129-00-0 Usage
Coal-tar chemical industrial products
Pyrene is one of the processing products of coal tar with the content in the coal tar being about 0.6 to 1.2% and is mainly concentrated in the anthracene oil fraction. Pyrene is a kind of solid aromatic compound with its molecule comprising of four benzene rings connected with each other. Pyrene has its molecular formula of C16H10, molecular weight of 202.26, melting point of 150 °C, boiling point of 393 °C and the density of 1.277g/cm3. Pyrene appears as pale yellow crystalline monoclinic tablets, insoluble in water and easily soluble in benzene, toluene, carbon disulfide, ether and other organic solvents. Pyrene is carcinogenic and can be converted to mutagenic 1-nitro-pyrene under the effect of nitrogen dioxide. The position 1 and position 6 of pyrene can easily react with electrophilic reagent as well as have oxidation and hydrogenation reaction. Pyrene can also have halogenation, nitration and sulfonation; mono-substitution occurs at the 3-position, di-substitution includes 3, 10 and 3, 8-position with 3, 10 being more frequent. Its oxidation can generate 3, 10-quinones and 3, 8-quinones which can further oxidized to generate 1, 4, 5, 8-naphthalene tetracarboxylic acid.
Pyrene can be used in the production of dyes such as indanthrone dyes and anthraquinone vat dyes. The extraction method of is: take the residuum or bitumen distillate oil produced from the distillation of the anthracene fractions as the raw material, perform distillation under reduced pressure, take the 390~400 ℃ fraction which contains about 40% of pyrene fraction, then use 25% of the coal tar solvent oil and 75% ethanol mixed solvent (the volume of the solvent: pyrene fraction: 1:12), and recrystallized for several times until qualified products are obtained.
Pyrene belongs to low toxicity compounds and has mild irritation effect on the skin, eyes and upper respiratory tract. Long-term inhalation can cause aglobulism and mild liver and kidney damage. Long-term exposure upon 3mg/m3~5mg/m3 can cause headaches, fatigue, loss of appetite, and being prone to excitable.
The above information is edited by the lookchem of Dai Xiongfeng.
Probing agent for determination of the fluidity of membrane lipid
Pyrene is a commonly used probe for determination of the fluidity of the membrane lipid with high quantum yield but shorter excited lifetime than DPH (1, 6-diphenyl a 1, 3, 5-triene), so it is not sensitive enough for determination of the slight change in the lipid fluidity and is suitable for system of greater mobility. The excitation wavelength of pyrene is 342nm and the emission wavelength is 383nm with the excitation and emission spectra overlapping significantly with each other. Pyrene mainly bound to the hydrocarbon chain of the membrane lipid. Once a monomer formed via the binding between a pyrene molecule to lipid molecule had been excited by light, it move and be close to another pyrene molecule which has not been excited yet via lateral diffusion motion, forming collision compounds namely excitation dimer. The efficiency for the formation of the excitation dimer depends on the concentration of pyrene binding to the membrane lipid as well as the viscosity of the medium surrounding the pyrene. When the concentration and temperature of pyrene becomes stable, the ratio of the fluorescence intensity between monomer and dimer will decrease with the increasing viscosity of the medium surrounding the pyrene, namely pyrene, based on the ratio of the fluorescence of dimer to monomer, can reflect the lateral diffusion rate of the lipid molecule. High medium viscosity will cause small lateral diffusion rate and small liquidity.
Reference: Editor: Huishan Liu, Binxue Liu & Zedai Fang; Reviwer: Shuyun Xu & Chuanggeng Ma; English-Chinese dictionary of pharmacology.
Chemical Properties
Different sources of media describe the Chemical Properties of 129-00-0 differently. You can refer to the following data:
1. It appears as light yellow monoclinic crystal. It is insoluble in water, easily soluble in ether, carbon disulfide, benzene and toluene.
2. pale yellow to yellow-greenish crystals or chunks
3. Pyrene is a colorless crystalline solid when
pure or pale yellow plates (impure). Polycyclic aromatic
hydrocarbons (PAHs) are compounds containing multiple
benzene rings and are also called polynuclear aromatic
hydrocarbons. Solids and solutions have a Blue fluores-
cence (Merck Index).
Uses
Different sources of media describe the Uses of 129-00-0 differently. You can refer to the following data:
1. It can be used as raw material of organic synthesis. For example, it can be used for production of 1, 4, 5, 8-naphthalene tetracarboxylic acid via oxidation. It can be applied to dyes, synthetic resins and plastics; it can also be used for the manufacturing of vat dye Brilliant Orange GR and various kinds of other dyes. Moreover, it can also be used for the manufacturing of pesticides and plasticizers.
2. Pyrene occurs in coal tar. Also obtained by the destructive hydrogenation of hard coal. Found in wastewater in aquatic environments, and possesses genotoxic characteristics relating to estrogenic/andr
ogenic, antiestrogenic and antiandrogenic activity.
3. Pyrene and its derivatives are used commercially to make?dyes?and dye precursors, for example?pyranine?and naphthalene-1,4,5,8-tetracarboxylic acid. It is used as a probe to determine solvent environments and fluorescence spectroscopy.
4. Pyrene may be used as an analytical reference standard for the quantification of the analyte in environmental tobacco smoke samples using high-performance liquid chromatography technique.
Production method
Pyrene is mainly presented in the distillates of coal tar pitch. Send the asphalt for vacuum distillation under medium temperature; at the same time, directly send a small amount of the overheated steam to the distillation vessel; take the narrow fraction of pyrene and then use the mixed solution of solvent oil and ethanol or a mixed solution of benzene and solvent oil for recrystallization to obtain industrial pyrene with purity of 95%.
Physical properties
Colorless solid (tetracene impurities impart a yellow color) or monoclinic prisms crystallized from
alcohol. Solutions have a slight blue fluorescence.
Production Methods
There is no commercial production or known use for this
compound. Pyrene has been used as starting material for the
synthesis of benzo[a]pyrene.
Definition
Different sources of media describe the Definition of 129-00-0 differently. You can refer to the following data:
1. A condensed ring hydro-
carbon.
2. A solid aromatic compound whose molecules consist
of four benzene rings joined together. It is
carcinogenic.
General Description
Colorless solid, solid and solutions have a slight blue fluorescence. Used in biochemical research.
Air & Water Reactions
Insoluble in water.
Reactivity Profile
Pyrene reacts with nitrogen oxides to form nitro derivatives. Pyrene also reacts with 70% nitric acid.
Hazard
A questionable carcinogen, absorbed by
skin.
Health Hazard
Different sources of media describe the Health Hazard of 129-00-0 differently. You can refer to the following data:
1. Pyrene is a carcinogenic agent and is absorbed by the skin. It is a skin irritant, a suspected mutagen, and an equivocal tumor-causing agent. Workers exposed to 3 to 5 mg/m3 of Pyrene exhibited some teratogenic effects. Pyrene is a polycyclic aromatic hydrocarbon (PAH). The acute toxicity of pure PAHs appears low when administered orally or dermally to rats or mice. Human exposure to PAHs is almost exclusively via the gastrointestinal and respiratory tracts, and approximately 99 percent is ingested in the diet. Despite the high concentrations of Pyrene to which humans may be exposed through food, there is currently little information available to implicate diet-derived PAHs as the cause of serious health effects.
2. Inhalation of its vapors or ingestion causedirritation of the eyes, excitement, and musclecontraction in rats and mice. An oral LD50value in mice has been reported as 800 mg/kg.Studies on experimental animals do not giveevidence of carcinogenicity. Skin tumors,however, have been reported in mice (NIOSH1986). Pyrene tested negative to a histidinereversion–Ames test and other mutagenictests.
Fire Hazard
When heated to decomposition, Pyrene emits acrid smoke and fumes.
Safety Profile
Poison by inhalation. Moderately toxic by ingestion and intraperitoneal routes. A sh irritant. Questionable carcinogen with experimental tumorigenic data. Human mutation data reported. When heated to decomposition it emits acrid smoke and irritating fumes.
Synthesis
The content in high temperature tar is about 1.2% ~ 1.8%, which is prepared by separation and purification. Using anthracene oil as raw material, vacuum distillation, extraction, recrystallization and purification. The residue of distilled anthracene oil above 360 ℃ is used as raw material, the pyrene fraction is cut by distillation, benzene is used as solvent, washed with concentrated sulfuric acid, the base and unsaturated compounds are removed, and then the pure product is recrystallized with solvent oil. It can also be extracted from tobacco. Pyrene mainly exists in the distillate of coal tar pitch. The medium temperature asphalt is distilled under reduced pressure, and a small amount of direct superheated steam is introduced into the distillation kettle to cut the narrow fraction of pyrene, and then recrystallized with the mixed solution of solvent oil and ethanol or the mixed solution of benzene and solvent oil to obtain industrial pyrene with a purity of 95%.
Potential Exposure
Pyrene is used as an industrial chemi-
cal and in biochemical research.
Carcinogenicity
Pyrene was inactive as a tumor initiator. Based on
inadequate animal data and no human data, the IARC
classified pyrene as group 3, not classifiable as to its
carcinogenicity to humans, and IRIS classified pyrene
as a class D compound. Pyrene is present as a major
component of the total content of PAHs in the environment.
Exposure occurs primarily through tobacco smoke,
inhalation of polluted air, and by ingestion of food and
water.
Source
Detected in groundwater beneath a former coal gasification plant in Seattle, WA at a concentration of 180 μg/L (ASTR, 1995). Detected in 8 diesel fuels at concentrations ranging
from 0.16 to 24 mg/L with a mean value of 5.54 mg/L (Westerholm and Li, 1994). Identified in
Kuwait and South Louisiana crude oils at concentrations of 4.5 and 3.5 ppm, respectively
(Pancirov and Brown, 1975).
Based on laboratory analysis of 7 coal tar samples, pyrene concentrations ranged from 900 to
18,000 ppm (EPRI, 1990). Detected in 1-yr aged coal tar film and bulk coal tar at concentrations
of 2,700 and 2,900 mg/kg, respectively (Nelson et al., 1996). Lehmann et al. (1984) reported a
pyrene concentration of 125 mg/g in a commercial anthracene oil. Identified in high-temperature
coal tar pitches used in electrodes at concentrations ranging from 4,500 to 34,900 mg/kg
(Arrendale and Rogers, 1981). Lee et al. (1992a) equilibrated eight coal tars with distilled water at
25 °C. The maximum concentration pyrene observed in the aqueous phase is 0.1 mg/L.
Nine commercially available creosote samples contained pyrene at concentrations ranging from
31,000 to 100,000 mg/kg (Kohler et al., 2000). Also detected in asphalt fumes at an average
concentration of 140.21 ng/m3 (Wang et al., 2001).
Schauer et al. (1999) reported pyrene in diesel fuel at a concentration of 64 μg/g and in a dieselpowered
medium-duty truck exhaust at an emission rate of 71.9 μg/km.
California Phase II reformulated gasoline contained pyrene at a concentration of 3.38 g/kg. Gasphase
tailpipe emission rates from gasoline-powered automobiles with and without catalytic
converters were approximately 4.28 and 160 μg/km, respectively (Schauer et al., 2002).
Schauer et al. (2001) measured organic compound emission rates for volatile organic
compounds, gas-phase semi-volatile organic compounds, and particle-phase organic compounds
from the residential (fireplace) combustion of pine, oak, and eucalyptus. The respective gas-phase
and particle-phase emission rates of pyrene were 1.87 and 3.78 mg/kg of pine burned, 2.40 and
1.23 mg/kg of oak burned, and 2.70 and 0.585 mg/kg of eucalyptus burned.
Under atmospheric conditions, a low rank coal (0.5–1 mm particle size) from Spain was burned
in a fluidized bed reactor at seven different temperatures (50 °C increments) beginning at 650 °C.
The combustion experiment was also conducted at different amounts of excess oxygen (5 to 40%)
and different flow rates (700 to 1,100 L/h). At 20% excess oxygen and a flow rate of 860 L/h, the
amount of pyrene emitted ranged from 29.9 ng/kg at 700 °C to 402.9 ng/kg at 750 °C. The greatest
amount of PAHs emitted were observed at 750 °C (Mastral et al., 1999).
Drinking water standard: No MCLGs or MCLs have been proposed by the U.S. EPA (2000).
Environmental fate
Biological. When pyrene was statically incubated in the dark at 25 °C with yeast extract and
settled domestic wastewater inoculum, complete degradation was demonstrated at the 5 mg/L
substrate concentration after 2 wk. At a substrate concentration of 10 mg/L, however, only 11 and
2% losses were observed after 7 and 14 d, respectively (Tabak et al., 1981).
Soil. The reported half-lives for pyrene in a Kidman sandy loam and McLaurin sandy loam are
260 and 199 d, respectively (Park et al., 1990).
Plant. Hückelhoven et al. (1997) studied the metabolism of pyrene by suspended plant cell
cultures of soybean, wheat, jimsonweed, and purple foxglove. Soluble metabolites were only
detected in foxglove and wheat. Approximately 90% of pyrene was transformed in wheat. In
foxglove, 1-hydroxypyrene methyl ether was identified as the main metabolite but in wheat, the
metabolites were identified as conjugates of 1-hydroxypyrene.
Photolytic. Adsorption onto garden soil for 10 d at 32 °C and irradiated with UV light produced
1,1′- bipyrene, 1,6-pyrenedione, 1,8-pyrenedione, and three unidentified compounds (Fatiadi,
1967). Microbial degradation by Mycobacterium sp. yielded the following ring-fission products:
4-phenanthroic acid, 4-hydroxyperinaphthenone, cinnamic acid, and phthalic acid. The
compounds pyrenol and the cis- and trans-4,5-dihydrodiols of pyrene were identified as
ring-oxidation products (Heitkamp et al., 1988).
Chemical/Physical. At room temperature, concentrated sulfuric acid will react with pyrene to
form a mixture of disulfonic acids. In addition, an atmosphere containing 10% sulfur dioxide
transformed pyrene into many sulfur compounds, including pyrene-1-sulfonic acid and
pyrenedisulfonic acid (Nielsen et al., 1983).
Shipping
UN3077 Environmentally hazardous substances,
solid, n.o.s., Hazard class: 9; Labels: 9-Miscellaneous haz-
ardous material, Technical Name Required.
Purification Methods
Crystallise pyrene from EtOH, glacial acetic acid, *benzene or toluene. Purify it also by chromatography of CCl4 solutions on alumina, with *benzene or n-hexane as eluent. [Backer & Whitten J Phys Chem 91 865 1987.] It can also be zone refined and purified by sublimation. Marvel and Anderson [J Am Chem Soc 76 5434 1954] refluxed pyrene (35g) in toluene (400mL) with maleic anhydride (5g) for 4days, then added 150mL of aqueous 5% KOH and refluxed for 5hours with occasional shaking. The toluene layer was separated, washed thoroughly with H2O, concentrated to about 100mL and allowed to cool. Crystalline pyrene was filtered off and recrystallised three times from EtOH or acetonitrile. [Chu & Thomas J Am Chem Soc 108 6270 1986, Russell et al. Anal Chem 50 2961 1986.] The material is free from anthracene derivatives. Another purification step involves passage of pyrene in cyclohexane through a column of silica gel. It can be sublimed in a vacuum and zone refined. The picrate has m 224o. [Kano et al. J Phys Chem 89 3748 1985, Beilstein 5 IV 2467.]
Incompatibilities
Pyrene Dust may form explosive mixture
with air. Incompatible with oxidizers (chlorates, nitrates,
peroxides, permanganates, perchlorates, chlorine, bromine,
fluorine, etc.); contact may cause fires or explosions. Keep
away from alkaline materials, strong bases, strong acids,
oxoacids, epoxides. Pyrene reacts with nitrogen oxides to
form nitro derivatives. It also reacts with 70% nitric
acid
Waste Disposal
Dissolve or mix the
material with a combustible solvent and burn in a chemical
incinerator equipped with an afterburner and scrubber.
All federal, state, and local environmental regulations must
be observed .
Check Digit Verification of cas no
The CAS Registry Mumber 129-00-0 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 1,2 and 9 respectively; the second part has 2 digits, 0 and 0 respectively.
Calculate Digit Verification of CAS Registry Number 129-00:
(5*1)+(4*2)+(3*9)+(2*0)+(1*0)=40
40 % 10 = 0
So 129-00-0 is a valid CAS Registry Number.
InChI:InChI=1/C16H10/c1-3-11-7-9-13-5-2-6-14-10-8-12(4-1)15(11)16(13)14/h1-10H
129-00-0Relevant articles and documents
Surfactant-Concentration Effects in Photoinduced Electron Transfer from Pyrene to Cupric Ions in Sodium Dodecyl Sulfate Micelle Solutions
Nakamura, Takashi,Kira, Akira,Imamura, Masashi
, p. 3435 - 3441 (1984)
The decay of pyrene fluorescence and the quantum yield of pyrene cations were measured by using the laser photolysis method in sodium dodecyl sulfate (SDS) micelle solutions containing both pyrene and cupric dodecyl sulfate at 40 deg C.The decay curve of the pyrene fluorescence deviates from the first-order rate law at SDS concentrations below 0.2 M, as alredy known, but becomes first order at higher SDS concentrations.The rate shows incontinuity between 0.2 and 0.5 M SDS.The cation quantum yield remarkably increases with the SDS concentration: For 10 mM of cupric ion, the quantum yields were 0.25 and 0.60 at SDS concentrations of 0.05 and 0.8 M, respectively.These results can be explained in terms of involvement of large rodlike micelles in which the portion of the net electron transfer in quenching is larger than in usual spherical micelles.
THE ALKALI METAL REDUCTION OF PYRENE-STRUCTURAL AND PREPARATIVE ASPECTS
Schnieders, C.,Muellen, K.
, p. 1701 - 1712 (1984)
Reduction of pyrene with alkali metals yields the corresponding dianion salts.The solvents, counterion and temperature must be carefully selected since side reactions such as protonation (e.g. in liquid ammonia) or cleavage of the etheral solvent occur readily.Moreover, the spectroscopic characterization of the dianion is complicated by rapid electron transfer processes.There is no experimental evidence for distorted dianion structures or for further reduction of pyrene toward a tetraanion.Knowledge of the ionic pi-structures is essential for an understanding of reductive alkylation processes.
Photoionization of 10-methylphenothiazine, N,N,Na?2Na?2-tetramethylbenzidine, and pyrene in Cr-AlMCM-41 molecular sieves
Sinlapadech, Sunsanee,Koodali, Ranjit,Krishna,Kevan, Larry
, p. 6251 - 6257 (2002)
Photoionization of 10-methylphenothiazine (PC1), N,N,Na?2,Na?2-tetramethylbenzidine (TMB), and pyrene (Py) impregnated into mesoporous AlMCM-41 ion-exchanged with Cr(III), as an electron acceptor, to give Cr-AlMCM-41 was investigated. Cation radicals (PC1a?￠+, TMBa?￠+, Pya?￠+) are produced by 320 nm light at room temperature and characterized by electron spin resonance (ESR) and UV-vis diffuse reflectance spectroscopy. The chromium ion concentration was varied from Si/Cr = 52 to 121. Cr-AlMCM-41 with the intermediate concentration of Si/Cr = 80 exhibits the greatest electron acceptor ability and shows the highest photoionization efficiency photoionized. The photoionization efficiency also depends on the type of photoionizable molecule impregnated into mesoporous Cr-AlMCM-41 with PC1 being the most efficiently photoionized. The calcination temperature used before impregnation controls the oxidation state of chromium ions to Cr3+ or Cr5+/Cr6+, which also affects the photoionization efficiency. Cr-AlMCM-41 with Cr5+ gives about 4 times higher photoionization efficiency than with Cr3+. Cr-AlMCM-41 is shown to be a promising heterogeneous host for the efficient formation of photoinduced cation radicals to achieve long-lived charge separation in solid-state systems.
Formation and decay of pyrene radical cation and pyrene dimer radical cation in the absence and presence of cyclodextrins during resonant two-photon ionization of pyrene and sodium 1-pyrene sulfonate
Hara, Michihiro,Tojo, Sachiko,Kawai, Kiyohiko,Majima, Tetsuro
, p. 3215 - 3220 (2004)
Formation and decay of pyrene radical cation and pyrene dimer radical cation during resonant two-photon ionizations (TPI) of pyrene (Py) and sodium 1-pyrene sulfonate (NaPySA) in the absence and presence of cyclodextrins were studied with visible and near IR transient absorption measurement using 355-nm laser flash photolysis technique. Ionization of Py and 1-pyrene sulfonate anion (PySA-) occurred within the laser flash (5 ns) to give Py radical cation (Py?+) and PySA- radical cation (Py ?+SA-) having Py?+ chromophore. Dimerizations of Py?+ and Py and of Py?+SA - and PySA- were observed to give the dimer radical cations (Py2?+ and Py2 ?+(SA-)2) based on time-resolved measurements of the charge resonance (CR) band. The TPI of PySA- was also examined in the presence of β- and γ-cyclodextrins (βCD and γCD, respectively). Py2?+(SA-) 2 in the cavity of two γCDs having fully overlapped structure showed the CR band around 1700 nm, while Py2 ?+(SA-)2 in the cavity of two βCD having partially and fully overlapped structures indicated the CR bands around 1500 or 1700 nm, respectively. On the basis of formation and decay rates of Py2?+(SA-)2, bimolecular formation of Py2?+(SA-)2 and the neutralization are inhibited in the cavities of CDs. Selective formation of the fully overlapped structure of Py2?+(SA -)2 in the cavity of two γCDs within a laser flash is explained by direct TPI of two PySA-s with the parallel structure of two Py chromophores in two PySA-s in the cavity of two γCDs.
Laser-Induced Photoionization of Two-Electron-Reduced Viologen
Usui, Satoshi,Inoue, Hiroshi,Ishida, Hitoshi,Ohkubo, Katsutoshi
, p. 2089 - 2092 (1993)
Laser photolysis of two-electron-reduced 1,1'-bis(3-sulfonatepropyl)-4,4'-bipyridinium (PSV2-) produced by the reduction of PVS0 with Na2S2O4 in the cationic micelles of hexadecyltrimethylammonium chloride induced the photoionization of PVS2- to generate comparable amounts of PVS-. and hydrated electrons.Pyrene with a considerably negative potential of -2.09 vs.SCE was observed to be reduced in the system.
Reactivity of the 1-hydropyrenyl anion towards α,ω-dibromoalkanes
Dijk, Joost T. M. van,Lugtenburg, Johan,Cornelisse, Jan
, p. 1489 - 1496 (1995)
The reactivity of the 1-hydropyrenyl mono-anion (1-) towards 1,2-dibromoethane, 1,3-dibromopropane and 1,4-dibromobutane has been examined.Six novel products were isolated from these reactions and characterised: spiro (2), 1,3a-dihydro-1,3a-ethanopyrene (3), 9,10,11, 11a-tetrahydro-8bH-cyclopentapyrene (4), 2,3,3a,12a-tetrahydro-1H-cyclopentapyrene (5), 3a-(3-bromopropyl)-3,3a-dihydropyrene (6) and 8b,9,10,11,12,12a-hexahydrobenzolpyrene (7).The formation of these products could be rationalised by initial attack of the dibromoalkane at positions 3a and 5 of 1-.Deprotonation of the initial ω-bromoalkyldihydropyrenes leads to intramolecular alkylation, the course of which depends on the length of the alkyl chain.Attempts to aromatize the products resulted, except in the case of 5, in the fully aromatic pyrene derivatives cyclopentapyrene, benzopyrene, pyrene and the new cyclopenta-fused pyrene derivative, 10,11-dihydro-9H-cyclopentapyrene (9).
Electroreduction of 3-bromopyrene in DMF. A new organic electrochemical oscillator
Jaworski, Jan S.,Leszczynski, Piotr,Pawlowski, Slawomir
, p. 1715 - 1721 (1996)
The reduction of 3-bromopyrene in DMF at a mercury electrode for scan rates lower than 0.1 V s-1 is accompanied by a slow adsorption of an intermediate, resulting in a catalytic behaviour. The current oscillations take place in a region of the negative faradaic impedance.
Dynamics of a supramolecular capsule assembly with pyrene
Tang, Hao,De Oliveira, Carla Santos,Sonntag, Gage,Gibb, Corinne L. D.,Gibb, Bruce C.,Bohne, Cornelia
, p. 5544 - 5547 (2012)
Water-soluble octaacid cavitands (OAs) form dimeric capsules suitable for guest incorporation. Our studies reveal that the mechanism of pyrene (Py) binding involves the rapid (1 ms) formation of the Py?OA complex followed by slower binding with the second OA. The dissociation of the capsular OA?Py?OA complex occurs with a lifetime of 2.7 s, which is 5 orders of magnitude slower than the microsecond opening/closing ("breathing") previously observed to provide access of small molecules to the encapsulated guest. These different dynamics of the capsules have a potential impact on how the chemistry of included guests could be altered.
Phototransformations of environmental contaminants in models of the aerosol: 2 and 4-Nitropyrene
García-Berríos, Zulma I.,Arce, Rafael,Burgos-Martínez, Melanie,Burgos-Polanco, Natalia D.
, p. 131 - 140 (2017)
A comparative photochemical study of 2- and 4-nitropyrene (2- and 4-NO2Py) in different organic solvents was performed in order to provide information on the fate of these contaminants in models of the atmospheric aerosols. The isomers presented small photodegradation yields, 10?4–10?5 for 4-NO2Py and 10?5–10?6 for 2-NO2Py, demonstrating the low reactivity of the excited states and intermediate species that participate in their photodegradation. Photoproducts such as 4,5-pyrenedione, 4-hydroxypyrene, aminopyrene and pyrene were identified during the irradiation of 4-NO2Py. Substantial differences were observed in the photodegradation yields, and type and relative yields of the photoproducts of the 2-NO2Py and 4-NO2Py when compared to those of 1-NO2Py. These differences were related with the orientation of the nitro group and with differences in intersystem crossing rates which affect the yields of the pyrenoxy radical (PyO) and of the (π,π*) triplet state, principal precursors in their photodegradation. The smallest photodegradation yield was for 2-NO2Py due to the lack of interaction between the nitro group and the aromatic moiety thus resulting in a low yield of formation of the PyO radical. In the presence of O2, the photodegradation quantum yields of 4-NO2Py were reduced in all solvents due the quenching of the (π,π*) triplet state, and 4-aminopyrene was not observed thus demonstrating that its formation occurs from this state. These results suggest that in atmospheric aerosols containing an organic liquid-like layer, the nitropyrene isomers will show low photoreactivity resulting in an increase in their residence time in the atmosphere. An increase in reactivity is expected when the excited nitropyrenes are nearby substances with hydrogen donor capacities such as phenols. The photoproducts formed in the transformation could increase the toxicity of the particulate matter in the atmosphere.
Photophysical Properties of Pyrene in Zeolites: A Direct Time-Resolved Diffuse Reflectance Study of Pyrene Anion Radicals in Zeolites X and Y
Liu, Xinsheng,Iu, Kai-Kong,Thomas, J. Kerry
, p. 7877 - 7884 (1994)
The formation of pyrene anion radicals (Py.-) in the supercage of different alkali-ion-exchanged zeolites X and Y was studied using direct time-resolved diffuse reflectance techniques.Many factors such as the Si/Al ratio, the nature of charge balancing cations, the preactivation temperature, the pyrene loading, the state of hydration, and the nature of the surfaces (external versus internal) were examined in order to understand the formation and stabilization of Py.- in these samples, and also the mechanism of the photoinduced electron transfer processes.The results show that photoinduced electron transfer does not occur from pyrene to pyrene in the zeolites but occurs between pyrene molecule and the acidic and basic sites of the zeolites.The basic sites of the zeolites, responsible for the formation of Py.-, are framework oxygen.Stabilization of Py.- requires the special environment of the zeolite supercage; it is noteworthy that Py.- cannot be formed on the external surface of a zeolite.The formation of Py.- in the different alkali-ion-exchanged zeolites X- and Y follows the order of basicity of these samples, which is calculated using the Sanderson electronegativity equalization principle.Preactivation of the samples at temperatures of 350, 550, and 750 deg C does not affect the ratio of the anion to cation, Py.-/Py.+, yields.Posthydration of the samples alters the photophysical processes in the zeolites and gives rise to an increase in the yield of Py.-.At low light intensities, the photoinduced electron transfer follows a single-photon increase in the yield of Py.-.At low light intensities, the photoinduced electron transfer follows a single-photon mechanism.
