Mechanism of negative ion formation from phenol and para-chlorophenol by interaction with free electrons

Dissociative electron attachment (DEA) to phenol and para-chlorophenol in the energy range 0-12 eV is studied. Analogies in formation of the resonance states in an ionic benzene and its derivatives are found to arise from the similarity of the aromatic base of the molecules. Differences in DEA processes are defined mainly by the influence of the functional OH-group and, to a lesser degree, by the presence of a chlorine atom. A correlation between the energies of the resonance states and ionization energies of p-chlorophenol and phenol, analogous to that found previously for phenol, is proved. On this basis it is established that the dominating mechanism for formation of molecular negative ions at energies above 5 eV is Feshbach resonance.Copyright 2000 John Wiley & Sons, Ltd.     

镍-钒催化剂作用下由苯直接氧化氨化合成苯胺

设计并制备了Ni-V/γ-Al2O3催化剂, 研究了其上苯用过氧化氢氧化氨化一步直接合成苯胺的性能和不同氨基源对合成苯胺的影响. 实验结果显示：在本文条件下, Ni/γ-Al2O3和V/γ-Al2O3催化剂均能活化苯环上C—H键, 使苯一步氧化羟基化为苯酚. Ni、V双组分催化剂则表现出较好的合成苯胺活性和选择性, 催化剂中Ni/V摩尔比在5.5时催化活性和选择性最好,目标产物苯胺的选择性达到85％, 远远高于主要副产物苯酚的选择性. 反应时间宜控制在2 h左右, 反应最佳温度为333 K. 尿素在碱性条件下可作为氨基化试剂, 在Ni-V/γ-Al2O3催化剂作用下使苯直接氧化氨化为苯胺, 尿素和氨水作为共氨化剂表现出对生成苯胺有利的协同效应.     

Thermodynamic properties of the benzene-phenol dimer in dilute aqueous solution

Precise vapor pressure-solubility measurements have been obtained for dilute solutions of benzene and phenol in water at 15, 25, 35 and 45°C. All of the results are consistent with a mass action model that attributes deviations from ideal solution behavior to the formation of benzene dimers and hetero-dimers between benzene and phenol. The benzene-phenol dimer forms endothermically at 25°C, with a very large negative heat capacity, and a formation constant that reaches a maximum value of 0.66 l-mol^?1 at approximately 35°C. Thermodynamic properties of the benzene-phenol dimer are reported and compared with those of other aggregates that are believed to be stabilized primarily by hydrophobic interactions.     

Ni-Zr-Ce／Al2O3催化剂上H2O2作氧化剂直接使苯氧化胺化一步合成苯胺研究

设计制备了Ni-Zr-Ce/Al_2O_3催化剂,研究了其上用H_2O_2直接将苯氧化胺化 合成苯胺的活性。发现在常压、50 ℃的温和条件下,该催化剂对苯、氨水与 H_2O_2直接氧化胺化生成苯胺有较好活性,并且其对苯胺的选择性远远大于对苯酚 的选择性。提高反应原料中氨水对苯的比例,能提高苯胺的收率,且不会增加苯酚 的生成量。本方法能耗低,原子利用率高,为苯胺的绿色合成提供了一条新的路径 。     

Electron impact studies on oximes: Mass spectra of the condensation products of aniline,phenol and thiophenol with benzhydroximoyl chloride

The condensation products derived from aniline, phenol and thiophenol by treatment with benzhydroximoyl chloride, exhibited a stepwise (in the first two cases) or concerted (in the third case) loss of OH. and C6H5N from the corresponding skeletally rearranged molecular ions, affording [C6H5C?X]⁺ ions (where X = NH or o or S) when subjected to electron impact. The process has been substantiated by deuterium labelling and exact mass measurements. The base peaks in all the spectra were due to the aniline, phenol and thiphenol radical ions as the case may be, obtained by a shift prior to fragmentation of the oxime hydrogen to the heteroatom contained in these ions.     

苯酚和苯胺类衍生物的结构与薄层色谱保留值关系的研究

以不同比例的己烷－乙酸乙酯二元体系作为展开剂,在硅胶板上测定了２４种苯酚和苯胺类衍生物的比移值Ｒｆ。用斜交因子分析方法将这２４种化合物分为具有不同特征的两大类：第一类的苯环上均不含甲基,而第二类的苯环上均含甲基。第一类化合物的比移值均比第二类要小;苯环上取代基团使Ｒｆ值增大的顺序为ＣＨ３＞ＯＨ＞ＮＨ２;邻位取代的化合物,由于分子内形成氢键,极性减弱,因而比移值增大。分别对两类化合物的保留值与其拓扑指数进行多元回归分析的结果表明,它们的色谱保留行为与其分子结构之间存在着较好的相关性。     

苯酚和苯胺在超高交联吸附树脂上的共吸附行为

研究了水溶液中苯酚和苯胺在超高交联吸附树脂NDA103、NDA101、NDA100上的竞争吸附和协同吸附行为.实验结果表明,单组分苯酚或苯胺水溶液和双组分共存水溶液中吸附质分子在超高交联吸附树脂上的吸附等温线均符合Langmuir模型.当双组分摩尔比为1∶1时,在较低平衡浓度范围内苯酚和苯胺在树脂上呈现竞争吸附行为,其主导机制是两种吸附质分子对树脂内外表面上π-π作用吸附位点的直接竞争;而在较高平衡浓度范围内呈现协同吸附行为,其主导机制是两种吸附质分子之间的氢键作用.吸附温度由293K升至313K时,苯酚和苯胺在NDA103上的协同吸附作用加强,而在NDA101和NDA100上的协同吸附作用变化不明显.     

Track effects in the radiolysis of aromatic liquids

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.     

Craquage thermique de l'aniline 1-14C

Thermal cracking of aniline 1-¹⁴C at atmospheric pressure at 900°C and a contact time of 2.5 sec breakdown mechanisms of the formation of benzene with an elimination of nitrogen, and formation of heterocyclic compounds and condensation products has been studied. Most of the degradation compounds are produced by a mechanism similar to the primary mechanism for the degradation of phenol: elimination of HCN with formation of inactive C₅H₆. The formation of nitriles is not negligible.     

Nucleophilic substitution in the side chain of 5-membered heterocycles—I : Reactions of furfuryl, 2-thenyl and benzyl chlorides with aniline in acetonitrile and in benzene

The reaction kinetics of furfuryl, 2-thenyl and benzyl chlorides with aniline has been studied in acetonitrile and benzene solutions, The reactions are third order overall, first order with respect to the chloromethyl compound and second order with respect to aniline. In benzene solutions the kinetics at high aniline concentrations (≥0·8 M) deviate from the third order equation. The remarkable increase in k₃, not depending on the polarity of the reaction medium, is ascribed to the association of aniline in benzene. The reactions in acetonitrile are faster than in benzene; in both solvents furfuryl chloride reacts faster than 2-thenyl and benzyl chlorides, the latter being the less reactive. The large negative activation entropies, consistent with an ordered and highly polar transition state, determine the observed rate sequence. The rate constants were correlated with the polar constants for heterocycles.     

The influence of substituent groups on the resonance stabilization of benzene. An ab initio computational study

Accurate G3(MP2) calculations of the enthalpies of formation (Delta(f)H298) of organic molecules permit replication and extension of calculations that were formerly dependent on experimental thermochemical results. A case in point is Kistiakowski's classical calculation of the total stabilization enthalpy of benzene relative to that of cyclohexene, called for many years the "resonance energy". This paper investigates extension of the classical calculation to substituted benzenes. Slight modification of the usual procedure for Delta(f)H298 determination permits exclusion of all empirical information, leaving a purely ab initio result. Stabilization enthalpies relative to the corresponding 4-substituted cyclohexenes are presented for benzene, toluene, aniline, phenol, phenylacetylene, styrene, ethylbenzene, and phenylhydrazine. In the process of calculating these stabilization enthalpies, we have also obtained 42 values of Delta(f)H298 for monosubstituted benzenes, cyclohexenes, and cyclohexanes, 24 of which are not in the standard reference literature. For the remaining 18 G3(MP2) results, the unsigned mean difference between calculated Delta(f)H298 values and experimental results is +/-0.91 kcal x mol(-1).     

NEW FLUOROSILOXANE AS A COATING MATERIAL FOR NERVE AGENT SENSORS

Polymer coated quartz crystal microbalance （QCM） sensor based on the frequency shifts due to the adsorption of compounds at the surface of modified quartz crystal electrode is an effective method for detection of sarin （GB） which is a highly toxic nerve warfare agent. A new fluorosiloxane polymer has been synthesized through 6 steps from trifluoromethyl benzene. The synthesis was achieved from trifluoromethyl benzene through nitration, hydrogenation. The obtained m-nitrotrifluoromethyl aniline was treated with NANO2, and then hydrolyzed to m-nitrotrifluoromethyl phenol, m-nitrotrifluoromethyl phenol was reacted with allyl bromide to the ether product. The product was rearranged by Claisen rearrangement, and then reacted with polymethylhydrosiloxane under catalyst of Pt/DVTMS. The fluorosiloxane polymer can be obtained. The polymer has been successfully used as QCM coating material     

Resonance enhanced laser ionisation mass spectrometry of four aromatic molecules

Multiphoton ionisation and fragmentation of aniline, benzene, N,N-dimethyl and 2,4-dimethyl aniline has been studied by laser ionisation mass spectrometry under collision free conditions. All four molecules undergo efficient resonance-enhanced two-photon ionisation (R2PI) with relatively low laser intensities at λ = 266 nm producing the parent ion almost exclusively. At higher intensities, high order processes compete producing extensive fragmentation. At 266 nm, all the major fragment ions are produced by R3PI. For aniline excited at 294 nm, energetic considerations suggest R4P1 formation of fragments with differences in fragmentation between 266 and 294 nm reflecting the differing orders and energies above threshold of the competing processes. Comparison of R2P1 efficiencies in aniline and benzene shows that the cross sections for ionisation of the resonant intermediate ₁B² excited state in both molecules are approximately equal and independent of wavelength in the range 250–300 nm.     

Catalytic activity of iron-containing polymers in hydroxylation of benzene with hydrogen peroxide

Hydroxylation of benzene with hydrogen peroxide in aqueous acetonitrile at 50°C was studied. The KU-2-8 and KU-1 cation exchangers, and also specially synthesized cation exchangers and phenolformaldehyde resins derived from pyrocatechol and resorcinol, all modified with Fe(III) cations, were used as catalysts. The macrocomplex KU-2-8/Fe³⁺ showed the highest catalytic activity and ensured 32% yield of phenol in 15 min. The formation of phenol depends in a complex fashion on the initial concentration of hydrogen peroxide, content of Fe(III) ions in the polymer, and reaction time.     

Ejection of Cluster Ions from a Liquid Beam of an Aniline-Propanol Solution Following Laser Photoionization

A simple technique of preparing a continuous laminar liquid flow in vacuum (liquid beam) was developed and combined with multiphoton ionization and a time-of-flight mass spectrometer. This technique was applied to the study on resonance photoionization of an aniline (AN)-propanol (PrOH) solution (0.1 – 0.3 M). Binary cluster ions of aniline and propanol, AN⁺(PrOH)_n (n ≤ 1), and protonated propanol cluster ions, H⁺(PrOH)_n (n ≤ 1), were observed as product ions in the gas phase. The relative intensities of AN⁺PrOH and those of H⁺(PrOH)₂ were measured as functions of the excitation laser power and the concentration of aniline in the propanol solution. The dependences of the ion intensities on the laser power and the AN concentration are explained in terms of a Coulomb ejection model, where the ions are ejected from the surface by Coulomb repulsion exerted from neighboring ions. It is also concluded that H⁺(PrOH)_n is produced by a proton transfer reaction from an aniline ion to solvent molecules in the solution.     

Radiochemical Study of Reactions of Diethylsilylium Ions with Dibutyl Ether in the Gas and Liquid Phases

Reactions of diethylsilylium ions with dibutyl ether in the gas and liquid phases were studied radiochemically. These reactions, as those with benzene and alcohols, are accompanied by partial rearrangement of diethylsilylium ions into monoethylsilylium and dimethylsilylium ions. The extent of transformations of the (C₂H₅)₂SiT⁺ ions decreases in going from benzene to dibutyl ether, which is due to the higher energy of adduct formation with the ether, compared to benzene.     

Resonance electron-capture mass spectra of azobenezene and its monosubstituted derivatives

The negative-ion mass spectra of azobenezene and its derivatives were obtained using the resonance electron-capture technique. The molecular negative ion peaks (M^?·) were found to be dominant for almost all of these compounds. Different mechanisms of formation of molecular ions in two energy regions are proposed and the pathways of fragmentation are discussed. It is shown that fragment ions are formed predominantly by direct bond breaking except for those which derive from long-lived resonance states of M^?·.     

The presumptive detection of benzene in water in the presence of phenol with an active membrane-UV photo-ionisation differential mobility spectrometer

Studies with a new technique, active membrane-differential mobility spectrometry, with aqueous standards of benzene and phenol are described. The atmospheric pressure photo-ionisation chemistries of benzene and phenol in the presence of oxygen are similar in that benzene forms phenol radicals that subsequently react to yield diphenylether and 4-phenoxyphenol products. Further phenol sequesters charge from benzene ions leading to a significant loss of sensitivity. This is an important consideration in the development of screening techniques for the presence of benzene in environmental water samples. This challenge was addressed by including a pre-separation stage prior to photo-ionisation, and a 10 cm long polydimethylsiloxane active membrane inlet using nitrogen as a carrier gas was used to sample, concentrate and deliver low resolution separations to the 10.6 eV UV-ionisation region of a differential mobility spectrometer. Acetone was also proposed as a charge carrier for the UV photo-ionisation source; to promote phenol protonation and inhibit charge sequestration from benzene. The responses of the system to aqueous standards of benzene and phenol with and without acetone doping at 10.2 mg m(-3) were evaluated and four to five-fold increases in sensitivity were obtained with acetone doping. With a sampling time of 60 s and a total measurement cycle of 180 s it was possible to obtain quantitative responses to single standards over the concentration range 6 to 177 microg cm(-3) with linear correlations with R(2) values ranging from 0.97 to 0.99. The effects of the heating rate of the membrane and the dispersion field strength of the differential mobility spectrometer on sensitivity and the differentiation of benzene from phenol responses were optimised, leading to a configuration where a voltage heating programme of 4.75 V s(-1) was applied to a 124 microm stainless steel wire heating element within the active membrane, and a dispersion field strength of 22 kV cm(-1) was used to test a mixture of benzene (14 microg cm(-3)) and phenol (6 microg cm(-3)) in water. The presence of benzene was identified through the presence of a peak corresponding to a benzene response, V(C) = -9 V FWHM = 1 V, that followed the thermal desorption profile of benzene.     

On-line monitoring by membrane introduction mass spectrometry of chlorination of organics in water. Mechanistic and kinetic aspects of chloroform formation

Chloroform formation during the chlorination of simple organic molecules modeling humic substances, such as phenol and di- and trihydroxybenzenes, was studied by on-line membrane introduction mass spectrometry (MIMS). Under the reaction conditions employed, chloroform was rapidly formed from 1,3-dihydroxybenzene, 1, 4-dihydroxybenzene, phenol and 1,2,3-trihydroxybenzene with yields of 17, 13, 7 and 5%, respectively. With the exception of aniline, which afforded a 17% chloroform yield, non-phenolic compounds, such as nitrobenzene, chlorobenzene, toluene, benzene and cyclohexanol, furnished low yields. Mechanistic studies showed that phenol is chlorinated consecutively and produces initially chlorophenol. It is suggested that chloroform might be formed mainly from chlorinated 3, 5-cyclohexadienone-type intermediates. MIMS was also used to determine the reaction rates and to study the kinetics of the chlorination. A good Hammett linear correlation for an electrophilic substitution mechanism was found for the compounds C(6)H(5)X (X = NH(2), OH, CH(3), H, Cl and NO(2)).     

Modeling synergistic adsorption of phenol/aniline mixtures in the aqueous phase onto porous polymer adsorbents

The adsorption equilibria of phenol and aniline on nonpolar polymer adsorbents (NDA-100, XAD-4, NDA-16 and NDA-1800) were investigated in single- and binary-solute adsorption systems at 313 K. The results showed that all the adsorption isotherms of phenol and aniline on these adsorbents can be well fitted by Freundlich and Langmuir equations, and the experimental uptake of phenol and aniline in all binary-component systems is obviously higher than predicted by the extended Langmuir model, arising presumably from the synergistic effect caused by the laterally acid-base interaction between the adsorbed phenol and aniline molecules. A new model (MELM) was developed to quantitatively describe the synergistic adsorption behavior of phenol/aniline equimolar mixtures in the binary-solute systems and showed a marked improvement in correlating the binary-solute adsorption of phenol and aniline by comparison with the widely used extended Langmuir model. The newly developed model confirms that the synergistic coefficient of one adsorbate is linearly correlated with the adsorbed amount of the other, and the larger average pore size of adsorbent results in the greater synergistic effect of phenol/aniline equimolar mixtures adsorption.