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1.
M. S. Sultana A. Toyoshima N. Takahashi H. Baba 《Journal of Radioanalytical and Nuclear Chemistry》2001,247(1):193-195
The distribution behavior of astatine was studied at tracer concentrations and over a wide range of carrier iodide concentration in both solvent extraction and back extraction processes. Astatine compounds were extracted instantly into the organic solvent, CS2 from the carrier free and carrier iodide containing solutions. Back extraction of astatine with various NaOH solutions followed by solvent extraction caused the hydrolysis of astatine. The distribution behavior of astatine was explained by the extraction reaction schemes. 相似文献
2.
Methane is shown to react with ethene over silver-exchanged zeolites at around 673 K to form higher hydrocarbons. Methane
conversion of 13.2% is achieved at 673 K over Ag–ZSM−5 catalyst. Under these conditions, H–ZSM−5 does not catalyze the methane
conversion, only ethene being converted into higher hydrocarbons. Zeolites with extra-framework metal cations such as In and
Ga also activate methane in the presence of ethene. Using 13C-labeled methane as a reactant, propene is shown to be a primary product from methane and ethane. 13C atoms were not found in benzene molecules produced, indicating that benzene is entirely originated from ethane. On the other
hand, in toluene, 13C atoms are found in both the methyl group and the aromatic ring. This implies that toluene is formed by the reaction of propene
with butenes formed by the dimerization of ethene, and also by the reaction of benzene with methane. The latter path was confirmed
by direct reaction of 13CH4 with benzene. In this case, 13C atoms are found only in methyl groups of toluene produced. The heterolytic dissociation of methane over Ag+-exchanged zeolites is proposed as a reaction mechanism for the catalytic conversion of methane, leading to the formation
of silver hydride and CH3δ+ species, which reacts with ethene and benzene to form propene and toluene, respectively. The conversion of methane over zeolites
loaded with metal cations other than Ag+ is also described. The reaction of methane with benzene over indium-loaded ZSM−5 afforded toluene and xylenes in yields of
up to 7.6% and 0.9% at 623 K when the reaction was carried out in a flow reactor. 相似文献
3.
The reactions of Nb+ and Ta+ with toluene and picoline and their deuterium-labelled analogues were studied in a Fourier transform ion cyclotron resonance mass spectrometer. Methyl substitution completely changes the reactivities relative to benzene and pyridine. Both metals react to dehydrogenate toluene exclusively. In contrast to benzene, no ring cleavage is observed in the Ta+/toluene reaction. A simple explanation for this difference in reactivities is proposed based on the relative energies of the Hückel orbitals of benzene and toluene. The (b1) symmetric antibonding orbital is higher in energy for toluene. Population of this orbital is necessary for formation of the metallanorbornadiene intermediate and does not occur at thermal energies. Reaction with ring labelled toluene-d5 shows exclusive H2 or D2 elimination in reaction with Nb+ and H2, HD, and D2 elimination in reaction with Ta+. Reactions with the picolines show both dehydrogenation and ring cleavage. Isotope labelling studies show facile H/D scrambling occurs in the intermediate ion-molecule complexes with HCN and DCN both eliminated from the methyl-d3-2-picoline and 4-picoline. The metals react with picoline and pyridine by different mechanisms. The isotope labelling results suggest a metal-hydrido-azepinium structure for the intermediate complex. 相似文献
4.
Shuzi Hayase Yasunobu Onishi Shuichi Suzuki Moriyasu Wada Atushi Kurita 《Journal of polymer science. Part A, Polymer chemistry》1987,25(3):753-763
o-Nitrobenzyl triphenylsilyl ehther/aluminum compound has been previously shown by the authors to act as catalyst in the photopolymerization of epoxides. The dependence of the structure of the silyl ether on the catalyst activity was examined. There were two steps in the photopolymerization. The first step (“Step 1”) is photodecomposition of the silyl ether to silanol. The second step (“Step 2”) is the initiation of polymerization by silanol and the aluminum compound. The introduction of an electron withdrawing group, Cl, CF3, on the benzene ring bonded to Si made the quantum yield of Step 1 low, however, the rate of Step 2 was increased. The low quantum yield of Step 1 was explained in terms of the rate of electron transfer that is controlled by the relative electron density between the CH2 and NO2 in the o-nitrobenzyl group. The acceleration of Step 2 was explained in terms of an increase in silanol acidity that was promoted by the introduction of an electron withdrawing group. The overall rate of the photopolymerizatiol depends to a greater degree on the rate of Step 2 than on that of Step 1. 相似文献
5.
Pd(I) complexes of formula |(η-arene)PdX|2 (X = AlCl4, Al2Cl7; arene = benzene, toluene, p-xylene) are active catalysts for the ethylene dimerization under mild conditions; a mechanism for the reaction is suggested. 相似文献
6.
Baba T Abe Y Nomoto K Inazu K Echizen T Ishikawa A Murai K 《The journal of physical chemistry. B》2005,109(9):4263-4268
Methane is shown to react with ethene over In-loaded ZSM-5 to higher hydrocarbons such as propene and toluene at around 673 K. Such methane conversion is not catalyzed by proton-exchanged ZSM-5 (H-ZSM-5) under the same conditions, only C2H4 being converted to higher hydrocarbons. By using 13C-labeled methane (13CH4) as a reactant, the reaction paths for the formation of propene, benzene and toluene were examined. 13C-labeled propene (13CC2H6) is formed by the reaction of 13CH4 with C2H4. The lack of 13C-labeled benzene revealed that propene is not transformed to benzene, which instead originates entirely from C2H4. The 13C atom is inserted both into the methyl group and benzene ring in the toluene formed. This indicates that toluene is formed by two reaction paths; the reaction of 13CC2H6 with butenes formed by the dimerization of C2H4 and the reaction of benzene with 13CH4. The existence of the latter path was proved by the direct reaction of 13CH4 with benzene. The reaction of methane with benzene was also carried out in a continuous flow system over In-loaded ZSM-5. The reaction afforded 7.6% and 0.9% yields of toluene and xylenes, respectively, at 623 K. 相似文献
7.
M.S. Sultana A. Toyoshima A. Mito N. Takahashi H. Baba H. Watarai 《Journal of Radioanalytical and Nuclear Chemistry》2000,243(3):631-634
The solvent extraction behavior of radioioine and astatine has been investigated under various conditions in order to compare the extraction behavior of astatine with radioiodine at tracer concentration. In this study, basic tracer solutions of astatine and radioiodine were extracted into the CS2 solution under various conditions. Astatine existed as a pure species in the tracer solution and formed cationic compound in the acidic solution which was also extracted into the organic solvent instantaneously. On the other hand, radioiodine existed as a complex in the tracer solution and was partly extracted into the organic solvent at tracer concentration. The observed different extraction behavior of astatine and radioiodine were consistently explained by the respective proposed extraction reaction schemes. 相似文献
8.
The secondary reaction of toluene is difficult to be suppressed in benzene alkylation with methanol over conventional acidic zeolite catalysts. Moreover, the formation of coke yet remains a challenging problem. In this study, Na-Y zeolites were modified with ammonium carbonate (AC), citric acid (CA) and caesium nitrate(CN) to evaluate the alkylation of benzene with methanol, which was also characterized by XRD, SEM, FT-IR, N2 adsorption and Py-IR. For the Na-Y treated with AC-CA-CN, not only the catalytic selectivity for the alkylation of benzene with methanol was improved (the total selectivity of toluene and xylene was 97.9% and toluene selectivity was 86.4%), but also the quantity of coke was greatly decreased. 相似文献
9.
The chemical effects induced by the track structure of heavy ions have been exploited to show that H2 production in the radiolysis of simple aromatic liquids (benzene, pyridine, toluene and aniline) is primarily due to second order processes. Similar dependences of H2 yields on the linear energy transfer, LET, for each of these compounds suggest a common mechanism for H2 formation. Furthermore, the yields of H2 are significant at very high LET and they approach that found with aliphatic compounds. Yields of “dimers” (biphenyl, bibenzyl, dipyridyl, and diphenylamine for benzene, toluene, pyridine, and aniline, respectively) have different dependences on LET reflecting the variety of pathways leading to their production. Bibenzyl formation in toluene exhibits a complex dependence on LET suggesting several competing pathways for its production whereas biphenyl formation in benzene is nearly independent of LET suggesting a unimolecular process. Dipyridyl, and diphenylamine yields in pyridine and aniline, respectively, decrease with increasing LET, which indicates that their precursor is being depleted. 相似文献
10.
V. I. Potkin S. K. Petkevich R. V. Kaberdin P. V. Kurman 《Russian Journal of Organic Chemistry》2007,43(11):1617-1621
Bromination of 3,4,4-trichlorobut-3-enoic acid in boiling carbon tetrachloride led to the formation of 2-bromo-3,4,4-trichlorobut-3-enoic acid as a result of replacement of hydrogen in the CH2 group. The reaction at 40°C involved the double C=C bond to give 3,4-dibromo-3,4,4-trichlorobutanoic acid. The brominated acids were converted into the corresponding chlorides which were used to acylate benzene, toluene, and bromobenzene according to Friedel-Crafts. The acylation was not selective, and only the reaction of 3,4-dibromo-3,4,4-trichlorobutanoyl chloride with benzene gave 3,4-dibromo-3,4,4-trichloro-1-phenylbutan-1-one as the only product. 1-Aryl-2-bromo-3,4,4-trichlorobut-3-en-1-ones were synthesized by bromination of the corresponding 1-aryl-3,4,4-trichlorobut-3-en-1-ones which were prepared previously by Friedel-Crafts acylation of substituted benzenes with 3,4,4-trichlorobut-3-enoyl chloride. 相似文献
11.
Benzenediazonium tetrafluoroborate in 2,2,2-trifluoroethanol decomposes to give fluorobenzene and phenyl 2,2,2-trifluoroethyl ether. In the presence of benzene, toluene, trifluoromethyl-benzene or anisole, the respective biphenyl derivatives are formed in addition to fluorobenzene and the ether. The distribution of the isomeric substituted biphenyls is consistent with an electrophilic substitution. No homolytic products (diazo tars, benzene) are formed. The reaction kinetics clearly show that ether formation and aryl-dediazoniations are of second-order type, i.e. that trifluoroethanol and the benzene derivatives mentioned above are rate-determining factors. It is shown that these results exclude the SN1-mechanism which is usually assumed for heterolytic dediazoniations; free aryl cations are therefore not involved in these reactions. An SN2-like mechanism seems to be the most likely, but one involving an encounter complex containing the dissociated benzenediazonium ion is also consistent with the experimental data. 相似文献
12.
Theo Maulbetsch Dr. Eva Jürgens Prof. Dr. Doris Kunz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(46):10634-10640
The use of carbon monoxide as a direct reducing agent for the deoxygenation of terminal and internal epoxides to the respective olefins is presented. This reaction is homogeneously catalyzed by a carbonyl pincer-iridium(I) complex in combination with a Lewis acid co-catalyst to achieve a pre-activation of the epoxide substrate, as well as the elimination of CO2 from a γ-2-iridabutyrolactone intermediate. Especially terminal alkyl epoxides react smoothly and without significant isomerization to the internal olefins under CO atmosphere in benzene or toluene at 80–120 °C. Detailed investigations reveal a substrate-dependent change in the mechanism for the epoxide C−O bond activation between an oxidative addition under retention of the configuration and an SN2 reaction that leads to an inversion of the configuration. 相似文献
13.
Pd(II) complexes and twelfth-series heteropoly acids (HPA) H9[PMo6V6O40] and H3[PMo12O40] supported on silica gel oxidize benzene and toluene at 95°C. The formation of methyldiphenylmethane in the oxidation of
toluene on HPA/SiO2 and (PdCl2−HPA)/SiO2 catalysts, KIE>1 for the toluene/toluene-d8 pair, and greater rate for toluene than for benzene are in accord with a one-electron transfer mechanism.
L. M. Litvinenko Institute of Physical Organic and Coal Chemistry, National Academy of Sciences of Ukraine, 70 R. Lyuksemburg
ul., Donetsk 340114, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 4, pp. 249–252, July–August,
1999. 相似文献
14.
Serigne Sarr Julien Pilm Gilles Montavon Jean-Yves Le Questel Nicolas Galland 《Molecules (Basel, Switzerland)》2021,26(15)
The nature of halogen-bond interactions was scrutinized from the perspective of astatine, potentially the strongest halogen-bond donor atom. In addition to its remarkable electronic properties (e.g., its higher aromaticity compared to benzene), C6At6 can be involved as a halogen-bond donor and acceptor. Two-component relativistic calculations and quantum chemical topology analyses were performed on C6At6 and its complexes as well as on their iodinated analogues for comparative purposes. The relativistic spin–orbit interaction was used as a tool to disclose the bonding patterns and the mechanisms that contribute to halogen-bond interactions. Despite the stronger polarizability of astatine, halogen bonds formed by C6At6 can be comparable or weaker than those of C6I6. This unexpected finding comes from the charge-shift bonding character of the C–At bonds. Because charge-shift bonding is connected to the Pauli repulsion between the bonding σ electrons and the σ lone-pair of astatine, it weakens the astatine electrophilicity at its σ-hole (reducing the charge transfer contribution to halogen bonding). These two antinomic characters, charge-shift bonding and halogen bonding, can result in weaker At-mediated interactions than their iodinated counterparts. 相似文献
15.
Magda F. Fathalla 《中国化学》2012,30(1):109-114
Kinetics of the reaction of 2‐chloro‐3,5‐dinitrobenzotriflouride with aniline were studied in toluene, methanol‐toluene binary solvents, benzene and chloroform. The reaction in toluene exhibits third‐order kinetics consistent with aggregates of aniline. Thermodynamic parameters (H#, (S# and (G#are calculated and discussed for the reaction of 2‐chloro‐3,5‐dinitrobenzotriflouride with aniline in methanol‐toluene. Molecular complexes between aniline and the substrate are rejected spectrophotometricaly. The mechanism is studied and compared with the reaction in presence of pyridine. It shows an amine dependence and formation of homo and/or hetero mixed aggregates between aniline and pyridine i.e. dimer mechanism. 相似文献
16.
A. von Zelewsky 《Helvetica chimica acta》1972,55(8):2941-2947
The diamagnetic crystalline Jodo-Co(II)-cobyrinicacid-heptamethylester dissolves in benzene or toluene forming solutions which contain the monomeric paramagnetic complex unit. From anisotropic ESR.-parameters, measured in frozen solutions, follows a ground state configuration (dxz,dyz)4(dxy)2(dz2)1 for the Co(II). The unpaired electron is highly delocalized to the axially coordinated iodide ion, giving rise to a strong hyperfine coupling with the iodine nucleus. The complex forms in a very fast and completely reversible reaction a 1:1 adduct with molecular oxygen in toluene solutions below ca. 280° K. ESR.-parameters of the oxygen adduct are presented and discussed. Thermodynamic data for the formation reaction of the adduct are estimated. 相似文献
17.
Paul W. Schmalzl Roger A. Upham Larry L. Miller 《Plasma Chemistry and Plasma Processing》1982,2(1):43-59
A series of aromatic compounds C6H5X (X=CH3, Cl, NO2, NH2, OCH3, CO2CH2CH3, COCH3, CN) were reacted with hydrogen in a 13.6-MHz inductively coupled glow discharge. The flow rates of aromatic and hydrogen were typically 0.5 mmol/min and 18 mmol/min, respectively. The applied power was varied from 50–200 W and the total pressure was varied from 2–14 torr. The products were collected and analyzed by gas chromatography. Three types of reactions were observed: (1) addition of hydrogen to the aromatic, (2) replacement of the group X by hydrogen, and (3) reactions characteristic of aromatic in the absence of hydrogen. The toluene reaction was studied most carefully. Methylcyclohexenes and benzene were the major products identified. The benzene was optimized by increasing the power and decreasing the pressure of either hydrogen or toluene. Reaction of toluene-d8 with hydrogen revealed that hydrogens were sequentially exchanged for deuteria on toluene and each of the products. A new apparatus is described which allows flow rates and pressure to be preselected and controlled and which allows a series of product samples to be collected without quenching the plasma. 相似文献
18.
Takaya Matsumoto 《Catalysis Surveys from Asia》2007,11(1-2):31-48
In this article, two kinds of our transition metal-catalyzed olefin arylations are summarized and discussed. The first one
is Ir-catalyzed novel anti-Markovnikov hydroarylation of olefins with benzene. Using this reaction catalyzed by [Ir(μ-acac-O,O′,C3)(acac-O,O′)(acac-C3)]2 (acac = acetylacetonato), 1, straight-chain alkylarenes, which were not obtainable by the conventional Friedel-Crafts aromatic alkylation with olefins,
were able to be successfully synthesized directly from arenes and olefins with the higher selectivity than that of branched
alkylarenes. This is the first efficient catalyst which shows the desirable high regioselectivity. The reaction of benzene
with propylene gave n-propylbenzene and cumene in 61% and 39% selectivities, respectively, and the reaction of benzene and styrene afforded 1,2-diphenylethane
in 98% selectivity. The reaction of alkylarene and olefin showed meta and para orientations. A wide range of olefins and arenes
can be employed for the synthesis of alkylarenes. The mechanism of the reaction involves C–H bond activation of benzene by
Ir center to form Ir–phenyl species. The second reaction is Rh-catalyzed oxidative arylation of ethylene with benzene to directly
produce styrene, namely one-step synthesis of styrene. The reaction of benzene with ethylene catalyzed by Rh(ppy)2(OAc) (ppyH = 2-phenylpyridine, OAc = acetate), 3 with Cu oxidizing agent gave styrene and vinyl acetate in 77% and 23% selectivities, respectively, in contrast to those by
Pd(OAc)2, 47% of styrene and 53% of vinyl acetate. The mechanism of the reaction involves Rh-mediated C–H bond activation of benzene,
which appears to be a rate-determining step. Furthermore, Rh complexes in a Rh(I) oxidation state at the beginning of the
reaction work as catalysts for the reaction by addition of acacH and O2 without any oxidizing agent, like Cu salt. 相似文献
19.
Henrieta Nichipor Elena Dashouk Svetlana Yacko Yongxia Sun Andrzej G. Chmielewski Zbigniew Zimek Sylwester BuŁka 《Radiation Physics and Chemistry》2012,81(5):572-579
Computer simulations of benzene and toluene decomposition in air (79% N2+21% O2) and in flue gas (87% N2+10% O2+3% H2O+160 ppm SO2+80 ppm NO) under electron beam (EB) irradiation were carried out using computer code KINETIC and GEAR method. 285 reactions involving 73 species and 294 reactions involving 78 species were considered for simulation of benzene and toluene decomposition, respectively. Calculation results of benzene and toluene decomposition in air under electron beam agree well with the published experimental results. OH radicals play a main role in benzene or toluene decomposition. 相似文献
20.
Peng Dong Zeyu Li Dong Ji Xiaorui Wang Hongfei Yun Zhisong Du Jie Bian Guixian Li 《Journal of inclusion phenomena and macrocyclic chemistry》2018,90(1-2):149-155
Modified Y type catalyst (M-Y) shows great potential for the preparation of toluene attribute to catalyst topology and synergistic effect of Lewis acid and Brönsted acid in the alkylation reaction. However, it still remains a big challenge to build a reaction mechanism. Thereby, based on the study of HZSM-5, H-beta and M-Y catalysts structure and physical properties, a plausible reaction mechanism was proposed. The samples were characterized by X-ray diffraction, N2 adsorption/desorption, Fourier transform infrared absorption spectra and Pyridine adsorption infrared. The activity of catalysts was tested in benzene alkylation with methanol and was found to be in the following increasing order: Na-Y (no effect)?<?H-Y?<<?HZSM-5?<?H-beta?<?M-Y. 相似文献