Xn:Harmful;95-95-4Relevant articles and documents
A method for preparing 2, 4, 5 - trichloro phenol (by machine translation)
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Paragraph 0010; 0011; 0013; 0014, (2019/02/27)
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)
Synthesis of Ti-Al binary oxides and their catalytic application for C-H halogenation of phenols, aldehydes and ketones
Su, Peigen,Fan, Chao,Yu, Heng,Wang, Wanqin,Jia, Xin,Rao, Qifan,Fu, Chenxi,Zhang, Donghua,Huang, Benhua,Pan, Cheng,Zheng, Aqun,Sun, Yang
, (2019/06/13)
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.
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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Page/Page column 7-8, (2011/06/23)
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.
Mechanistic and computational study of a palladacycle-catalyzed decomposition of a series of neutral phosphorothioate triesters in methanol
Liu, C. Tony,Maxwell, Christopher I.,Edwards, David R.,Neverov, Alexei A.,Mosey, Nicholas J.,Brown, R. Stan
experimental part, p. 16599 - 16609 (2011/02/23)
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.
Photocatalytic degradation of lindane by polyoxometalates: Intermediates and mechanistic aspects
Antonaraki,Triantis,Papaconstantinou,Hiskia
experimental part, p. 119 - 124 (2010/08/22)
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.
Leaving group assistance in the La3+-catalyzed cleavage of dimethyl (o-methoxycarbonyl)aryl phosphate triesters in methanol
Edwards, David R.,Liu, C. Tony,Garrett, Graham E.,Neverov, Alexei A.,Brown, R. Stan
supporting information; experimental part, p. 13738 - 13748 (2010/01/06)
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.
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
Neverov, Alexei A.,Liu, C. Tony,Bunn, Shannon E.,Edwards, David,White, Christopher J.,Melnychuk, Stephanie A.,Brown, R. Stan
, p. 6639 - 6649 (2008/12/23)
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.
Formation of chlorinated phenols, dibenzo-p-dioxins, dibenzofurans, benzenes, benzoquinnones and perchloroethylenes from phenols in oxidative and copper (II) chloride-catalyzed thermal process
Ryu, Jae-Yong
, p. 1100 - 1109 (2008/12/21)
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.
Catalysis and inhibition of ester hydrolysis in the presence of resorcinarene hosts functionalized with dimethylamino groups
Cevasco, Giorgio,Thea, Sergio,Vigo, Daniele,Williams, Andrew,Zaman, Flora
, p. 630 - 636 (2008/02/08)
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
Catalytic polymer-supported potassium thiophenolate in methanol as a method for the removal of ester, amide, and thioacetate protecting groups
MacCoss, Rachel N.,Henry, Dara J.,Brain, Christopher T.,Ley, Steven V.
, p. 675 - 678 (2007/10/03)
Polymer-supported potassium thiophenolate to remove ester, activated amide, and thioacetate protecting groups catalytically in the presence of methanol is reported.
