- Room-temperature copper-catalyzed oxidation of electron-deficient arenes and heteroarenes using air
-
No pressure: The oxidation of aromatic C-H bonds at room temperature was realized through a copper-catalyzed "oxygenase-type" oxidation of arenes and heteroarenes in the presence of air (see scheme). The reaction involves an oxygen-atom transfer from O2 in the air onto the substrates. Copyright
- Liu, Qiang,Wu, Pan,Yang, Yuhong,Zeng, Ziqi,Liu, Jie,Yi, Hong,Lei, Aiwen
-
supporting information; experimental part
p. 4666 - 4670
(2012/06/30)
-
- Activation of chlorine and fluorine by a phenylazo group towards nucleophilic aromatic substitution. Regioselective preparation of polysubstituted anilines
-
A phenylazo group was used for selective activation of ortho fluorine and chlorine atoms towards nucleophilic aromatic substitution with the propanethiolate anion. This enabled a regioselective synthesis of three substituted 4-alkoxyanilines. The regioselectivity of substitution was confirmed by comparison of experimental NMR chemical shifts with empirically predicted values. The observed reactivity of the substrates is discussed in the context of the substituent effect.
- Fryszkowska, Anna,Tilford, Robert W.,Guo, Fengli,Kaszynski, Piotr
-
p. 2327 - 2333
(2007/10/03)
-
- Formation and destruction of chlorinated pollutants during sewage sludge incineration
-
The limitations facing land filling and recycling and the planned ban on sea disposal of sludge leads to the expectation that the role of sludge incineration will increase in the future. The expected increase in sludge incineration will also increase scrutiny of the main drawback to sewage sludge incineration-the formation of hazardous air pollutants (HAPs). Despite the extensive body of knowledge available on sewage sludge combustion, very few studies have been conducted on the formation of HAPs during sludge combustion. In this work, the interactions between sewage sludge pyrolysis products and sludge ash were investigated using a dual chamber flow reactor system and a horizontal laboratory scale reactor. The results of this study shows that sludge ash can catalyze oxidation and chlorination of organics. In the absence of HCl in the gas stream, sludge ash acts as an oxidizing catalyst, but in the presence of HCl, sludge ash acts as a chlorination catalyst producing high yields of organochloride compounds.
- Fullana, Andres,Conesa, Juan A.,Font, Rafael,Sidhu, Sukh
-
p. 2953 - 2958
(2007/10/03)
-
- Electroreduction of Organic Compounds, 34 [1]. Cathodic Dehalogenation of Chloroarenes with Electron-Donating Substituents
-
The electrochemical reduction of chlorinated arenes with electron-donating substituents, i.e. chlorotoluenes, -anisoles and -phenols, is studied. Preparative electrolyses are run in various solvent-supporting electrolytes under potentiostatic and galvanostatic conditions at lead or carbon cathodes. A partial and mostly regioselective hydrodechlorination of compounds with two or more chloro substituents is possible under suitable conditions. The replacement of one single chloro substituent, in particular in a para-position, is difficult. Highly toxic and persistent oligochloro derivatives are thus transformed into less problematic compounds with a low degree of chlorination. The chlorine content of real-life materials such as extracts of soil contaminated with chlorinated phenols and Nitrofen can also be significantly decreased by electroreduction.
- Kranz, Olaf,Voss, Jürgen
-
p. 1187 - 1200
(2007/10/03)
-
- Removal of dioxins and related aromatic hydrocarbons from flue gas streams by adsorption and catalytic destruction
-
The dioxin removing capacity of the shell dedioxin system (SDDS a - Ti/V oxidative type catalyst) has been tested using the Umefa lab-scale incinerator over the temperature range 100 -230°C and at space velocities of 8000 and 40,000 h-1. Other analogous organic compounds, such as PCBs, PAHs, chlorobenzenes and chlorophenols have also been investigated. Results show a high degree of dioxin removal already at 100°C (82%), which occurs mainly by adsorption. When the temperature is raised a transition towards destruction is seen and at 150°C, gas hour space velocity (GHSV) 8000 and at 230°C, GHSV 40,000 virtually all removal is by destruction. High PCDD/F destruction efficiencies are reported (> 99.9%, based on I-TEQ); the other dioxin-related species and PAHs are also removed and destroyed to a significant extent. The SDDS has proved to be an effective means of destroying organic compounds in the gas phase, particularly dioxins, at temperatures as low as 150°C.
- Liljelind, Per,Unsworth, John,Maaskant, Onno,Marklund, Stellan
-
p. 615 - 623
(2007/10/03)
-
- Identification of surrogate compounds for the emission of PCDD/F (I-TEQ value) and evaluation of their on-line realtime detectability in flue gases of waste incineration plants by REMPI-TOFMS mass spectrometry
-
Correlations between products of incomplete combustion (PIC), e.g., chloroaromatic compounds, can be used to characterise the emissions from combustion processes, like municipal or hazardous waste incineration. A possible application of such relationships may be the on-line real-time monitoring of a characteristic surrogate, e.g., with Resonance-Enhanced Multiphoton Ionization-Time-of-Flight Mass Spectrometry (REMPI-TOFMS). In this paper, we report the relationships of homologues and individual congeners of chlorinated benzenes (PCBz), dibenzo-p-dioxins (PCDD), dibenzofurans (PCDF) and phenols (PCPh) to the International Toxicity Equivalent (I-TEQ) of the PCDD/F (I-TEQ value) in the flue gas and stack gas of a 22 MW hazardous waste incinerator (HWI). As the REMPI detection sensitivity is decreasing with the increase of the degree of chlorination, this study focuses on the lower chlorinated species of the compounds mentioned above. Lower chlorinated species, e.g., chlorobenzene (MCBz), 1,4-dichlorobenzene, 2,4,6-trichlorodibenzofuran or 2,4-dichlorophenol, were identified as I-TEQ surrogates in the flue gas. In contrast to the higher chlorinated phenols, the lower chlorinated phenols (degree of chlorination 4) were not reliable as surrogates in the stack gas. The identified surrogates are evaluated in terms of their detectability by REMPI-TOFMS laser mass spectrometry. The outcome is that MCBz is the best suited surrogate for (indirect) on-line measuring of the I-TEQ value in the flue gas by REMPI-TOFMS. The correlation coefficient r of the MCBz concentration to the I-TEQ in the flue gas was 0.85.
- Blumenstock,Zimmermann,Schramm,Kettrup
-
p. 507 - 518
(2007/10/03)
-
- Dechlorination of pentachlorophenol by zero valent iron and modified zero valent irons
-
The disappearance of pentachlorophenol (PCP) from aqueous solutions in contact with zero valent metals (ZVMs) may be due to dechlorination reactions or sorption to ZVM-related surfaces. Previously reported results on PCP and zero valent iron measured only PCP loss from aqueous solutions and attributed this loss to reaction. In this study, the total amount of unreacted PCP, both that in aqueous solution and that sorbed to ZVM-related surfaces, was measured using a modified extraction method. PCP dechlorination was confirmed by following the appearance of tetrachlorophenol isomers. The results indicate that the rate of dechlorination is much slower than previously reported. In our experiments, electrolytic zero valent iron with a surface area of 0.12 m2/g resulted in an observed first-order rate constant (±95% confidence limits) of 3.9 (±0.7) x 10-3 h-1 or a half-life of approximately 7.4 days. Normalized to surface area, the rate constant (k(SA)) is 3.2 (±0.6) x 10-4 L m-2 h-1. Four amended irons prepared by coating iron with palladium (Pd/Fe), platinum (Pt/Fe), nickel (Ni/Fe), and copper (Cu/Fe) were also used and showed slower removal rates as compared to unamended iron (estimated half-lives of 36-43 days). Slower reaction rates obtained with amended irons as compared to iron have not been previously reported. Overall, this study conclusively demonstrates PCP dechlorination by iron and several bimetallic ZVMs and indicates that it is essential to separate reaction and sorption processes. The disappearance of pentachlorophenol (PCP) from aqueous solutions in contact with zero valent metals (ZVMs) may be due to dechlorination reactions or sorption to ZVM-related surfaces. Previously reported results on PCP and zero valent iron measured only PCP loss from aqueous solutions and attributed this loss to reaction. In this study, the total amount of unreacted PCP, both that in aqueous solution and that sorbed to ZVM-related surfaces, was measured using a modified extraction method. PCP dechlorination was confirmed by following the appearance of tetrachlorophenol isomers. The results indicate that the rate of dechlorination is much slower than previously reported. In our experiments, electrolytic zero valent iron with a surface area of 0.12 m2/g resulted in an observed first-order rate constant (±95% confidence limits) of 3.9 (±0.7) × 10-3 h-1 or a half-life of approximately 7.4 days. Normalized to surface area, the rate constant (kSA) is 3.2 (±0.6) × 10-4 L m-2 h-1. Four amended irons prepared by coating iron with palladium (Pd/Fe), platinum (Pt/Fe), nickel (Ni/Fe), and copper (Cu/Fe) were also used and showed slower removal rates as compared to unamended iron (estimated half-lives of 36-43 days). Slower reaction rates obtained with amended irons as compared to iron have not been previously reported. Overall, this study conclusively demonstrates PCP dechlorination by iron and several bimetallic ZVMs and indicates that it is essential to separate reaction and sorption processes.
- Kim, Young-Hun,Carraway, Elizabeth R.
-
p. 2014 - 2017
(2007/10/03)
-
- PYROLYSIS-GAS CHROMATOGRAPHY-MASS SPECTROMETRY OF POLYCHLOROPHENOLS AND POLYCHLOROPHENATES
-
Pentachlorophenol, 1, its sodium salt and the sodium salts of 2,3,4,5-tetrachlorophenol, 2, and 2,4,6-trichlorophenol, 3, have been submitted to pyrolysis-gas chromatography-mass spectrometry for 20 s at 990 deg C and at 500 deg C.Polychlorophenols (PCPs) and polychlorodibenzodioxins (PCDDs) were formed at the lower temperature.PCPs, PCCDs and polychlorobenzenes (PCBzs) were formed at the higher temperature.Compounds derived from loss of one or two carbon atoms were also formed from the sodium salt of 1 at the higher temperature.A mechanism based on the formation of ketocarbenes and arynes is suggested.
- Bassoli, Angela,Parrilli, Daniele,Rindone, Bruno,Pitea, Demetrio,Siniscalco, Falco
-
p. 333 - 339
(2007/10/02)
-
- REVERSIBLE PROTON TRANSFER IN THE 2,3,5,6-TETRACHLOROPHENOL-N,N-DIMETHYLANILINE HYDROGEN-BONDED COMPLEX STUDIED BY LOW-TEMPERATURE 1H NMR SPECTROSCOPY
-
Low temperature 1H NMR studies of the bridging OHN signal in the hydrogen-bonded complex formed between 2,3,5,6-tetrachlorophenol and N,N-dimethylaniline in C2H5Cl solution have shown that separate signals for the molecular and ion-pair forms of the complex can be observed below -135 deg C (138 K).Analyses of the observed lineshapes have yielded values for the thermodynamic quantities ΔH0, ΔS0 as well as for the activation quantities ΔH, ΔS.
- Ilczyszyn, Marek,Ratajczak, Henryk,Ladd, John A.
-
p. 499 - 504
(2007/10/02)
-
- Photochemistry of halogenated benzene derivatives. Part VI. Photoreactions of tetra- and pentachlorophenols in water-acetonitrile mixtures
-
Laboratory photochemical studies of aqueous acetonitrile solution of some polychlorinated phenols (PCPs) such as 2,3,4,5-tetrachlorophenol (2,3,4,5-Cl4-Pn)(1), 2,3,4,6-Cl4-Pn(2), 2,3,5,6-Cl4-Pn(3), and pentachlorophenol (Cl5-Pn)(4) at λ>285 nm have been carried out for 6 and 24 h exposure times.All the investigated PCPs underwent reductive dechlorination.This process was dependent not only upon the position of OH group but also upon the relative positions of the Cl substituents on the benzene ring.The Cl4-Pn 2 (and 3) and Cl5-Pn (4) also yielded photoproducts of molecular formulae C8H4Cl3NO(M+.=235) and C8H3Cl4NO(M+.=269), respectively.Furthermore, phenol 3 is unique amongst the investigated PCPs; in addition to the above mentioned photoproducts, it yielded hexa-, hepta-, and octachlorodihydroxybiphenyl(s) as well as heptachlorohydroxydiphenyl ether.
- Choudhry, Ghulam Ghaus,Wielen, Frans W. M. van der,Webster, G. R. Barrie,Hutzinger, Otto
-
p. 469 - 475
(2007/10/02)
-
- Participation of Oligochlorobenzenes in the Base-Catalyzed Halogen Dance
-
The three trichlorobenzenes fail to participate in the base-catalyzed halogen dance even on treatment with the favorable base/solvent combination potassium tert-butoxide in hexamethylphosphoric triamide.However, 1,2,3,5- and 1,2,4,5-tetrachlorobenzenes undergo disproportionation to penta- and trichlorobenzenes as well as interconversion into each other.Pentachlorobenzene disproportionates to hexa- and tetrachlorobenzenes, but further reactions of C6Cl6 form pentachlorophenol.Substitution reactions to form aryl tert-butyl ethers are observed as side reactions and are believed to occur by the SNAr mechanism.The phenols produced in several reactions apparently result from E2 cleavage of these ethers.These observations are possibly relevant to the mechanism of formation of 2,3,7,8-tetrachlorodibenzo-p-dioxin from 1,2,4,5-tetrachlorobenzene.
- Mach, Martin H.,Bunnett, Joseph F.
-
p. 4660 - 4666
(2007/10/02)
-
