- A method for preparing 2, 4, 5 - trichloro phenol (by machine translation)
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The invention discloses a 2, 4, 5 - trichloro phenol industrial preparation method. The 2, 4, 5 - trichloro phenol industrial preparation method, in order to 2, 4 - dichloro nitrobenzene is used as the initial raw materials, by chlorine, reduction and diazo - sandmaier three-step reaction synthesis of 2, 4, 5 - trichloro phenol. The got in the course of 2, 4, 5 - trichloro phenol as yellow solid, purity 97.5%, each step the raw material conversion rate respectively reaches 100%, the whole process of the total yield up to 60%. (by machine translation)
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Paragraph 0010; 0011; 0013; 0014
(2019/02/27)
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- Synthesis of Ti-Al binary oxides and their catalytic application for C-H halogenation of phenols, aldehydes and ketones
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Traditional C–H halogenation of organic compounds often requires corrosive agent or harsh condition, and current researches are focused on the use of noble metals as catalyst. In order to give an efficient, benign, activity-adjustable and cost-effective system for halogenation, a series of Ti-Al mixed oxides are prepared as catalyst through sol-gel in this work. Characterizations reveal all catalysts contain more aluminum than titanium, but preparative conditions affect their composition and crystallinity. Monitoring of particle size, zeta potential and UV–vis of preparative solution reveals that formation of catalyst colloids undergoes chemical reaction, affecting catalyst morphology. In halogenation, all catalysts show moderate to high activities, copper chloride proves to be an effective halogen source rather than sodium chloride. The chlorination and bromination are better than iodization, phenol and ketone appear to be more appropriate substrates than aldehyde. Additionally, oxide backbone of catalyst is more durable than its organic components during recycling. This study may provide new catalytic materials for progress of C–H activation.
- Su, Peigen,Fan, Chao,Yu, Heng,Wang, Wanqin,Jia, Xin,Rao, Qifan,Fu, Chenxi,Zhang, Donghua,Huang, Benhua,Pan, Cheng,Zheng, Aqun,Sun, Yang
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- SYNTHESIS OF CLAY-TEMPLATED SUBNANO-SIZED ZERO VALENT IRON (ZVI) PARTICLES, CLAYS CONTAINING SAME, AND USE OF BOTH IN CONTAMINANT TREATMENTS
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A clay comprising a 2:1 aluminosilicate clay having negative charge sites, the 2:1 aluminosilicate clay containing subnano-sized zero valent iron (ZVI) particles distributed on clay surfaces is provided. In one embodiment, at least some or all of the particles have a cross-section of five (5) angstroms or less. Methods of synthesizing and the novel clays and the clay-templated subnano-scale ZVI particles themselves are also described. Such novel products are useful in a variety of remediation applications, including for reduction and dechlorination reactions.
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Page/Page column 7-8
(2011/06/23)
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- Mechanistic and computational study of a palladacycle-catalyzed decomposition of a series of neutral phosphorothioate triesters in methanol
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The methanolytic cleavage of a series of O,O-dimethyl O-aryl phosphorothioates (1a-g) catalyzed by a C,N-palladacycle, (2-[N,N- dimethylamino(methyl)phenyl]-C1,N)(pyridine) palladium(II) triflate (3), at 25 °C and sspH 11.7 in methanol is reported, along with data for the methanolytic cleavage of 1a-g. The methoxide reaction gives a linear log k2-OMe vs sspKa (phenol leaving group) Bronsted plot having a gradient of βlg = -0.47 ± 0.03, suggesting about 34% cleavage of the P-OAr bond in the transition state. On the other hand, the 3-catalyzed cleavage of 1 gives a Bronsted plot with a downward break at sspKa (phenol) ~ 13, signifying a change in the rate-limiting step in the catalyzed reaction, with the two wings having βlg values of 0.0 ± 0.03 and -1.93 ± 0.06. The rate-limiting step for good substrates with low leaving group sspKa values is proposed to be substrate/pyridine exchange on the palladacycle, while for substrates with poor leaving groups, the rate-limiting step is a chemical one with extensive cleavage of the P-OAr bond. DFT calculations support this process and also identify two intermediates, namely, one where substrate/pyridine interchange has occurred to give the palladacycle coordinated to substrate through the S - P linkage and to methoxide (6) and another where intramolecular methoxide attack has occurred on the P - S unit to give a five-coordinate phosphorane (7) doubly coordinated to Pd via the S- and through a bridging methoxide linked to P and Pd. Attempts to identify the existence of the phosphorane by 31P NMR in a d4-methanol solution containing 10 mM each of 3, trimethyl phosphorothioate (a very slow cleaving substrate), and methoxide proved unsuccessful, instead showing that the phosphorothioate was slowly converted to trimethyl phosphate, with the palladacycle decomposing to Pd0 and free pyridine. These results provide the first reported example where a palladacycle-promoted solvolysis reaction exhibits a break in the Bronsted plot signifying at least one intermediate, while the DFT calculations provide further insight into a more complex mechanism involving two intermediates.
- Liu, C. Tony,Maxwell, Christopher I.,Edwards, David R.,Neverov, Alexei A.,Mosey, Nicholas J.,Brown, R. Stan
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experimental part
p. 16599 - 16609
(2011/02/23)
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- Photocatalytic degradation of lindane by polyoxometalates: Intermediates and mechanistic aspects
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The photocatalytic degradation of lindane (γ-1,2,3,4,5,6-hexachlorocyclohexane) has been studied in the presence of the polyoxometalate PW12O403- in aqueous solutions. Lindane is fully decomposed to CO2, Cl- and H2O, while a great variety of intermediates has been detected using GC-MS, including aromatic compounds (dichlorophenol, trichlorophenols, tetrachlorophenol, hexachlorobenzene, di- and trichloro-benzenodiol), non-aromatic cyclic compounds (penta-, tetrachlorocyclohexene, heptachlorocyclohexane), aliphatic compounds (tetrachloroethane) and condensation products (polychlorinated biphenyls). The number and nature of the intermediates implies that the mechanism of decomposition of lindane is based on both oxidative and reductive processes. Common intermediates have been reported during photolysis of lindane in the presence of titanium dioxide. A similar overall mechanism of polyoxometalates and TiO2 photocatalysis through the formation of common reactive species is suggested.
- Antonaraki,Triantis,Papaconstantinou,Hiskia
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experimental part
p. 119 - 124
(2010/08/22)
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- Leaving group assistance in the La3+-catalyzed cleavage of dimethyl (o-methoxycarbonyl)aryl phosphate triesters in methanol
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The catalytic methanolysis of a series of dimethyl aryl phosphate triesters where the aryl groups contain an o-methoxycarbonyl (o-CO2Me) substituent (4a-i) was studied at 25°C in methanol containing La 3+ at various concentrations and sspH. Determination of the second-order rate constant for La3+ 2-catalyzed cleavage of substrate 4a (dimethyl (o-methoxycarbonyl) phenyl phosphate) as a function of sspH was assessed in terms of a speciation diagram that showed that the process was catalyzed by La3+ 2(-OCH3)x dimers, where x = 1-5, that exhibit only a 5-fold difference in activity between all the species. The second-order catalytic rate constants (k2La) for the catalyzed methanolysis of 4a-i at sspH 8.7 fit a Bronsted relationship of log k2La= (-0.82 ± 0.11)sspKalg + (11.61 ± 1.48), where the gradient is shallower than that determined for a series of dimethyl aryl phosphates that do not contain the o-CO2Me substituent, log k2La = (-1.25 ± 0.06)s spKalg + (16.23 ± 0.75). Two main observations are that (1) the o-CO2Me group preferentially accelerates the cleavage of the phosphate triesters with poor leaving groups relative to those with good leaving groups and (2) it provides an increase in cleavage rate relative to those of comparable substrates that do not have that functional group, e.g., k2La(dimethyl o-(methoxycarbonyl) phenyl phosphate)/k2La(dimethyl phenyl phosphate) = 60. Activation parameters for the La3+2-catalyzed methanolysis of 4a and dimethyl 4-nitrophenyl phosphate show respective ΔH? (ΔS?) values of 3.3 kcal/mol (-47 cal/mol·K) and 0.7 kcal/mol (-46.5 cal/mol·K). The data are analyzed in terms of a concerted reaction where the catalytic complex (La3+2( -OCH3)x-1) binds to the three components of a rather loose transition state composed of a nucleophile CH3O -, a nucleofuge -OAr, and a central (RO)2P 2+-O- in a way that provides leaving group assistance to the departing aryloxy group.
- Edwards, David R.,Liu, C. Tony,Garrett, Graham E.,Neverov, Alexei A.,Brown, R. Stan
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supporting information; experimental part
p. 13738 - 13748
(2010/01/06)
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- Formation of chlorinated phenols, dibenzo-p-dioxins, dibenzofurans, benzenes, benzoquinnones and perchloroethylenes from phenols in oxidative and copper (II) chloride-catalyzed thermal process
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Formation of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and chlorinated phenols on CuCl2 from unsubstituted phenol and three monochlorophenols was studied in a flow reactor over a temperature range of 100-425 °C. Heated nitrogen gas streams containing 8.0% oxygen were used as carrier gas. The 0.00024 mol of unsubstituted phenol and 0.00039 mol of each monochlorophenol were passed through a 1 g and 1 cm SiO2 particle containing 0.5% (Cu by mass) CuCl2. Chlorination preferentially occurred on ortho-(2, 6) and para-(4) positions. Chlorination increased up to 200 °C, and thereafter decreased as temperature increased. Chlorination of phenols plays an important role in the formation of the more chlorinated PCDD/Fs. Chlorinated benzenes are formed possibly from both chlorination of benzene and chlorodehydroxylation of phenols. Chlorinated phenols with ortho chlorine formed PCDD products, and major PCDD products were produced via loss of one chlorine. For PCDF formation, at least one unchlorinated ortho carbon was required.
- Ryu, Jae-Yong
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p. 1100 - 1109
(2008/12/21)
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- A simple DNase model system comprising a dinuclear Zn(II) complex in methanol accelerates the cleavage of a series of methyl aryl phosphate diesters by 1011-1013
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The di-Zn(II) complex of 1,3-bis[N1,N′1-(1,5,9- triazacyclododecyl)]propane with an associated methoxide (3:Zn(II) 2:-OCH3) was prepared and its catalysis of the methanolysis of a series of fourteen methyl aryl phosphate diesters (6) was studied at sspH 9.8 in methanol at 25.0 ± 0.1°C. Plots of kobs vs [3:Zn(II)2: -OCH3]free for all members of 6 show saturation behavior from which KM and kcatmax were determined. The second order rate constants for the catalyzed reactions (k catmax/KM) for each substrate are larger than the corresponding methoxide catalyzed reaction (k2-OMe) by 1.4 × 108 to 3 × 109-fold. The values of kcatmax for all members of 6 are between 4 × 10 11 and 3 × 1013 times larger than the solution reaction at sspH 9.8, with the largest accelerations being given for substrates where the departing aryloxy unit contains ortho-NO 2 or C(=O)OCH3 groups. Based on the linear Bronsted plots of kcatmax vs sspK aof the phenol, βIg values of -0.57 and -0.34 are determined respectively for the catalyzed methanolysis of regular substrates that do not contain the ortho-NO2 or C(=O)OCH3 groups, and those substrates that do. The data are consistent with a two step mechanism for the catalyzed reaction with rate limiting formation of a catalyst-coordinated phosphorane intermediate, followed by fast loss of the aryloxy leaving group. A detailed energetics calculation indicates that the catalyst binds the transition state comprising [CH3O -:6]?, giving a hypothetical [3:Zn(II) 2:CH3O-:6]? complex, by -21.4 to -24.5 kcal/mol, with the strongest binding being for those substrates having the ortho-NO2 or C(=O)OCH3 groups.
- Neverov, Alexei A.,Liu, C. Tony,Bunn, Shannon E.,Edwards, David,White, Christopher J.,Melnychuk, Stephanie A.,Brown, R. Stan
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p. 6639 - 6649
(2008/12/23)
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- Catalysis and inhibition of ester hydrolysis in the presence of resorcinarene hosts functionalized with dimethylamino groups
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Complexation and catalysis of two calixresorcinarene (RES) derivatives with nucleophilic N,N-dimethylamino functions attached to their upper rims in the hydrolysis of carboxylate and sulfonate esters of 4-nitrophenol and 2,4-dinitrophenol have been investigated. Rate constants obey the complexation equation: kobs = kb × Ks + k c[Host]/Ks + [Host] Values of the dissociation constant (Ks) of the complexes are within the range exhibited by other systems such as cyclodextrins-ester complexes. The reactions of sulfonate esters only exhibit inhibition by the macrocyclic hosts. The reactions of the carboxylate esters exhibit catalysis and inhibition depending on the pH of the system. It is proposed that the dimethylamino function in RES3 and RES5 behaves as a nucleophile to form a reactive acylammonium species which subsequently decomposes and regenerates the catalytic amine. In the reaction of substituted phenyl acetates with RES3 the effective charge on the leaving oxygen in the complexed state (+0.88) is slightly more positive than that in the free ester (+0.70). The effective charge on the leaving oxygen in the transition structure is substantially more positive (+0.04 units) than in a model intramolecular reaction of tertiary dimethylamines with aryl esters (-0.53 units). The influence of the host on the reaction in the complex includes an electronic component which is ascribed to solvation of the transition structure of the rate-limiting step by water molecules located within the cavity of the host. It is suggested that this solvation is stronger than that occurring in the transition state for the model intramolecular reaction. Copyright
- Cevasco, Giorgio,Thea, Sergio,Vigo, Daniele,Williams, Andrew,Zaman, Flora
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p. 630 - 636
(2008/02/08)
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- Catalytic polymer-supported potassium thiophenolate in methanol as a method for the removal of ester, amide, and thioacetate protecting groups
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Polymer-supported potassium thiophenolate to remove ester, activated amide, and thioacetate protecting groups catalytically in the presence of methanol is reported.
- MacCoss, Rachel N.,Henry, Dara J.,Brain, Christopher T.,Ley, Steven V.
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p. 675 - 678
(2007/10/03)
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- Electroreduction of Organic Compounds, 34 [1]. Cathodic Dehalogenation of Chloroarenes with Electron-Donating Substituents
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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
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p. 1187 - 1200
(2007/10/03)
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- OH-radical induced oxidation of phenoxyacetic acid and 2,4-dichlorophenoxyacetic acid. Primary radical steps and products
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The reactions of ·OH radicals with 2,4-dichlorophenoxyacetic acid (2,4-D), k = (6.6 ± 0.5) × 109 M-1 s-1, phenoxyacetic acid (PAA), k = (10 ± 1) × 109 M-1 s-1, and 2,4-dichlorophenol (2,4-DCP), k = (7.1 ± 0.5) × 109 M-1 s-1, have been studied using pulse and gamma radiolysis. The ·OH adducts produced by addition to the ring at positions not occupied by substituted groups were oxidized by K3[Fe(CN)6], with the corresponding hydroxylated species analyzed by HPLC. The distribution of ·OH radical addition to the aromatic ring of 2,4-D is C1, 17%; C2/C4, 20%; C3/C5/C6, 47%; and for ·OH reaction with PAA, it is C1, 5.5%; C2/C6, 45%; C3/C5, 11%; C4, 36%. Whereas the hydroxycyclohexadienyl radicals of 2,4-D have no observable reactivity toward oxygen, those of PAA and 2,4-DCP do react, with k(·OH adduct-PAA) + O2 = (5.1 ± 0.2) × 108 M-1 s-1 and k(·OH adduct-2,4-DCP) + O2 = (1.1 ± 0.1) × 108 M-1 s-1. The phenoxyl radicals formed by chloride elimination from the ipso-chloro-·OH adducts of 2,4-D rapidly oxidize TMPD to TMPD·+, k = (3.6 ± 0.5) × 109 M-1 s-1.
- Zona, Robert,Solar, Sonja,Sehested, Knud,Holcman, Jerzy,Mezyk, Stephen P.
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p. 6743 - 6749
(2007/10/03)
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- Novel stabilized activated derivatives of carbamic acid, their process of preparation and their use for the preparation of ureas
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Process for the preparation of stable activated derivatives of carbamic acid, comprising at least one protected amino group and an activated carbamic acid function, from an amino acid derivative in which the amino group is protected. The process includes: a) a step of transformation of the —COOH group of the amino acid derivative into a —CON3 group to obtain an acyl azide; b) a step of transformation of the —CON3 group of the acyl azide into a —NCO group to obtain an isocyanate; c) a step of treating the isocyanate to obtain a stable derivative of carbamic acid.
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- 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
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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
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p. 507 - 518
(2007/10/03)
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- Indium metal as a reducing agent in organic synthesis
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The low first ionisation potential (5.8 eV) of indium coupled with its stability towards air and water, suggest that this metallic element should be a useful reducing agent for organic substrates. The use of indium metal for the reduction of C=N bonds in imines, the heterocyclic ring in benzo-fused nitrogen heterocycles, of oximes, nitro compounds and conjugated alkenes and the removal of 4-nitrobenzyl protecting groups is described. Thus the heterocyclic ring in quinolines, isoquinolines and quinoxalines is selectively reduced using indium metal in aqueous ethanolic ammonium chloride. Treatment of a range of aromatic nitro compounds under similar conditions results in selective reduction of the nitro groups; ester, nitrile, amide and halide substituents are unaffected. Likewise indium in aqueous ethanolic ammonium chloride is an effective method for the deprotection of 4-nitrobenzyl ethers and esters. Indium is also an effective reducing agent under non-aqueous conditions and α-oximino carbonyl compounds can be selectively reduced to the corresponding N-protected amine with indium powder, acetic acid in THF in the presence of acetic anhydride or di-tert-butyl dicarbonate. Conjugated alkenes are also reduced by indium in THF-acetic acid.
- Pitts,Harrison,Moody
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p. 955 - 977
(2007/10/03)
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- Kinetic study of the reactions of chlorine atoms and Cl2.- radical anions in aqueous solutions. II. Toluene, benzoic acid, and chlorobenzene
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The reactions of chlorine atoms and Cl2.- radical ions with toluene, benzoic acid, and chlorobenzene were studied using laser conventional flash photolysis of Na2S2O8 aqueous solutions containing Cl- ions. The reaction rate constants was diffusion-controlled, thus showed no dependence on the σ-Hammett parameter of the substituent in the aromatic ring. The high reactivity of Cl atoms was distinct with that of Cl2.- radical ions, for which the rate constants for the reactions with the substituted benzenes were -/M-sec. The π-complex of benzene yielded very low bond energies (a sequence of chemical reactions unless highly stabilized by the solvent. An electron-transfer reaction pathway was not important for the substrates benzene, toluene, and benzoic acid since phenolic derivatives formed from the disproportionation of HO-CHD radicals were not observed as reaction products. The dissimilarity in the behavior of the Cl-CHD radicals in the gas phase and in organic solvents compared with that in the aqueous phase seemed to be the lack of dissociation of Cl-CHD in aqueous solutions.
- Martire,Bertolotti,Carrillo Le Roux,Braun,Rosso,Bertolotti,Carrillo Le Roux,Braun,Gonzalez
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p. 5385 - 5392
(2007/10/03)
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- Supercritical water oxidation of 2-chlorophenol catalyzed by Cu2+ cations and copper oxide clusters
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Experimentally, the selectivity to decomposition (S/D) (S/D = (amount of 2-chlorophenol (2CP) oxidized to CO2 and H2O)/(disappearance of 2CP)) ratio for oxidation of 2CP with Cu2+ cations in supercritical water was greater than that without any catalysts by 60%. The enhancement was due to a fast precipitation of copper chloride in the supercritical water oxidation (SCWO) process. Formation of toxic byproducts was significantly reduced. Because of a confined environment in the channels of ZSM-5, formation of undesired heavy chlorinated phenols and PAH (polycyclic aromatic hydrocarbon) byproducts in the SCWO of 2CP (catalyzed by CuO/ZSM-5) was also highly suppressed. Only trace light-PAHs with a molecule size less than 6 A were found in the SCWO of 2CP. Carcinogenic PAHs (heavy-PAHs) were not observed. The extended X-ray absorption fine structural (EXAFS) spectra of the catalyst showed that the copper oxides in the channels of ZSM-5 may form Cu3O2 clusters with Cu-Cu and Cu-O bond distances of 2.79 and 1.91 A, respectively. The Cu3O2 clusters were oxidized to Cu3O4 by H2O2 in the supercritical water. Since the diffusion coefficients of copper oxide clusters (Cu3O4) in the channels of ZSM-5 was greater than that of 2CP by at least 3 orders, it is possible that these clusters are relatively mobile in ZSM-5 in the SCWO process. Experimentally, the selectivity to decomposition (S/D) (S/D = (amount of 2-chlorophenol (2CP) oxidized to CO2 and H2O)/(disappearance of 2CP)) ratio for oxidation of 2CP with Cu2+ cations in supercritical water was greater than that without any catalysts by 60%. The enhancement was due to a fast precipitation of copper chloride in the supercritical water oxidation (SCWO) process. Formation of toxic byproducts was significantly reduced. Because of a confined environment in the channels of ZSM-5, formation of undesired heavy chlorinated phenols and PAH (polycyclic aromatic hydrocarbon) byproducts in the SCWO of 2CP (catalyzed by CuO/ZSM-5) was also highly suppressed. Only trace light-PAHs with a molecule size less than 6 angstroms were found in the SCWO of 2CP. Carcinogenic PAHs (heavy-PAHs) were not observed. The extended X-ray absorption fine structural (EXAFS) spectra of the catalyst showed that the copper oxides in the channels of ZSM-5 may form Cu3O2 clusters with Cu-Cu and Cu-O bond distances of 2.79 and 1.91 angstroms, respectively. The Cu3O2 clusters were oxidized to Cu3O4 by H2O2 in the supercritical water. Since the diffusion coefficients of copper oxide clusters (Cu3O4) in the channels of ZSM-5 was greater than that of 2CP by at least 3 orders, it is possible that these clusters are relatively mobile in ZSM-5 in the SCWO process.
- Lin,Wang
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p. 4849 - 4854
(2007/10/03)
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- Cavitation chemistry of polychlorinated biphenyls: Decomposition mechanisms and rates
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Polychlorinated biphenyls (PCBs) are pollutants of environmental concern due to their widespread presence and persistence. The sonolytic destruction of aqueous polychlorinated biphenyls (PCBs) is reported in this article. The kinetics and transformation p
- Zhang, Guangming,Hua, Inez
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p. 1529 - 1534
(2007/10/03)
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- Natural formation of chlorinated phenols, dibenzo-p-dioxins, and dibenzofurans in soil of a Douglas fir forest
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The natural formation of 4-MCP, 24/25- and 26-DCP, and 245-TrCP was detected in four selected areas of a rural Douglas fir forest where the humic layer was spiked in situ with a solution of Na37Cl and covered by an enclosure, after 1 year of incubation. Chlorinated phenols (CP) can be formed naturally from organic matter and inorganic chloride by either de novo synthesis or chloroperoxidase (CPO)-catalyzed chlorination. The natural CP congeners were found to be present in high concentrations in soil compared to the other congeners, except for 245-TrCP which was present in a relatively low concentration. This study did not reveal which source, natural or anthropogenic, caused the observed concentrations. Some 20 chlorinated dibenzo-p-dioxins and dibenzofurans (CDD/F) were found to be formed naturally in soil of the Douglas fir forest; the formation of three 2,3,7,8-substituted congeners, 2378-TeCDD, 12378-PeCDD, and 123789-HxCDD, deserves special attention. A formation mechanism has been proposed which starts from naturally formed CP congeners and which probably involves peroxidase mediation. Chlorination of CDD/F congeners by the CPO-mediated reaction cannot be ruled out, but seems to be less likely due to the absence of several predicted congeners. The natural formation of 4-MCP, 24/25- and 26-DCP, and 245-TrCP was detected in four selected areas of a rural Douglas fir forest where the humic layer was spiked in situ with a solution of Na37Cl and covered by an enclosure, after 1 year of incubation. Chlorinated phenols (CP) can be formed naturally from organic matter and inorganic chloride by either de novo synthesis or chloroperoxidase (CPO)-catalyzed chlorination. The natural CP congeners were found to be present in high concentrations in soil compared to the other congeners, except for 245-TrCP which was present in a relatively low concentration. This study did not reveal which source, natural or anthropogenic, caused the observed concentrations. Some 20 chlorinated dibenzo-p-dioxins and dibenzofurans (CDD/F) were found to be formed naturally in soil of the Douglas fir forest; the formation of three 2,3,7,8-substituted congeners, 2378-TeCDD, 12378-PeCDD, and 123789-HxCDD, deserves special attention. A formation mechanism has been proposed which starts from naturally formed CP congeners and which probably involves peroxidase mediation. Chlorination of CDD/F congeners by the CPO-mediated reaction cannot be ruled out, but seems to be less likely due to the absence of several predicted congeners.
- Hoekstra, Eddo J.,De Weerd, Henk,De Leer, Ed W. B.,Brinkman, Udo A.Th.
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p. 2543 - 2549
(2007/10/03)
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- Rate enhancement by cations in supercritical water oxidation of 2- chlorophenol
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Interactions between cations and Cl species in the supercritical water oxidation (SCWO) of 2.-chlorophenol (2CP) has been investigated in a high- pressure quartz-lined reactor at 673-773 K. Experimentally, we found that the S/D ratio (defined as the amount of 2CP converted to CO2 and H2O/disappearance of 2CP) for SCWO of 2CP was enhanced by cations (such as Li+, Na+, K+, Ca2+, Fe2+, or Fe3+). The S/D ratio increased as the charge density of cations increased (Fe3+> Fe2+ > Li+ > Ca2+ > Na+ > K+). Due to the extremely low solubility of metal salts in the supercritical water, abstraction of Cl in 2CP via an intermediate ((OH)PhCl(δ-)---- M(δ+) was postulated. Formation of these metal chloride (such as KCl, CaCl2, and FeCl3) precipitates in the SCWO of 2CP were identified by X-ray diffraction (XRD) spectroscopy. Since the formation of toxic highly chlorinated phenols and heavy polycyclic aromatic hydrocarbons (PAHs) was notably reduced, abstraction of Cl of 2CP by cations may occur in the early stage of the SCWO process. Interactions between cations and Cl species in the supercritical water oxidation (SCWO) of 2-chlorophenol (2CP) has been investigated in a high-pressure quartz-lined reactor at 673-773 K. Experimentally, we found that the S/D ratio (defined as the amount of 2CP converted to CO2 and H2O/disappearance of 2CP) for SCWO of 2CP was enhanced by cations (such as Li+, Na+, K+, Ca2+, Fe2+, or Fe3+). The S/D ratio increased as the charge density of cations increased (Fe3+>Fe2+>Li+>Ca2+ >Na+>K+). Due to the extremely low solubility of metal salts in the supercritical water, abstraction of Cl in 2CP via an intermediate ((OH)PhClδ-- - - - -Mδ+) was postulated. Formation of these metal chloride (such as KCl, CaCl2, and FeCl3) precipitates in the SCWO of 2CP were identified by X-ray diffraction (XRD) spectroscopy. Since the formation of toxic highly chlorinated phenols and heavy polycyclic aromatic hydrocarbons (PAHs) was notably reduced, abstraction of Cl of 2CP by cations may occur in the early stage of the SCWO process.
- Lin, Kuen-Song,Wang, H. Paul
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p. 3278 - 3280
(2007/10/03)
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- Indium as a reducing agent: Deprotection of 4-nitrobenzyl ethers and esters
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Indium in aqueous ethanolic ammonium chloride is an effective method for the deprotection of 4-nitrobenzyl ethers and esters.
- Moody, Christopher J.,Pitts, Michael R.
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p. 1575 - 1576
(2007/10/03)
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- Effective charge development in the transfer of the acetyl group between nucleophiles in acetonitrile solution: Acetolysis and butylaminolysis of substituted phenyl esters
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Equilibrium and rate constants have been measured for the phenolyses of acetic anhydride in acetonitrile solution. Acetolysis of substituted phenyl acetates by acetate ion possesses a Bronsted βlg value of -1.50 which, together with a βeq value of 2.86, indicates substantial fission of the C-OAr bond in the transition structure. The value of βeq is employed to identify the rate-limiting steps in aminolyses in acetonitrile. Butylaminolysis of substituted phenyl acetates in acetonitrile solution yields amide and substituted phenolate anion and the kinetics obey the general rate law: Rate = k1[ester][amine] + k2[ester][amine]2 + k3[ester][amine][18-crown-6] Free energy plots of log k1 and log k2 exhibit breaks near pKaArOH values of 9 and 8, respectively, and these can be interpreted by a mechanism which involves a common zwitterionic adduct T±, which partitions to give the product by two routes: A involving direct expulsion of the phenolate ion leaving group (k1 parameter) and B involving proton transfer prior to phenolate ion expulsion (k2 parameter). The formation of T± is rate-limiting for the A path and C-OAr bond fission is rate-limiting for the B mechanism.
- Maude, Antony B.,Williams, Andrew
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p. 179 - 183
(2007/10/03)
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- Complexation catalysis: effective charge development in the aminolysis of phenyl esters in chlorobenzene catalysed by crown ethers
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Kinetics of the butylaminolysis of substituted phenyl acetates in chlorobenzene in the presence of a variety of crown ethers obey the following rate law.Rate = kb2 + kc The individual rate constants fit Broensted-type relationships: log kb = -0.75 pKa + 4.21, log kc = -0.58 pKa + 3.41, log kc = -0.61 pKa + 3.18, where pKa refers to the ionization of the phenol in aqueous solution.The Broensted β1g values for kb and kc are calibrated with the value of βeq recently determined for acetyl transfer between phenolate ions in chlorobenzene.The sensitivity, β1g, of kc is consistent with the rate-limiting formation of a crown ether-zwitterion adduct with subsequent fast (non-rate-limiting) ArO-C bond fission.The Broensted data for kb when calibrated by βeq is consistent with rate-limiting proton transfer from zwitterion to base. 18-Crown-6 enables proton transfer to occur between phenol and butylamine in chlorobenzene according to the equation: BuNH2 + ArOH + Crown Bu-NH3+*Crown + ArO-. The equilibrium constant (K) for the above reaction with a series of substituted phenols has a Broensted selectivity (β) of 2.1 compared with that for the ionization of phenols in water.
- Maude, Antony B.,Williams, Andrew
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p. 691 - 696
(2007/10/02)
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- Evidence for a concerted mechanism in the solvolysis of phenyldimethylsilyl ethers
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The trifluoroethoxide-catalyzed trifluoroethanolysis and the hydroxide-catalyzed hydrolysis of a series of phenyldimethylsilyl ethers were examined. A Bronsted plot of the logarithm of the second-order rate constant KTFE for reaction with trifluoroethanol against the pKLG is not linear. The nonlinear plot might be taken as evidence for a change in rate-determining step of a reaction that proceeds through a pentavalent intermediate. However, the Bronsted plot for the hydroxide-catalyzed hydrolysis, where all the leaving groups are of lower pKa than hydroxide, has an identical shape as the Bronsted plot for the trifluoroethanolysis reaction. Therefore, the unusual shape of the Bronsted plots is not due to a change in rate-determining step. It is suggested that the results are most consistent with a one-step concerted mechanism and not with a mechanism involving a pentavalent intermediate.
- Xu, Yiying,Dietze, Paul E.
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p. 10722 - 10727
(2007/10/02)
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- Total synthesis and enzyme-substrate interaction of D-, DL-, and L-Phosphinotricine, 'bialaphos' (SF-1293) and its cyclic analogues
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DL-Phosphonotricine (3) and its cyclic analogue (4) have been synthesized using the four-component isocyanide condensation of Ugi and Ugi-analogous three-component condensation, respectively. High selectivity of the enzyme-substrate interaction was established with the enzymes α-chymotrypsin, phosphodiesterase I, and alkaline mesintericopeptidase, as well as by separation of the racemic mixture to optical antipodes by the α-chymotripsin. The tripeptide 'bialaphos' (11) and its D-antipode (11a) have been synthesized by the method of activated esters, and the cyclic analogue (15) by the DCC method. It was found that the phospholane L-(5) and the tripeptide (18) exhibit anti-tumour activity.
- Natchev, Ivan A.
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p. 125 - 131
(2007/10/02)
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- Charge Description of Base-Catalyzed Alcoholysis of Aryl Phosphodiesters: A Ribonuclease Model
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The release of substituted phenol from aryl uridine-3'-phosphates is catalyzed by bases and involves cyclization to form the 2',3'-cyclic nucleotide.The rate constants for imidazole and hydroxide ion catalysis (kim and kOH, respectively) obey the Broensted equations (25 deg C and 0.25 M ionic strength) log kim = -0.59 pKArOH + 1.40 (n = 7, r = 0.955) and log kOH = -0.54 pKArOH + 6.68 (n = 9, r = 0.967).General-base-catalyzed release of 4-nitrophenol from the 4-nitrophenyl ester (kB) obeys the Broensted relationship log kB = 0.67 pKBH - 7.50 (n = 7, r = 0.989).Charge changes on base and leaving group atoms as determined from the corresponding β and βeq values do not balance.Comparison with data in the literature indicates that the difference in charge may be assigned to the attacking oxygen (2'-hydroxyl) rather than to the phosphoryl oxygens in the O...PO2... group of atoms.Both P-O bond forming and bond fission components of the reaction are considered to be only weakly advanced in a transition state that lies on a concerted pathway.
- Davis, Andrew M.,Hall, Adrian D.,Williams, Andrew
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p. 5105 - 5108
(2007/10/02)
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- THE REACTIONS OF UNACTIVATED ARYL HALIDES WITH SODIUM METHOXIDE IN HMPA; SYNTHESIS OF PHENOLS, ANISOLES, AND METHOXYPHENOLS
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Sodium methoxide reacts with dichlorobenzenes in HMPA to give the chloroanisoles as a result of a SNAr process.Excess MeONa then effects the demethylation of the ethers to give the chlorophenols via an SN2 reaction.With tri- and tetrachlorobenzenes the initially formed chloroanisoles can be dealkylated to chlorophenols or can suffer further substitution to give the chlorodimethoxybenzenes; these react with excess MeONa to give the chloromethoxyphenols.The results obtained with the various isomers of the di-, tri-, and tetrachlorobenzenes are presented and discussed on the basis of the electronic effects of the substituents.
- Testaferri, L.,Tiecco, M.,Tingoli, M.,Chianelli, D.,Montanucci, M.
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p. 193 - 198
(2007/10/02)
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- Preparation of 2,4,5-trichlorophenol and 2,4,5-trichlorophenoxyacetic acid free of 2,3,7,8-tetrachloro-dibenzo-p-dioxin contamination
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A process for the preparation of 2,4,5-trichlorophenol and 2,4,5-trichlorophenoxyacetic acid free of 2,3,7,8-tetrachloro-dibenzo-p-dioxin contamination by the steps of nitrating 1,2,4-trichlorobenzene, reducing the resulting 1,2,4-trichloro-5-nitrobenzene, diazotizing the resulting 2,4,5-trichloroaniline, hydrolyzing the resulting 2,4,5-trichlorobenzenediazonium salt and recovering 2,4,5-trichlorophenol. The 2,4,5-trichlorophenol is reacted with monochloroacetic acid to give 2,4,5-trichlorophenoxyacetic acid. Both the 2,4,5-trichlorophenol and the 2,4,5-trichlorophenoxyacetic acid produced by the process are analytically free of 2,3,7,8-tetrachloro-dibenzo-p-dioxin in analytical tests sensitive to 1 part per billion.
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- Chlorination of phenols and phenoxyacetic acids with sulfuryl chloride
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The process for the chlorination of aromatic compounds of the formula: STR1 wherein R is a member selected from the group consisting of hydrogen, carboxymethyl, and carboxyethyl and Rx is a member selected from the group consisting of hydrogen, 2-methyl, 2,5-dichloro, and 2-chloro, with the proviso that when R is hydrogen, Rx is 2,5-dichloro, consisting of reacting said aromatic compound with sulfuryl chloride in the presence of elemental sulfur or certain sulfur compounds as a catalyst, optionally together with the presence of a Friedel-Crafts acid catalyst and/or an inert organic solvent at temperatures of from 30° C. to 150° C., and recovering a para chlorinated compound.
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- 4-Nitro-2-trichloromethylphenylsulfenamides
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New 4-nitro-2-trichloromethylphenylsulfenamides having a fungicidal and bactericidal action, processes for their manufacture, fungicides containing these compounds as active ingredients, and a process for combating fungi with these compounds.
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- Thiolphosphoric acid-S-4-nitro-2-trichloromethylphenyl esters as fungicides
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New thiolphosphoric acid-S-4-nitro-2-trichloromethylphenyl esters of the formula STR1 where X denotes oxygen or sulfur, and R1 and R2 are identical or different and each denotes a substituted or unsubstituted aliphatic radical of 1 to 18 carbon atoms or a substituted or unsubstituted alicyclic radical of 5 to 18 carbon atoms, processes for their manufacture, fungicides containing these compounds as active ingredients, their manufacture, and processes for combating fungi with these novel compounds.
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- Process for the purification of crude 2,4,5-trichlorophenol
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A novel process for the purification of 2,4,5-trichlorophenol which comprises selectively reacting the major impurities with formaldehyde.
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- Participation of Oligochlorobenzenes in the Base-Catalyzed Halogen Dance
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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.
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p. 4660 - 4666
(2007/10/02)
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- N-(fluorodichloromethylthio)-benzanilides
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New and valuable N-(fluorodichloromethylthio)-benzanilides, a process for their manufacture, fungicides containing these compounds as active ingredients, and a method of combatting fungi with these compounds.
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- Process for producing polyhalogenated phenols
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A process for producing polyhalogenated phenol by mixing a polyhalogenated aniline with an aqueous sulfuric acid solution to obtain a suspension of fine particles of polyhalogenated aniline sulfate having the particle size of 50 μ or less, diazotizing the polyhalogenated aniline sulfate to obtain polyhalogenate benzenediazonium sulfate, hydrolyzing the resulting benzenediazonium sulfate by heating it as such, recycling to the diazotization step the aqueous sulfuric acid solution from which the desired polyhalogenated phenol has been separated.
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