceed through the trityl radical, and the reaction of LiN(i-Pr)2 with a primary alkyl iodide probe gave evidence of proceeding by single electron transfer, as indicated by the cyclized nature of the product as a result of a radical intermediate.
- Ashby, E. C.,Goel, A. B.,DePriest, R. N.
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- An oxidation induced by potassium metal. Studies on the anionic cyclodehydrogenation of 1,1′-binaphthyl to perylene
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Oxidative cyclization of 1,1′-binaphthyl (1) to perylene (2) can be achieved in essentially quantitative yield by the action of three or more equivalents of potassium metal in hot tetrahydrofuran. An overall reaction mechanism is proposed that accounts for all of the experimental observations reported by previous investigators and those from the present studies. The trans-6a,6b-dihydroperylene dianion (62-) is believed to be the pivotal intermediate from which H2 is lost. A radical chain reaction involving free hydrogen atoms (H?) in the two-step propagation cycle is proposed to explain the formation of H2 from 62-. Anionic cyclodehydrogenations of this sort are complementary to those performed under strongly acidic/oxidizing conditions, photochemically, or thermally (flash vacuum pyrolysis), and a better understanding of how they occur, together with the optimized synthetic protocol reported here, should encourage their wider use in organic synthesis.
- Rickhaus, Michel,Belanger, Anthony P.,Wegner, Hermann A.,Scott, Lawrence T.
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- Arenium cation or radical cation? An insight into the cyclodehydrogenation reaction of 2-substituted binaphthyls mediated by Lewis acids
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Perylene and its derivatives are some of the most interesting chromophores in the field of molecular design. One of the most employed methodologies for their synthesis is the cyclodehydrogenation of binaphthyls mediated by Lewis acids. In this article, we investigated the cyclodehydrogenation reaction of 2-substituted binaphthyls to afford thebay-substituted perylene. By using AlCl3as a Lewis acid and high temperatures (the Scholl reaction), two new products bearing NH2and N(CH3)2groups at position 2 of the perylene ring were synthesized. Under these conditions, we were also able to obtain terrylene from ternaphthalene in 38percent yield after two cyclodehydrogenation reactions in a single step. The attempts to promote the formation of a radical cation (necessary intermediary for the oxidative aromatic coupling mechanism) by using FeCl3or a strong oxidant like 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) did not yield the expected products. DFT calculations suggested that the lack of reaction for oxidative aromatic coupling is caused by the difference between the oxidation potentials of the donor/acceptor couple. In the case of the Scholl reaction, the regiochemistry involved in the formation of the σ-complex together with the activation energy of the C-C coupling reaction helped to explain the differences in the reactivity of the different substrates studied.
- Baumgartner, María T.,Camargo Solórzano, Patricia,Jimenez, Liliana B.,Puiatti, Marcelo
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p. 21974 - 21985
(2020/07/03)
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- A Dynamic Tetracationic Macrocycle Exhibiting Photoswitchable Molecular Encapsulation
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Designing macrocycles with appropriate molecular recognition features that allow for the integration of suitable external stimuli to control host-guest processes is a challenging endeavor which enables molecular containers to solubilize, stabilize, and separate chemical entities in an externally controllable manner. Herein, we introduce photo- and thermal-responsive elements into a semi-rigid tetracationic cyclophane, OPVEx2Box4+, that is composed of oligo(p-phenylenevinylene) pyridinium units and the biphenylene-bridged 4,4-bipyridinium extended viologens and adopts a rectangle-like geometry. It transpires that when the photoactive oligo(p-phenylenevinylene) pyridinium unit is incorporated in a macrocyclic scaffold, its reversibility is dramatically improved, and the configurations of the cyclophane can go back and forth between (EE)- and (EZ)-isomers upon alternating blue light irradiation and heating. When the macrocycle is found in its (EE)-configuration, it is capable of binding various π-electron-rich guests - e.g., anthracene and perylene - as well as π-electron-deficient guests - e.g., 9,10-anthraquinone and 5,12-tetracenequinone - through charge-transfer and van der Waals interactions. When irradiated with blue light, the (EE)-isomer of the cyclophane can be transformed successfully to the (EZ)-isomer, resulting in the switching off of the binding affinity for guest molecules, which are bound once again upon heating. The use of light and heat as external stimuli to control host-guest interactions involving a multi-responsive host and various guests provides us with a new opportunity to design and construct more-advanced molecular switches and machines.
- Wu, Huang,Chen, Yong,Zhang, Long,Anamimoghadam, Ommid,Shen, Dengke,Liu, Zhichang,Cai, Kang,Pezzato, Cristian,Stern, Charlotte L.,Liu, Yu,Stoddart, J. Fraser
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supporting information
p. 1280 - 1289
(2019/01/14)
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- Scholl Cyclizations of Aryl Naphthalenes: Rearrangement Precedes Cyclization
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In 1910, Scholl, Seer, and Weitzenbock reported the AlCl3-catalyzed cyclization of 1,1′-binaphthyl to perylene. We provide evidence that this classic organic name reaction proceeds through sequential and reversible formation of 1,2′- and 2,2′-binaphthyl isomers. Acid-catalyzed isomerization of 1,1′-binaphthyl to 2,2′-binaphthyl has been noted previously. The superacid trifluoromethanesulfonic acid (TfOH), 1 M in dichloroethane, catalyzes these rearrangements, with slower cyclization to perylene. Minor cyclization products are benzo[k]fluoranthene and benzo[j]fluoranthene. At ambient temperature, the observed equilibrium ratio of 1,1′-binaphthyl, 1,2′-binaphthyl, and 2,2′-binaphthyl is 1:3:97. DFT calculations with the inclusion of solvation support a mechanistic scheme in which ipso-arenium ions are responsible for rearrangements; however, we cannot distinguish between arenium ion and radical cation mechanisms for the cyclization steps. Under similar reaction conditions, 1-phenylnaphthalene interconverts with 2-phenylnaphthalene, with the latter favored at equilibrium (5:95 ratio), and also converts slowly to fluoranthene. Computations again support an arenium ion mechanism for rearrangements.
- Skraba-Joiner, Sarah L.,McLaughlin, Erin C.,Ajaz, Aida,Thamatam, Rajesh,Johnson, Richard P.
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p. 9578 - 9583
(2015/10/12)
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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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- SEPARATION OF NANOPARTICLES
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This invention is directed to separation, optimization and purification of nano-materials using self-assembled perylene diimide membranes, wherein said perylene diimide membrane is recyclable.
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(2013/11/19)
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- FLUORINE-SUBSTITUTED PERYLENES FOR COLOUR FILTERS IN LCDS
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Use of fluorine-substituted perylenes in colour filters for liquid-crystal displays.
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- Polyether polyol dendron conjugates with effector molecules for biological targeting
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Subject of the present invention are polyether polyol dendron conjugates comprising a specific polyether polyol dendron moiety, at least one certain fluorescent effector molecule (E). Such polyether polyol dendron conjugates may be used for diagnostic and therapeutic purposes, whereby the optical properties of the at least one certain fluorescent effector molecule are enhanced due to the attachment to the polyether polyol dendron conjugate.
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- Microwave flash pyrolysis
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(Chemical Equation Presented) In a microwave reactor, graphite heats rapidly to high surface temperatures; applications of graphite thermal "sensitization" have been described previously. We report here that microwave thermal sensitization with graphite, carbon nanotubes, or silicon carbide can be used to carry out reactions more typically accomplished by flash vacuum pyrolysis (FVP) and which usually require temperatures much higher than the nominal limit of a microwave reactor. The graphite-sensitized microwave reaction of azulene in the solid phase at temperatures of 100 to 300°C affords rapid rearrangement to naphthalene, a reaction typically observed by FVP at 700-900°C. Multiwall carbon nanotubes give similar results when used as a thermal sensitizer. Other graphite-sensitized reactions that we have observed include the following: conversion of 2-ethynylbiphenyl to phenanthrene, fragmentation of phthalic anhydride to benzyne, cleavage of iodobenzene to phenyl radical, aryl-aryl bond cleavage, and a variety of cycloaromatizations. An advantage is seen for less volatile substrates. Rearrangement of azulene and generation of benzyne from phthalic anhydride have also been observed on powdered silicon carbide. Because of the high temperature, rapid heating, and frequent ejection of material from the irradiation zone, we refer to this general method as microwave flash pyrolysis (MFP).
- Hee, Yeon Cho,Ajaz, Aida,Himali, Dibya,Waske, Prashant A.,Johnson, Richard P.
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supporting information; experimental part
p. 4137 - 4142
(2009/09/25)
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- Organic Silane Compound, Method of Producing the Same, and Organic Thin Film Using the Same
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The present invention provides a highly ordered, crystallized organic thin film superior in electroconductive properties that is resistant to exfoliation, a compound for preparation of the thin film, and a method of producing the same. An organic silane compound, characterized in that a molecule represented by General Formula (I) is substituted with a silyl group. A method of producing the organic silane compound, comprising halogenating a molecule (I) and allowing it to react with a silane derivative. An organic thin film, wherein the organic silane compound molecule is oriented with its silyl group located in the substrate side and the molecule (I) region in the film surface side. (wherein, x1 and x2 are integers satisfying 1≦x1, 1≦x2, and 2≦x1+x2≦8; each of y1 and z1 is independently an integer of 2 to 8; each of y2 and z2 is independently an integer of 0 to 8; and the skeleton may be substituted with a hydrophobic group).
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Page/Page column 5-6
(2009/01/24)
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- Iron (III) perchlorate adsorbed on silica gel: A reagent for organic functional group transformations
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Adsorption of Fe(ClO4)3(H2O)6 onto chromatographic-grade silica gel in the presence of organic solvents (S=water, acetonitrile, or lower fatty acids) produces a supported reagent, Fe(ClO4)3(S)6/SiO2. This reagent has been found to be effective for the rapid organic functional group transformations such as dimerization of alkynes, aromatic hydrocarbons, selective oxidation of thiols to disulfides, and transannular reactions in 1,5-cyclooctadienes on grinding using pestle and mortar in the solid state. Copyright Taylor & Francis Group, LLC.
- Parmar, Anupama,Kumar, Harish
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p. 2301 - 2308
(2008/02/10)
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- Fluorinated dyes or colorants and their uses
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This invention relates to novel fluorinated dyes or colorants having high solubility and low viscosity in halogenated, especially fluorinated, solvents. The dyes or colorants of the present invention have shown to improve the performance of electrophoretic displays.
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- Autocatalytic alkyne cycloadditions: Evidence for colloidal Pt catalysis
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Treatment of the four-membered platinacycle L2Pt(1,8-naphthalendiyl) (1) or the five-membered platinacycle L2Pt(1,12-triphenylendiyl) with excess PhCCPh at 120-150 °C gives the coupling products 1,2-diphenylacenaphthalene or 4,5-diphenylbenzo[e]pyrene and the alkyne complex L2Pt(η2-PhCCPh). Both reactions show an accelerating rate, which has been traced to catalysis of the reaction by colloidal platinum formed by the reaction of O2 with L2Pt(η2-PhCCPh). Copyright
- Begum, Rowshan Ara,Chanda, Nripen,Ramakrishna,Sharp, Paul R.
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p. 13494 - 13495
(2007/10/03)
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- Semivolatile and volatile compounds in combustion of polyethylene
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The evolution of semivolatile and volatile compounds in the combustion of polyethylene (PE) was studied at different operating conditions in a horizontal quartz reactor. Four combustion runs at 500 and 850°C with two different sample mass/air flow ratios and two pyrolytic runs at the same temperatures were carried out. Thermal behavior of different compounds was analyzed and the data obtained were compared with those of literature. It was observed that α,ω-olefins, α-olefins and n-paraffins were formed from the pyrolytic decomposition at low temperatures. On the other hand, oxygenated compounds such as aldehydes were also formed in the presence of oxygen. High yields were obtained of carbon oxides and light hydrocarbons, too. At high temperatures, the formation of polycyclic aromatic hydrocarbons (PAHs) took place. These compounds are harmful and their presence in the combustion processes is related with the evolution of pyrolytic puffs inside the combustion chamber with a poor mixture of semivolatile compounds evolved with oxygen. Altogether, the yields of more than 200 compounds were determined. The collection of the semivolatile compounds was carried out with XAD-2 adsorbent and were analyzed by GC-MS, whereas volatile compounds and gases were collected in a Tedlar bag and analyzed by GC with thermal conductivity and flame ionization detectors.
- Font, Rafael,Aracil, Ignacio,Fullana, Andrés,Conesa, Juan A.
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p. 615 - 627
(2007/10/03)
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- Perylene mixtures
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A process for the preparation of perylene mixtures comprised of at least two symmetrical perylene bisamide dimers of Formula 1 wherein R is hydrogen, alkyl, cycloalkyl, substituted alkyl, aryl, substituted aryl, aralkyl or substituted aralkyl, and at least one terminally unsymmetrical dimer of Formula 2 wherein R1and R2are hydrogen, alkyl, cycloalkyl, substituted alkyl, aryl, substituted aryl, aralkyl, or substituted aralkyl, and wherein R1and R2are dissimilar, which process comprises the condensation of a mixture of at least two perylene monoimide-monoanhydrides of Formula 3 with a diamine wherein R is hydrogen, alkyl, cycloalkyl, substituted alkyl, aryl, substituted aryl, aralkyl, and substituted aralkyl, with a 1,3-diaminopropane.
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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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- Evaluation of acute toxicity and genotoxicity of liquid products from pyrolysis of Eucalyptus grandis wood
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Slow pyrolysis of Eucalyptus grandis wood was performed in an oven laboratory, and smoke was trapped and condensed to yield liquid products. Polycyclic aromatic hydrocarbons (PAHs) and phenolic fractions were isolated from the former liquid products using adsorption column chromatography (ACC) and identified by GC/MS. Concentrations of PAH and phenolic fractions in total pyrolysis liquids were respectively 48.9 μg/g and 8.59% (w/w). Acute toxicity of total samples of pyrolysis liquids and the phenolic fraction was evaluated by means of two bioassays, namely, 24-h immobilization bioassay with Daphnia magna and Microtox(TM) bioassays, the latter employing the luminescent bacteria Photobacterium phosphoreum. Total pyrolysis liquids and the PAH fraction were evaluated for genotoxicity by the Microtox(TM) bioassay conducted using rehydrated freeze-dried dark mutant of the luminescent bacteria Vibrio fisheri strain M169. Total pyrolysis liquids and the phenolic fraction, respectively, in concentrations of 170 and 68 mg/L were able to immobilize 50% (EC50) of the D. magna population following 24-h exposure. Concentrations of 19 and 6 mg/L, respectively, for total pyrolysis liquids and phenolic fraction were the effective concentrations that resulted in a 50% (EC50) reduction in light produced by bacteria in the Microtox(TM) bioassay. Accordingly, the Microtox(TM) bioassay was more sensitive to toxic effects of both kind of samples than the D. magna bioassay, particularly for the phenolic fraction. Regarding to the genotoxicity evaluation, the results achieved by Microtox(TM) bioassay showed that total pyrolysis liquids had no genotoxic effects with and without exogenous metabolic activation using rat liver homogenate (S9). However, the PAH fraction showed toxic effects with rat liver activation and had a dose-response number (DRN) equal to 1.6, being in this way suspected genotoxic. The lowest detected concentration (LDC) of the PAH fraction able to cause genotoxic effects was 375 μg/L.
- Pimenta,Bayona,Garcia,Solanas
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p. 169 - 175
(2007/10/03)
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- Combustion of high calorific value waste material: Organic atmospheric pollution
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Waste tire combustion in an atmospheric fluidized-bed (AFB) reactor (7 cm i.d., 76 cm height) has been performed in a laboratory plant with the aim of studying the polycyclic aromatic hydrocarbon (PAH) emissions as a function of combustion temperature. The main aim has been to compare these organic emissions with the ones obtained when coal is burned at the same combustion conditions. PAH emissions have been analyzed in solids collected in two cyclons at the exit of the reactor and in a trap system formed by a condenser, a filter (20 μm), and an adsorbent. After PAH extraction with dimethylformamide (DMF) by sonication, fluorescence spectroscopy in the synchronous mode (FS) has been used as an analytical technique to quantify the PAHs emitted. It could be concluded that higher PAH emissions are generated when this waste material is burnt at the same conditions used for coal atmospheric fluidized-bed combustion (AFBC).
- Mastral, Ana M.,Callen, Maria S.,Murillo, Ramon,Garcia, Tomas
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p. 4155 - 4158
(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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- Kinetics of the reduction of dialkyl peroxides. New insights into the dynamics of dissociative electron transfer
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The concerted dissociative reduction of di-tert-butyl peroxide (DTBP), dicumyl peroxide (DCP), and di-n-butyl peroxide (DNBP) is evaluated by both heterogeneous and homogeneous electron transfer using electrochemical methods. Electrochemical and thermochemical determination of the O-O bond energies and the standard potentials of the alkoxyl radicals allow the standard potentials for dissociative reduction of the three peroxides in N,N-dimethylformamide and acetonitrile to be evaluated. These values allowed the kinetics of homogeneous ET reduction of DTBP and DCP by a variety of radical anion donors to be evaluated as a function of overall driving force. Comparison of the heterogeneous ET kinetics of DTBP and DNBP as a function of driving force for ET allowed the distance dependence on the reduction kinetics of the former to be estimated. Results indicate that the kinetics of ET to DTBP is some 0.8 order of magnitude slower in reactivity than DNBP because of a steric effect imposed by the bulky tert-butyl groups. Experimental activation parameters were measured for the homogeneous reduction of DTBP with five mediators, covering a range of 0.4 eV in driving force over the temperature range -30 to 50°C in DMF. The temperature dependence of the kinetics leads to unusually low preexponential factors for this series. The low preexponential factor is interpreted in terms of a nonadiabatic effect resulting from weak electronic coupling between the reactant and product surfaces. Finally, the data are discussed in the context of recent advances of dissociative electron transfer reported by Saveant and by German and Kuznestov. In total the results suggest that these peroxides undergo a nonadiabatic dissociative electron transfer and represent the first reported class of compounds where this effect is reported.
- Donkers, Robert L.,Maran, Flavio,Wayner, Danial D. M.,Workentin, Mark S.
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p. 7239 - 7248
(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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- Characterization of polycyclic aromatic hydrocarbon particulate and gaseous emissions from polystyrene combustion
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The partitioning of polycyclic aromatic hydrocarbons (PAHs) between the particulate and gaseous phases resulting from the combustion of polystyrene was studied. A vertical tubular flow furnace was used to incinerate polystyrene spheres (100-300 μm) at different combustion temperatures (800- 1200 °C) to determine the effect of temperature and polystyrene feed size on the particulate and gaseous emissions and their chemical composition. The furnace reactor exhaust was sampled using real-time instruments (differential mobility particle sizer and/or optical particle counter) to determine the particle size distribution. For chemical composition analyses, the particles were either collected on Teflon filters or split into eight size fractions using a cascade impactor with filter media substrates, while the gaseous products were collected on XAD-2 adsorbent. Gas chromatography/mass spectroscopy (GC/MS) was used to identify and quantify the specific PAH species, their partitioning between the gas and particulate phases, and their distribution as a function of emission particle size. The total mass and number of PAH species in both the particulate and gas phases were found to decrease with increasing incineration temperature and decreasing polystyrene feed size, while the mean diameter of the particles increases with increasing incineration temperature and decreasing feed size. In addition, the PAH species in the particulate phase were found to be concentrated in the smaller aerosol sizes. The experimental results have been analyzed to elucidate the formation mechanisms of PAHs and particles during polystyrene combustion. The implications of these results are also discussed with respect to the control of PAH emissions from municipal waste-to-energy incineration systems. The partitioning of polycyclic aromatic hydrocarbons (PAHs) between particulate and gaseous phases resulting from the combustion of polystyrene was studied. A vertical tubular flow furnace was used to incinerate polystyrene spheres to determine the effect of temperature and polystyrene feed size on the particulate and gaseous emissions and their chemical composition. The furnace reactor exhaust was sampled using real-time instruments to determine the particle size distribution. The total mass and number of PAH species in both the particulate and gas phases were found to decrease with increasing incineration temperature and decreasing polystyrene feed size, while the mean diameter of the particles increases with increasing incineration temperature and decreasing feed size. In addition, the PAH species in the particulate phase were found to be concentrated in the smaller aerosol sizes.
- Durlak, Susan K.,Biswas, Pratim,Shi, Jichun,Bernhard, Mary Jo
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p. 2301 - 2307
(2007/10/03)
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- The impact of turbulent mixing on the oxidation of a chlorinated hydrocarbon
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Combustion of chlorinated wastes can lead to the formation of hazardous byproducts. Rates of mixing of fuel and air in combustion systems can have an impact on the composition of the byproducts. Methyl chloride and methane were burned in a turbulent diffusion flame in a combustion wind tunnel with a coflow of air. Reynolds numbers were varied from 3500 to 7200. A water- cooled sampling probe was used to obtain gas samples from within the flame at a number of locations and at various Reynolds numbers. The postflame gases and particulate matter were trapped above the flames with sorbent tubes and filters. The samples were desorbed and analyzed for aromatic species and other trace products of incomplete combustion. Destruction of the methyl chloride was essentially complete for all the Reynolds numbers that were studied. Small amounts of low molecular weight chlorinated compounds were fOUnd within the flame and in the postflame gases. The major chlorinated species in the postflame gases was chloronaphthalene. Low Reynolds number flames were found to Yield larger amounts of aromatic and chlorinated aromatic species than the high Reynolds number flames. Fluoranthene was present in greater amounts on the soot particles at lower Reynolds numbers, suggesting that the rate of mixing of reactants could have an impact on the toxicity of the combustion byproducts. Combustion of chlorinated wastes can lead to the formation of hazardous byproducts. Rates of mixing of fuel and air in combustion systems can have an impact on the composition of the byproducts. Methyl chloride and methane were burned in a turbulent diffusion flame in a combustion wind tunnel with a coflow of air. Reynolds numbers were varied from 3500 to 7200. A water-cooled sampling probe was used to obtain gas samples from within the flame at a number of locations and at various Reynolds numbers. The postflame gases and particulate matter were trapped above the flames with sorbent tubes and filters. The samples were desorbed and analyzed for aromatic species and other trace products of incomplete combustion. Destruction of the methyl chloride was essentially complete for all the Reynolds numbers that were studied. Small amounts of low molecular weight chlorinated compounds were found within the flame and in the postflame gases. The major chlorinated species in the postflame gases was chloronaphthalene. Low Reynolds number flames were found to yield larger amounts of aromatic and chlorinated aromatic species than the high Reynolds number flames. Fluoranthene was present in greater amounts on the soot particles at lower Reynolds numbers, suggesting that the rate of mixing of reactants could have an impact on the toxicity of the combustion byproducts.
- Yang, Gosu,Jones, A. Daniel,Kennedy, Ian M.
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p. 1265 - 1268
(2007/10/03)
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- Iron (III) perchlorate: A novel reagent for functional group as well as ring transformations in organic synthesis
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Oxidative dimerization of some aromatic hydrocarbons, diphenylacetylene and diphenyl amine, selective oxidation of thiols to disulfides, and transformation of 1,5-cyclooctadiene to the corresponding bicyclooctane derivatives through trans-annular reactions have been achieved using iron (III) perchlorate(ITP).
- Kumar, Baldev,Parmar, Anupama,Rajpal, Anita,Kumar, Harish
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p. 593 - 595
(2007/10/03)
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- Formation of C60 radical cation in iron(III)-exchanged zeolite Y
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When C60 is introduced into the Fe3+-exchanged zeolite Y sample, an intense ESR signal at g = 2.0027 is observed. The ESR signal is due to the formation of C60 radical cation (C60?+), since the signal intensity increases with an increase in the amount of Fe3+ loaded in the zeolite. Addition of perylene into the C60?+-zeolite system results in electron transfer from perylene to C60?+ to produce perylene radical cation accompanied by the disappearance of C60?+.
- Fukuzumi, Shunichi,Suenobu, Tomoyoshi,Urano, Tsutomu,Tanaka, Keiko
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p. 875 - 876
(2007/10/03)
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- Process for the preparation of peryleneimides, novel di-, tri- and tetrachromophoric perylene dyes and their use
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Di-, tri- and tetrachromophoric perylene-3,4:9,10-tetracarboxylic acid imides of the formula I STR1 in which A is, for example, 1,4-phenylene, R is 1-hexylheptyl and m is 2, are readily accessible by reaction of a perylene-3,4:9,10-tetracarboxylic acid monoanhydride monoimide with 1,4-diaminobenzene-bisformamide. The preparation process and also a specific process for the preparation of monochromic perylene-3,4:9, 10-tetracarboxylic acid bisimides are also claimed. These processes are particularly suitable for reaction of highly electron-rich aromatic amines, which cannot be reacted under conventional condensation conditions. The compounds according to the invention are suitable, for example, as colouring agents for melt coloration of high molecular weight organic material, for use in security printing, as fluorescence dyes for machine-readable markings, as laser dyes and for the production of printing toners, colour filters, organic photoreceptors, electroluminescence and photoluminescence elements or solar collectors.
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- Ternary solid solutions of 1,4-diketo-pyrrolopyrroles and quinacridones
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Temary solid solutions useful as pigments are disclosed. The ternary solid solutions result from incorporating a third component, which is a diketopyrrolopyrrole or quinacridone pigment, into the crystal lattice of the mixed crystal formed from equimolar amounts of two different diketopyrrolopyrrole pigments.
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- Investigation of the direct and indirect reduction processes of some disulfides by electrochemical means
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The free energy relationship for the reaction between aromatic radical anions A.- having about the same intrinsic barrier and three disulfides RSSR (diphenyl disulfide, dimethyl disulfide and di-tert-butyl disulfide) in N,N-dimethylformamide has been obtained. For each RSSR second-order rate constants were measured electrochemically in the interval 10-3-105 M-1 s-1 by changing the nature of A.- and thereby the driving force. In the case of diphenyl disulfide the standard potential ERSSR/RSSR.-? and the self-exchange reorganization energy λ(0) of the RSSR/RSSR.- couple could be extracted from the free energy relationship to values of -1.4 (±0.1) V vs. SCE and 65 kcal mol-1, respectively. This knowledge may be combined with the kinetic features of the heterogeneous reduction process of diphenyl disulfide to obtain, among other parameters, the standard heterogeneous rate constant. The cleavage rate constant kc of the corresponding radical anion was estimated from kinetic measurements to be about 5 × 108 s-1. No such information was accessible for the aliphatic disulfides due to a high self-exchange energy of the RSSR/RSSR.- couple but still a maximum value of kc could be determined at 2x108 s-1. The minimum values of ERSSR/RSSR.-? and λ(0) were estimated to be -1.9 V vs. SCE and 75 kcal mol-1 and -2.2 V vs. SCE and 75 kcal mol-1 for dimethyl disulfide and di-tert-butyl disulfide, respectively. ? Acta Chemica Scandinavica 1997.
- Bo Christensen, Torben,Daasbjerg, Kim
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p. 307 - 317
(2007/10/03)
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- Electron Transfer Reactions and Mobile Holes in Radiolysis of Squalane. Time-Resolved FDMR Study
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Fluorescence detected magnetic resonance (FDMR) is applied to study ion-molecule reactions in squalane (2,6,10,15,19,23-hexamethyltetracosane).Several time-resolved pulsed FDMR experiments are suggested to measure rate constants of scavenging by aromatic solutes.These constants vary from 5E8 to 1.6E9 mol-1 dm3 s-1.The ion-molecule reactions of radical cations are somewhat slower than reactions of radical anions.The scavenging of the alkane hole is significantly faster than ion-molecule reactions of molecular cations.The mobile hole decays on a time scale of several tens of nanoseconds.These FDMR results are in accord with our recent work on transient absorption spectroscopy in radiolysis of squalane.
- Shkrob, I. A.,Trifunac, A. D.
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p. 14681 - 14687
(2007/10/03)
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- C60 as a Photocatalyst of Electron-Transfer Processes: Reactions of Triplet C60 with Chloranil, Perylene, and Tritolylamine Studied by Flash Photolysis and FT-EPR
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Photoprocesses in benzonitrile solutions of C60 and chloranil (CA) have been studied by complementary techniques of nanosecond laser photolysis and Fourier transform EPR.Direct oxidation of 3C60 by CA is slow (k = (2.0 +/- 0.3)E7 M-1 s-1), consistent with the high oxidation potential of 3C60.However, the formation rate and yield of CA(1-) are much increased by addition of perylene (Pe) or tritolylamine (TTA) via the fast reactions 3C60 + Pe -> C60 + 3Pe, followed by 3Pe + CA -> Pe(1+) + Ca(1-), or 3C60 +TTA -> C60(1-) + TTA(1+), followed by C60(1-) + CA -> C60 + CA(1-).These reactions utilize the broad absorption and initial high triplet yield of C60, as well as the low oxidation potential of 3Pe or high reduction potential of 3C60, to catalyze efficient formation of CA(1-) and enhance separation of radicals.Triplet C60 also reacts with Pe by electron transfer, forming Pe(1+) and C60(1-) with rate one-third that of energy transfer.However, the Ca(1-) formed in the Pe-catalyzed reaction is strongly spin-polarized, indicating that it is formed primarily via the 3Pe pathway.The extinction coefficient of C60(1-) at 1080 nm is measured (ε = 18300 +/- 1100 M-1 cm-1) using the TTA reaction.
- Steren, Carlos A.,Willigen, Hans van,Biczok, Laszlo,Gupta, Neeraj,Linschitz, Henry
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p. 8920 - 8926
(2007/10/03)
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- High-Mobility Ions in Cyclohexane. A Transient Absorption Study
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Transient absorption kinetics in radiolysis of N2O-saturated cyclohexane has been studied (0.1 - 100 ns; 300 - 800 nm).The spectra indicate the involvement of at least three cations (ions I, II, and III), only one of them having abnormally high mobility.Ion II is probably the cyclohexene radical cation, and ion III might be the dimer olefin ion.These two ions absorb as much as ion I at 450 - 500 nm.While ion II and ion III are scavenged by ethanol and triethylamine with a rate constant of ca. 1E10 mol-1 dm3 s-1, the scavenging of ion I proceeds with rate constants of ca. 9E10 and 2.3E11 mol-1 dm3 s-1, respectively.The spectrum of ion I is similar to the spectrum of the radical cation of cyclohexane isolated in low-temperature matrices.We were not able to observe the absorption from ion I at delay times longer than 50 ns.A corresponding fast growth of the absorption from solute radical cations of pyrene and perylene was observed.The data (simulated using continuum-diffusion and Monte Carlo approaches) indicate that the scavenging constant is ca. 4E11 mol-1 dm3 s-1; the lifetime of the precursor of the aromatic radical cations is ca. 30 ns.This short lifetime cannot be explained by a reaction with radiolytic products or by homogeneous recombination, and it seems to be incompatible with identification of the long-lived high-mobility ions observed in conductivity experiments as the radical cation of cyclohexane.A mechanism in which the mobile radical cation is in equilibrium with a normally-diffusing ion is examined in an attempt to resolve this conundrum.
- Shkrob, I. A.,Sauer, M. C.,Trifunac, A. D.
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p. 7237 - 7245
(2007/10/03)
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- Synthesis of Perylene-3,4-dicarboximides - Novel Highly Photostable Fluorescent Dyes
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Perylene-3,4-dicarboximides 2 are obtained by a decarboxylizing condensation of moderately sterically hindered primary amines with perylene-3,4,9,10-tetracarboxylic 3,4:9,10-bisanhydride (3) in the presence of water.Perylene-3,4-dicarboxylic anhydride (4) is prepared by hydrolysis of the imides with KOH in tert-butyl alcohol.The anhydride may be condensed with any primary amine to the corresponding imide.The imides are highly fluorescent and very photostable dyes. - Key Words: Fluorescent dyes/Pigments/Perylenes/Carboximides
- Feiler, Leonhard,Langhals, Heinz,Polborn, Kurt
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p. 1229 - 1244
(2007/10/02)
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- Evidences for the generation of α-alkoxy and α-alkylthioalkyl radicals upon reduction of α-functionalized alkyl phenyl sulfones. Investigation of the reduction mechanism by electrochemistry
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The mechanism of single electron transfer reduction of α-halo-, α-alkoxy-, or α-alkylthioalkyl phenyl sulfones is investigated using cyclic or steady-state voltammetry.This study provides strong evidence that some of these sulfones can be used to generate free radicals at potentials at which they cannot be reduced.Further confirmation is obtained by indirect electrolysis.Finally, redox catalysis allows determination of standard potentials and cleavage rate constants for most of the sulfone radical anions.Keywords: sulfones / single electron transfer / electrochemical reduction / alkoxyalkyl radicals / alkylthioalkyl radicals
- Amatore, C.,Bayachou, M.,Bontejengout, F.,Verpeaux, J. N.
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p. 371 - 381
(2007/10/02)
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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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- Photoionization and Ensuing Ion-Molecule Reactions of Polycyclic Aromatic Hydrocarbons in Alkane and Alcohol Solutions
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A common reaction pathway involving ion-molecule reactions of excited ions is indicated for a series of polycyclic aromatic hydrocarbons photoionized using intense pulsed excimer lasers (248 and 308 nm).The overall yields of free electrons and free aromatic radical cations created by two-photon ionization are measured by laser flash photolysis in cyclohexane and in 2-propanol solutions.The electron yields increase with increasing photon energies and photon flux, but the yield of radical cation is found to decrease with increasing photon flux.Photoproducts derived from aryl and solvent radicals are observed and quantified by GC and GC-MS, and their yields increase with increasing photon energy and photon flux.The diminished yield of radical ions at higher photon flux suggests an alternate higher energy reaction pathway for the radical cation.While aryl radical cations are relatively unreactive, an excited aryl radical cation could protonate the surrounding solvent, leading to aryl radical formation (AH.+* +RH -> A. + RH2+).Solvent radical formation would then result from hydrogen atom abstraction by aryl radicals.Product studies support this ion-molecule reaction pathway and exclude alternate mechanisms involving neutral excited state homolysis.
- Liu, Andong,Loffredo, David M.,Trifunac, Alexander D.
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p. 3791 - 3799
(2007/10/02)
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- Electrophilic substitution of two monohomoperylenes and perylene
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Various types of electrophilic substitution of monohomoperylene (1) and its 11,11-difluoro derivative (2) have been studied, viz, bromination, nitration, acylation, formylation and sulfonation.Bromination with N-bromosuccinimide (NBS) of 1 in dichloromethane leads to initial substitution mainly at the α position 2 and 10, i.e., of the annuleno moiety, followed by further substitution of the β positions 4 and 8 of the same moiety, and of the α positions 2' and 10' of the naphthaleno moiety.Reaction of 1 with 5.0 mol-equiv. of NBS yields 2,4,8,10,2'-pentabromo-1 in 46percent yield.Sulfonation of 1 with SO3 in dichloromethane using 1.2 mol-equiv. of dioxane as reactivity moderator leads to the formation of 1-2-sulfonic acid (1-2-S), 1-2,10-S2, and the intermediate ? complex 6.Sulfonation of the 11,11-difluoro derivative 2 leads to the formation of 2-2-S, 2-2,10-S2 and 2-2,10-disulfonic anhydride (7), together with small amounts of 2-2,2'-S2 or/and 2-2,10'-S2.The other types of electrophilic substitution of 1 and 2 studied were found to proceed similarly, in that the initial substitution occurs at the 2-position and the subsequent one at the 10-position, i.e., peri to the primarily introduced substituent.The chemical behaviour (i.e., the substitution pattern and relative reactivity) of the two monohomoperylenes 1 and 2 have been compared with that of 1,6-methanoannulene (3), its 11,11-difluoro derivative (4), and perylene (5).For example, the sulfonation reactivity ratio of the naphthalene to the annuleno moiety is significantly greater for 2 than 1, as predicted on the basis of the higher sulfonation reactivity of 3 compared to 4.
- Cerfontain, Hans,Koeberg-Telder, Ankie,Lerch, Ulrike
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p. 584 - 594
(2007/10/02)
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- Solvent Effects on Photoinduced Electron-Transfer Reactions
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Dependence of the fluorescence-quenching rate constant kq, effective quenching distance rq, and free radical yield ΦR on the free enthalphy change ΔGf of full electron transfer has been studied in dichloromethane by using anthracenecarbonitrile as electron-accepting fluorescers and amino- and methoxybenzenes as electron-donating quenchers.On the basis of the present data in dichloromethane and the previous data in acetonitrile, the solvent effects on the electron-transfer fluorescence-quenching mechanism and on the back electron-transfer reaction within the geminate radical ion pairs are elucidated.
- Niwa, Taeko,Kikuchi, Koichi,Matsusita, Noriyuki,Hayashi, Michiko,Katagiri, Tomoharu,et al.
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p. 11960 - 11964
(2007/10/02)
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- Effect of Charge Distribution upon Condensed-Phase Electron Transfer between Isotopic Isomers
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EPR analysis of the anion radicals resulting from the partial potassium reduction of mixtures of perdeuteriated and perprotiated polyaromatics (*R and R, respectively) in tetrahydrofuran shows that the equilibrium constant for the reaction R-radicalanion,M+ + *R -> - R + *R-radicalanion,M+ is less than unity but that it is closer to unity for systems with large amounts of charge density on the ring juncture carbons.These EPR results predict that a separation of anion radical from neutral molecule would effect an isotopic separation.Removal of the THF leaves a solid mixture of neutral polyaromatic and the potassium anion-radical salt.Subsequent dissolution or sublimation of the neutral polyaromatics from the anion radical yields a mixture that is enriched in the heavy isotopic isomer, and reoxidation of the anion radical with iodine yields a mixture that is depleted in the heavy isotopic isomer.The room-temperature equilibrium constants obtained from these physical separations are not as large as those measured in solution due to lattice effects in the solid state.
- Stevenson, Gerald R.,Sturgeon, Bradley E.
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p. 4090 - 4093
(2007/10/02)
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- Pulse Radiolysis Study of Ion Pairing of Diphenylpolyene Radical Anions with Tetrabutylammonium and Sodium Cations in Tetrahydrofuran
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Pulse radiolysis of tetrahydrofuran (THF) solutions of all-trans α,ω-diphenyl-substituted polyenes, such as 1,4-diphenylbuta-1,3-diene, 1,6-diphenylhexa-1,3,5-triene and 1,8-diphenylocta-1,3,5,7-tetraene, has been undertaken in the absence and presence of Bu4NPF6 and NaBPh4.In the presence of the salts, the absorption maxima of the diphenylpolyene radical anions are shifted to shorter wavelengths by ion pairing with Bu4N+ and Na+ as well as that of the trans-stilbene radical anion previously investigated.When Ph(CH=CH)nPH.- (n=1-4) is paired with Bu4N+, the magnitude of the spectroscopic shift is larger for n=2-4 than for n=1.On the other hand, the magnitude of the spectroscopic shift due to the ion pairing with Na+ decreases with increasing n and becomes very small in the case of n=3 or 4.The decay of the radical anions, which is due to neutralization reactions with THF(H+), is retarded by the addition of the salts.The retarding effect of the salts is attributed to the ion pairing of the reactant ions with the counterions derived from the salts.In acetonitrile solution the absorption spectra and the decay rates of the radical anions are not affected by the addition of the salts, demonstrating that the ion pairing is not important in such a polar solvent.Results for the radical anions of pyrene, perylene and triphenylethylene are presented for the sake of comparison.The appreciable spectroscopic shift due to the ion pairing with the large Bu4N+ ion was found to be characteristic of the diphenylpolyene radical anions.
- Aoyama, Takahisa,Yamamoto, Yukio,Hayashi, Koichiro
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p. 3353 - 3358
(2007/10/02)
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- Electrochemical Measurements of Rate Constants for the Electron Transfer Reaction To Sterically Hindered Alkyl Halides
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Rate constants (k1) have been measured for electron transfer from different electron donors to t-butyl chloride, neopentyl bromide, exo-norbornyl bromide, isobornyl bromide, bornyl bromide and adamantyl bromide.The electron donors are typically anion radicals of aromatic or heteroaromatic compounds, where the unpaired electron is delocalized over a large ?-electron system.Curves showing the relationship between the logarithm of k1 and the potential of the electron donor are also included.Rate constants have been measured for the substitution reaction between the anion of 1,4-dihydro-4-methoxycarbonyl-1-methylpyridine (1-) and six alkyl halides.The rate constant (kSUB) for the substitution reaction of 1- on the alkyl halide is compared with kSET, which is the rate constant for an ET reaction of a hypothetical electron donor with the same standart potential as 1-/1..The kSUB/kSET values show that all these reactions are ET-like and the order of kSUB/kSET is the same as the order of steric hindrance of the alkyl halides.
- Daasbjerg, Kim,Pedersen, Steen U.,Lund, Henning
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p. 876 - 881
(2007/10/02)
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