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Tomašević A, Mijin D, Radišić M, Prlainović N, Cvijetić I, Kovačević DV, Marinković A. Photolysis of insecticide methomyl in various solvents: An experimental and theoretical study. J Photochem Photobiol A Chem 2020. [DOI: 10.1016/j.jphotochem.2020.112366] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Zeng X, Qu R, Feng M, Chen J, Wang L, Wang Z. Photodegradation of Polyfluorinated Dibenzo-p-Dioxins in Organic Solvents: Experimental and Theoretical Studies. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2016; 50:8128-8134. [PMID: 27380414 DOI: 10.1021/acs.est.6b02682] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Eighteen polyfluorinated dibenzo-p-dioxins (PFDDs) were synthesized by pyrolysis of fluorophenols. Using a 500 W Xe lamp as the light source, the PFDDs photodegradation kinetics in n-hexane were investigated. The photolysis reactions obeyed the pseudo-first-order rate equation, and higher fluorinated PFDDs tended to photolyze more slowly. Theoretically calculated parameters reflecting the molecular structural properties were used to develop a new model of PFDDs photolysis rates. The results indicated that the substitution pattern for fluorine atoms and the C-O bond length were major factors in the photolysis of PFDDs. We selected octafluorinated dibenzo-p-dioxin (OFDD) as a representative PFDDs to explore the influence of solvent on the photolysis rate of PFDDs, and the results indicated that neither the polarity nor donor hydrogen of organic solvents are independent influencing factors. Mechanistic pathways for the photolysis of OFDD in n-hexane were first studied. The results indicated that photodegradation of OFDD produces octafluorinated dihydroxybiphenyls, octafluorinated phenoxyphenols, and fluorinated phenols. The major pathway for photodegradation of OFDD was C-O bond cleavage. Defluorination reactions did not occur during the photolysis process.
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Affiliation(s)
- Xiaolan Zeng
- State Key Laboratory of Pollution Control and Resources Reuse, School of Environment, Nanjing University , Jiangsu Nanjing 210023, PR China
- College of Chemistry and Chemical Engineering, Xinyang Normal University , Henan Xinyang 464000, PR China
| | - Ruijuan Qu
- State Key Laboratory of Pollution Control and Resources Reuse, School of Environment, Nanjing University , Jiangsu Nanjing 210023, PR China
| | - Mingbao Feng
- State Key Laboratory of Pollution Control and Resources Reuse, School of Environment, Nanjing University , Jiangsu Nanjing 210023, PR China
| | - Jing Chen
- State Key Laboratory of Pollution Control and Resources Reuse, School of Environment, Nanjing University , Jiangsu Nanjing 210023, PR China
| | - Liansheng Wang
- State Key Laboratory of Pollution Control and Resources Reuse, School of Environment, Nanjing University , Jiangsu Nanjing 210023, PR China
| | - Zunyao Wang
- State Key Laboratory of Pollution Control and Resources Reuse, School of Environment, Nanjing University , Jiangsu Nanjing 210023, PR China
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Elucidating photodehalogenation mechanisms of polychlorinated and polybrominated dibenzo-p-dioxins and dibenzofurans and Mg2+ effects by quantum chemical calculations. COMPUT THEOR CHEM 2014. [DOI: 10.1016/j.comptc.2014.03.024] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Wang S, Huang J, Yang Y, Yu G, Deng S, Wang B. Photodegradation of Dechlorane Plus in n-nonane under the irradiation of xenon lamp. JOURNAL OF HAZARDOUS MATERIALS 2013; 260:16-23. [PMID: 23747460 DOI: 10.1016/j.jhazmat.2013.04.034] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2013] [Revised: 03/30/2013] [Accepted: 04/23/2013] [Indexed: 06/02/2023]
Abstract
Photodegradation has been regarded as the main mechanism for the removal of many halogenated organic pollutants in the environment. The photodegradation of Dechlorane Plus (DP), an emerging contaminant taken worldwide concerns in recent years, was investigated under the irradiation of a xenon lamp. Rapid photodegradation was found under the irradiation of 200-750 nm light, while the degradation became much slower when the range of light wavelength changed to 280-750 nm. DP degradation followed the pseudo first-order kinetics. The quantum yields of 200-280 nm (UV-C) were about 2-3 orders of magnitude higher than 280-320 nm, and no yields can be detected in 320-750 nm range, in an agreement with the changing photodegradation rates with wavelength. The photodegradation products were identified as lower chlorinated DPs, implicating a mechanism of reductive dechlorination. No photoisomerization or solvent adducts were observed, and the difference of photodegradation rate between syn- and anti-DP isomers was negligible.
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Affiliation(s)
- Siwen Wang
- State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, POPs Research Center, Tsinghua University, Beijing 100084, PR China
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Bendig P, Vetter W. Photolytical transformation rates of individual polybrominated diphenyl ethers in technical octabromo diphenyl ether (DE-79). ENVIRONMENTAL SCIENCE & TECHNOLOGY 2010; 44:1650-1655. [PMID: 20121183 DOI: 10.1021/es903023m] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Polybrominated diphenyl ethers (PBDEs) are of environmental concern due to their persistence, potential to bioaccumulate, and possible toxic effects, especially for the lower brominated homologues. Reductive debromination under UV light has been identified as the main abiotic pathway for PBDE transformation. Although the kinetics and transformation products have been determined for individual PBDE congeners in different matrices, no effort has been made to determine the kinetics of these congeners when technical mixtures are exposed to UV light. We irradiated technical octabromodiphenyl ether (DE-79) in a perdeuterated solvent to determine the photolytic transformation kinetics of native PBDE congeners. Each deuterium that replaced bromine resulted in a shift to higher masses compared to the native congener, which was measured by gas chromatography with electron ionization mass spectrometry in the selected ion monitoring mode (GC/EI-MS-SIM). Tri-, tetra-, and pentabromodiphenyl ether products (BDE 28, BDE 47, BDE 49, BDE 99, BDE 100) could be proportioned to higher brominated precursors as a function of irradiation time. The kinetics of UV-irradiated single PBDE congeners matched well with results of previous studies of single congeners. However, when the same congeners were irradiated in the technical DE-79 mixture, their half-lives were longer by 20-160%. This study indicates that individually irradiated PBDE congeners behave differently than if present as a mixture. This result should be taken into account in models predicting the environmental fate of PBDEs and most likely also the mixtures of other contaminant groups.
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Affiliation(s)
- Paul Bendig
- Institute of Food Chemistry, University of Hohenheim, Garbenstrasse 28, D-70599 Stuttgart, Germany
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Mitoma Y, Kakeda M, Simion AM, Egashira N, Simion C. Metallic Ca-Rh/C-methanol, a high-performing system for the hydrodechlorination/ring reduction of mono- and poly chlorinated aromatic substrates. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2009; 43:5952-5958. [PMID: 19731703 DOI: 10.1021/es9004587] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We investigated the reduction of some substituted mono- and poly chlorobenzenes bearing functional groups such as methyl, methoxy, hydroxyl, and amino, under mild conditions (80 degrees C and magnetic stirring, for 2 h) using a system consisting of metallic calcium and methanol (as hydrogen donor system) and 5% wt. Rh/C (as hydrodechlorination/ring reduction catalyst). Hydrodechlorination easily took place for methoxy- and alkyl-chlorobenzenes, yielding the corresponding hydrodechlorinated compounds (57-76%) and affording as secondary reaction products the ring-reduced compounds (16-43%). Treatment of hydroxy- and amino-chlorobenzenes under the same conditions, respectively, gave corresponding hydrodechlorinated compounds (over 60%) along with the ring-reduced compounds. Results show that the reaction of substituted polychlorinated benzenes needs a longer reaction time (6 h), the transformation being nevertheless complete.
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Affiliation(s)
- Yoshiharu Mitoma
- Department of Environmental Sciences, Faculty of Life and Environmental Sciences, Prefectural University of Hiroshima, 562 Nanatsuka-Cho, Shobara City, Hiroshima 727-0023, Japan.
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Wang Z, Huang W, Fennell DE, Peng P. Kinetics of reductive dechlorination of 1,2,3,4-TCDD in the presence of zero-valent zinc. CHEMOSPHERE 2008; 71:360-8. [PMID: 17977573 DOI: 10.1016/j.chemosphere.2007.08.049] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2007] [Revised: 08/19/2007] [Accepted: 08/22/2007] [Indexed: 05/07/2023]
Abstract
Polychlorinated dibenzo-p-dioxins (PCDDs) are toxic and widespread persistent organic pollutants (POPs). Cost-effective technologies for destroying or detoxifying PCDDs are in high demand. The overall purpose of this study was to develop a zero-valent zinc based technology for transforming toxic PCDDs to less- or non-toxic forms. We measured the dechlorination rates of 1,2,3,4-tetrachlorodibenzo-p-dioxin (1,2,3,4-TCDD) in the presence of zero-valent zinc under aqueous conditions, identified the daughter compounds of the reaction, and constructed possible pathways for the reactions. The reaction rates of daughter compounds with zero-valent zinc were also measured independently. Our results showed that the zero-valent zinc is a suitable candidate for reducing PCDDs. Reductive dechlorination of 1,2,3,4-TCDD was stepwise and complete to dibenzo-p-dioxin (DD) mainly via 1,2,4-trichlorodibenzo-p-dioxin (1,2,4-TrCDD), 1,3-dichlorodibenzo-p-dioxin (1,3-DCDD), 1-chlorodibenzo-p-dioxin (1-MCDD) to DD and via 1,2,4-TrCDD, 2,3-dichlorodibenzo-p-dioxin (2,3-DCDD), 2-chlorodibenzo-p-dioxin (2-MCDD) to DD. In each separate system, the observed half-lives of 1,2,3,4-TCDD, 1,2,3-TrCDD, 1,2,4-TrCDD, 1,2-DCDD, 1,3-DCDD, 1,4-DCDD and 2,3-DCDD are 0.56, 2.62, 5.71, 24.93, 41.53, 93.67 and 169.06 h respectively. The tendency of rate constant follows TCDD>TrCDD>DCDD. Our results suggest that zero-valent zinc is a suitable candidate for rapidly reducing highly chlorinated PCDDs to less or non-chlorinated daughter products.
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Affiliation(s)
- Zhiyuan Wang
- Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Wushan, Guangzhou 510640, People's Republic of China
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Misaka Y, Abe T, Takeuchi K, Ohba K, Sawabe K, Shobatake K. Dechlorination/hydrogenation and destruction reactions of PCDDs in OCDD-added fly ash heated under vacuum. CHEMOSPHERE 2006; 65:419-26. [PMID: 16647100 DOI: 10.1016/j.chemosphere.2006.01.079] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2005] [Revised: 01/20/2006] [Accepted: 01/25/2006] [Indexed: 05/08/2023]
Abstract
Octachlorodibenzo-p-dioxin (OCDD)-added, pretreated fly ash was heated under vacuum at sample temperatures ranging from T(s)=450 to 650 K. The fly ash and liquid nitrogen-cooled trap samples were analyzed for DD/DF through OCDD/DF. The total amounts of DD through OCDD decrease with increasing T(s), which indicates that dechlorination/hydrogenation (DCH) reactions are not the only reaction channels. Reduction of toxic equivalent (TEQ) for PCDDs by more than 99% was achieved in the fly ash by the vacuum heat treatment at T(s)=650 K for 4 h. The total amount of PCDDs and DD detected in the liquid nitrogen-cooled trap relative to that of added OCDD was about 17%, i.e., PCDDs and DD which were adsorbed to the fly ash surfaces can evaporate into the gaseous phase. The difference between the evaporation behavior of PCDDs in the present and the previous studies is discussed in the light of their states of existence.
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Affiliation(s)
- Youhei Misaka
- Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
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Rayne S, Sasaki R, Wan P. Photochemical rearrangement of dibenzo[1,4]dioxins proceeds through reactive spirocyclohexadienone and biphenylquinone intermediates. Photochem Photobiol Sci 2005; 4:876-86. [PMID: 16252043 DOI: 10.1039/b505244k] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Photochemical studies on a range of model dibenzo[1,4]dioxins were performed in aqueous and organic solutions. The compounds were found to undergo a photochemically initiated aryl-ether bond homolysis that yields reactive 2-spiro-6'-cyclohexa-2',4'-dien-1'-one and subsequent 2,2'-biphenylquinone intermediates. Under steady-state irradiation, the 2,2'-biphenylquinones were observed to participate in excited state hydrogen abstraction from the organic solvent to give the corresponding 2,2'-dihydroxybiphenyls. In the absence of continued irradiation, 2,2'-biphenylquinones with electron donating substituents thermally rearrange to the corresponding oxepino[2,3-b]benzofurans, whereas the unsubstituted 2,2'-biphenylquinone and its derivatives with electron withdrawing groups thermally rearrange to the corresponding 1-hydroxydibenzofurans.
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Affiliation(s)
- Sierra Rayne
- Department of Chemistry, University of Victoria, P.O. Box 3065, Victoria, British Columbia, CanadaV8W 3V6
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Fueno H, Tanaka K, Sugawa S. Theoretical study of the dechlorination reaction pathways of octachlorodibenzo-p-dioxin. CHEMOSPHERE 2002; 48:771-778. [PMID: 12222770 DOI: 10.1016/s0045-6535(02)00141-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The dechlorination reaction pathways of 1,2,3,4,6,7,8,9-octachlorodibenzo-p-dioxin (OCDD) by the hydrogen atom are investigated by the density-functional theory B3PW91 method. The dechlorination reactions have large exothermicity and small activation energies. The activation energies (approximately 5 kcal/mol) of the sigma-complex formation due to the hydrogen addition are lower than those (approximately 9 kcal/mol) of the direct chlorine abstraction. It is suggested that the sigma-complex plays an important role in the reactions, although it has scarcely been shown in previous studies of the dechlorination of dioxins. The sigma-complex formation is favored at low temperatures and the chlorine abstraction is favored at high temperatures. Furthermore, it is found that the lateral positions have a marginal preference over the longitudinal positions. The dechlorination of OCDD by the hydrogen atom is thus not likely to result in a dominant formation of the laterally substituted toxic congeners.
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Rayne S, Wan P, Ikonomou MG, Konstantinov AD. Photochemical mass balance of 2,3,7,8-TeCDD in aqueous solution under UV light shows formation of chlorinated dihydroxybiphenyls, phenoxyphenols, and dechlorination products. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2002; 36:1995-2002. [PMID: 12026984 DOI: 10.1021/es011311s] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Polychlorinated dibenzo-p-dioxins (PCDDs) are a class of halogenated diaryl compounds that are environmentally important because of their high toxicity and bioaccumulatory properties. There is an incomplete understanding of their photochemistry because the majority of photoproducts, as indicated by incomplete mass balances, have not been identified. We studied the photochemical transformation of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TeCDD) in aqueous solution using 302 nm light. Our results allow for the first photochemical mass balance (92-99%) for this compound and confirm the operation of a novel photochemical pathway, which gives rise to 2,2'-dihydroxy-4,4',5,5'-tetrachlorobiphenyl (4,4',5,5'-TeCDHBP) at >50% conversion from the starting material. Rearrangement from 2,3,7,8-TeCDD to 4,4',5,5'-TeCDHBP takes place following preferential homolytic C-O bond cleavage via a proposed mechanism analogous to the parent dibenzo-p-dioxin system. Photochemical conversion from the starting material to dechlorinated PCDDs or chlorinated phenoxyphenols are minor pathways, although the exact contribution of the strictly dechlorination pathways remains uncertain because of the complexity of the system. The results suggest that the photochemical conversion of PCDDs to chlorinated dihydroxybiphenyls, which are also polychlorinated biphenyl (PCB) metabolites, may be an important part of their environmental fate.
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Affiliation(s)
- Sierra Rayne
- Department of Chemistry, University of Victoria, British Columbia, Canada
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Ivanov IN, Dabestani R, Buchanan AC, Sigman ME. Fluorescence Decay Study of Anisotropic Rotations of Substituted Pyrenes Physisorbed and Chemically Attached to a Fumed Silica Surface. J Phys Chem B 2001. [DOI: 10.1021/jp010858q] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ilia N. Ivanov
- Chemical & Analytical Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, MS-6100, Oak Ridge, Tennessee 37831-6100
| | - Reza Dabestani
- Chemical & Analytical Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, MS-6100, Oak Ridge, Tennessee 37831-6100
| | - A. C. Buchanan
- Chemical & Analytical Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, MS-6100, Oak Ridge, Tennessee 37831-6100
| | - Michael E. Sigman
- Chemical & Analytical Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, MS-6100, Oak Ridge, Tennessee 37831-6100
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Isosaari P, Tuhkanen T, Vartiainen T. Use of olive oil for soil extraction and ultraviolet degradation of polychlorinated dibenzo-p-dioxins and dibenzofurans. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2001; 35:1259-1265. [PMID: 11347942 DOI: 10.1021/es000190d] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
This paper represents a successful laboratory-scale photolysis of soil-bound tetra- to octachlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in olive oil. The irradiation source consisted of two blacklight lamps emitting light at a near-ultraviolet range. Samples used in the experiments included pure 1,2,3,4,6,7,8-heptachlorodibenzofuran, PCDD/F extract made of a wood preservative (chlorophenol product Ky 5), and soil that was highly contaminated with PCDD/Fs. Degradation of 1,2,3,4,6,7,8-heptachlorodibenzofuran dissolved in olive oil proceeded rapidlywith a first-order reaction half-life of 13 min. Irradiation of a soil sample resulted in an 84% reduction in PCDD/F toxicity equivalent (I-TEQ) in 17.5 h. A more complete degradation of soil-bound PCDD/Fs was achieved after extraction of the soil with olive oil. The oil was effective in solubilizing PCDD/Fs. After one extraction at room temperature, only 9% of I-TEQ remained in soil. Irradiation of the resulting extract reduced toxicity of the extract by 99%, and even the highly chlorinated congeners octachlorodibenzo-p-dioxin and octachlorodibenzofuran degraded easily (97 and 99% degradation, respectively). Photodegradation byproducts found included diphenyl ether and small amounts of dechlorination products, which were mainly nontoxic PCDD/Fs. Degradation was probably mediated by light absorption of unsaturated fatty acids and phenolic compounds in olive oil, leading to sensitized photolysis of PCDD/Fs.
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Affiliation(s)
- P Isosaari
- Division of Environmental Health, National Public Health Institute, Kuopio, Finland.
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Konstantinov AD, Johnston AN, Bunce NJ. Successive photocyanation of highly chlorinated aromatic compounds. CAN J CHEM 1999. [DOI: 10.1139/v99-127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Successive photocyanation was found to be a general reaction when chlorinated aromatic compounds were photolyzed with sodium cyanide. The products were polycyanated hydroxychloro compounds with various degrees of chlorine replacement. Although the products from some substrates could be isolated, identified, and characterized, most reactions proceeded with low regioselectivity, which limits their synthetic potential. Quantum yields of substrate disappearance increased with the number of chlorine substituents on a substrate, and followed the expected relationship ϕ-1 is proportional to [CN-]-1. In some cases, ϕ depended also on the concentration of the chloro compound, indicating the involvement of excimers, although the major reaction channel appears to be SN2Ar*. Sensitization and quenching experiments established the triplet excited state to be reactive for all substrates tested.Key words: photocyanation, chlorinated aromatic compounds.
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