溴化正丁基吡啶增敏2'-羟基查耳酮的碱催化环化反应研究

考察了溴化N-烷基吡啶存在下的2'-羟基查耳酮碱催化环化反应及动力性质.结果表明,溴化正丁基吡啶能有效促进NaOH催化2'-羟基查耳酮转化为黄烷酮,在室温下反应2h,黄烷酮产率达89.4%;碱催化环化反应为一级反应,当溴化正丁基吡啶作增敏剂时,该反应的表观活化能将从161.9KJ/mol降至18.07KJ/mol.     

新型黄烷酮的合成及其抑菌活性

以异香草醛和2,4,6-三羟基苯乙酮为起始原料,经过C-异戊烯基化、选择性地甲基化或甲氧甲基化、羟醛缩合、催化环化与加成共6步反应,首次合成了两个新型黄烷酮—5,7,4'-三甲氧基-3'-羟基-8-(3”-羟基-3”-甲基-丁基)黄烷酮(1a)和5,7,4'-三甲氧基-3'-羟基-8-(3”,甲氧基-3”-甲基-丁基)...     

由2'''',4''''-二氢-6''''-甲氧基-3'''',5''''-二甲基查耳酮合成新黄酮

在DMSO/ I2的氧化作用下,由2',4'-二氢-6'-甲氧基-3',5'-二甲基查耳酮可合成一种全新结构的黄酮:7-羟基-5-甲氧基-6,8-二甲基黄酮(产率91%),而在HCl/MeOH作用下则得到了两种黄烷酮:7-羟基-5-甲氧基-6,8-二甲基黄烷酮 (产率70%) 和 5,7-二羟基-6,8-二甲基黄烷酮 (产率20%).     

(±)胡枝子黄烷酮-A的全合成

胡枝子黄烷酮-A为6,8-二(γ,γ-二甲基烯丙基)-4'-甲氧基-5,7,2'-三羟基(2S)-黄烷酮(1)。本文报道了其外消旋体的全合成。     

(±) Cudraflavanone B及(±)-5-O-Methyl Cudraflavanone B的全合成研究

以2,4,6-三羟基苯乙酮和2,4-二羟基苯甲醛为起始原料, 经过异戊烯基取代、选择性保护羟基、Mitsunobu反应、Claisen重排、醛酮缩合、催化环化及去保护基等步骤, 首次完成了天然异戊烯基黄烷酮Cudraflavanone B的全合成, 同时也完成了(±)-5-O-甲基-6-(2"-异戊烯基)-7,2',4'-三羟基黄烷酮的全合成研究.     

羟基取代黄烷酮类化合物与NO的反应研究

羟基取代的黄烷酮与NO反应, 得到了羟基邻位或对位单硝基化产物. 随着反应时间的延长, 有羟基邻位和对位双硝基化以及羟基两个邻位双硝基化产物生成. 多羟基取代的黄烷酮可以生成多硝基化产物.     

3-芳基戊二酰基双(4'-苯并-15-冠-5)的合成

苯甲醛和对氯苯甲醛在碱存在下分别与4'-乙酰基苯并-15-冠-5缩合, 生成冠醚化查尔酮1a和1b. 此二化合物作为中间体进一步与4'-乙酰基苯并-15-冠-5发生Michael反应, 生成两种酮型双冠醚2a和2b.     

(±)-2-甲基-5-羟基-2-(4'-甲基-3'-戊烯基)-二氢-1-苯并吡喃黄烷酮的全合成

以2,4,6-三羟基苯乙酮和柠檬醛为起始原料,经环化、保护酚羟基、羟醛缩合、脱保护、催化环化等反应以5.9%的总产率完成了天然产物(±)-2-甲基-5-羟基-2-(4'-甲基-3'-戊烯基)-二氢-1-苯并吡喃黄烷酮的全合成,其结构经1H NMR,13C NMR和HR-ESI-MS确证。     

辅酶Q10的合成

以2,3,4,5-四甲氧基甲苯为原料, 经溴化、生成格氏试剂后在碘化亚铜存在下与(E)-4-氯-2-甲基-1-苯磺酰基-2-丁烯缩合得到合成辅酶Q10的关键中间体6-(E-3'-甲基-4'-苯磺酰基-2'-丁烯基)-2,3,4,5-四甲氧基甲苯. 此中间体与茄尼基溴缩合、脱砜基化反应和氧化三步反应, 最终制得标题化合物辅酶Q10, 以2,3,4,5-四甲氧基甲苯计总收率达31.3%.     

一种新型有机-无机杂化介孔碱性催化材料的合成与表征

通过直接合成方法, 制备了胺基功能化的HMS型有机无机杂化介孔碱性催化材料(Amx-HMS).采用粉末X射线衍射分析、透射电镜、氮气吸附-脱附、29Si固体核磁共振、 红外光谱和元素分析等方法对合成材料进行了表征. 通过典型的2'-羟基苯基甲基酮和苯甲醛缩合制备黄烷酮的反应对其碱催化活性中心进行了表征.     

Thermal degradation of copolymers of styrene and acrylonitrile. II. Reaction products

Hydrogen cyanide is a minor product of degradation of copolymers of styrene and acrylonitrile. The liquid products have been separated and identified by combined gas chromatography and mass spectrometry (GC-MS), as styrene, acrylonitrile, toluene, and benzene. The ratio of styrene to acrylonitrile monomers in the products is approximately twice that of the monomer units in the copolymers, and the ratios of styrene to toluene and benzene are the same as are obtained from pure polystyrene. These ratios were determined by using infrared spectral methods. The fraction of products volatile at the temperature of degradation but involatile at ambient temperature was also analyzed by using GC-MS. A series of four dimers and four trimers were fairly reliably identified. The residual material from copolymers containing up to 33.4% acrylonitrile is always soluble in toluene. The 50/50 copolymer and its residues are insoluble in toluene. Yellow coloration develops in the residues from high acrylonitrile copolymers at advanced stages of degradation. Infrared and ultraviolet spectra suggest that this is due to conjugated unsaturation in the polymer chain backbone which may be associated with the liberation of hydrogen cyanide from the acrylonitrile units.     

A theoretical study on the destruction of typical biomass tar components (toluene,phenol and naphthalene) by OH radical

The detailed reaction mechanism of OH radical destroying toluene, phenol and naphthalene was studied through quantum chemical calculations in the research. Theoretical results indicate that for phenol and toluene, OH radical preferentially attack the ortho C atom due to the functional group on the benzene ring. But for naphthalene, OH radical preferentially attack the para-position C atoms because of its inherent benzo structure. To further study of the kinetics, the rate constant was calculated by the transition state theory. The comparison shows that the theoretical reaction rate constants for the degradation of tar by the OH radical were consistent with those obtained from literature experiments. And the rate constant of destructing naphthalene by OH radical was larger than that of destructing toluene, but lower than that of destructing phenol. The degradation sequence of OH radical to tar is: phenol ​> ​naphthalene ​> ​toluene. Because of the activation of hydroxyl group in benzene ring, phenol is the most easily attacked and destroyed by OH radical. The theoretical results can provide theoretical basis and data reference for further research on the removal of biomass tar and aromatics by OH radical.     

具有独特电子结构的锌掺杂SnO2介导形成氧空位实现高效稳定的光催化降解甲苯

室内家具和工业生产排放的挥发性有机化合物(VOCs)是典型的空气污染物,对环境和人类健康造成严重威胁.然而,目前广泛应用的二氧化钛(P25)光催化剂在降解VOCs,尤其是降解芳香烃的过程中,存在光催化转化率低,失活快等问题.因此,开发具有高效和稳定性的新型光催化剂来降解VOCs,并将其实际应用是重要的科学问题.SnO₂是一种稳定无毒的半导体光催化剂,但电子和空穴的复合率较高.掺杂过渡金属离子后可以提供缺陷态来抑制催化剂电子空穴对的快速复合,促进界面电荷转移.相比其他金属离子,Zn²⁺与Sn⁴⁺的离子半径非常相近,因此Zn²⁺会很容易掺杂到SnO₂晶格中.并且用Zn²⁺取代Sn⁴⁺会形成表面修饰,即形成更多的氧空位(SOVs)来补偿正电荷.氧空位的存在不仅会产生缺陷能级,而且还可以促进大量局域电子的累积.SnO₂上氧空位和Zn掺杂结构的协同作用可以弥补单一的外源离子掺杂或产生氧空位的不足.因此,本文采用一种简便的一步法合成催化剂Zn-SnO₂,即在SnO₂上同时实现Zn掺杂和形成SOVs,利用两者对SnO₂的协同作用提高电荷转移和分离效率,使其在低或高相对湿度条件下均表现出高效、稳定的光催化降解甲苯性能.采用低温固态电子顺磁共振(EPR)检测了催化剂中的氧空位,在纯SnO₂中仅检测到弱的EPR信号,而Zn-SnO₂上的EPR信号非常强,表明Zn²⁺的掺杂诱导产生了大量的氧空位.扫描电镜和透射电镜结果表明,掺杂Zn²⁺可以有效抑制SnO₂纳米粒子的晶体生长和相变,使得掺杂Zn²⁺的SnO₂粒子的粒径显著减小,从而导致SOVs含量增加,此外粒径的减小有利于增大其比表面积,增加活性吸附位点.紫外可见漫反射结果表明,Zn-SnO₂拓宽了光吸收范围,这归因于锌掺杂和氧空位的协同作用.在紫外光照射下,Zn-SnO₂的光催化降解甲苯性能优于纯SnO₂和P25,降解率达到77.5%.ESR光谱结果表明,Zn-SnO₂上的电子自旋共振信号强度均强于纯SnO₂和P25,说明Zn-SnO₂具有较好的氧化能力,也与DFT计算O₂和H₂O的吸附能结果相吻合,表明了锌掺杂和SOVs对SnO₂的协同作用可以显著提高电荷转移和分离效率.最后,通过原位红外光谱和DFT计算方法对甲苯降解的机理进行了研究.结果表明,甲苯的苯环在纯SnO₂表面倾向于在苯甲酸阶段打开,在Zn-SnO₂表面更倾向于在苯甲醛阶段选择性地开环.可见,Zn-SnO₂光催化剂缩短了甲苯的降解路径,并能显著抑制中间毒副产物产生.综上,本工作提供了一种安全,高效和可持续的降解VOCs的光催化剂.     

Enzyme-catalysed synthesis and absolute configuration assignments of cis-dihydrodiol metabolites from 1,4-disubstituted benzenes

A series of ten cis-dihydrodiol metabolites has been obtained by bacterial biotransformation of the corresponding 1,4-disubstituted benzene substrates using Pseudomonas putida UV4, a source of toluene dioxygenase (TDO). Their enantiomeric excess (ee) values have been established using chiral stationary phase HPLC and 1H NMR spectroscopy. Absolute configurations of the majority of cis-dihydrodiols have been established using stereochemical correlation and X-ray crystallography and the remainder have been tentatively assigned using NMR spectroscopic methods but finally confirmed by circular dichroism (CD) spectroscopy. These configurational assignments support and extend the validity of an empirical model, previously used to predict the preferred stereochemistry of TDO-catalysed cis-dihydroxylation of ten 1,4-disubstituted benzene substrates, to more than twenty-five examples.     

超临界苯类溶剂对聚苯乙烯降解的影响

在高压间歇反应器中,温度340~370℃,以苯、甲苯、乙苯和对二甲苯为超临界溶剂研究了聚苯乙烯(PS)的降解特性.苯类物质是聚苯乙烯的优良溶剂,在超临界条件下其优异的传质、传热性能使聚苯乙烯快速降解.聚苯乙烯在不同超临界溶剂中降解转化率相近,而降解产物组成差别很大,分析了不同超临界溶剂对聚苯乙烯降解过程的影响.结果表明超临界甲苯对降解过程影响最小,苯乙烯收率最高.聚苯乙烯降解过程中,高分子链断裂和解聚同时进行,结合连续分布理论建立了聚苯乙烯降解的动力学模型,得到在超临界甲苯中聚苯乙烯链端解聚活化能为138.4 kJ.mol-1.     

Determination of benzylsuccinic acid in gasoline-contaminated groundwater by solid-phase extraction coupled with gas chromatography-mass spectrometry

Benzylsuccinic acid (BSA) and methylbenzylsuccinic acid (methyl-BSA) are unambiguous biotransformation products resulting from anaerobic toluene and xylene biodegradation, respectively. A solid-phase extraction method based on polystyrene-divinylbenzene sorbent was developed for the quantitative BSA determination in groundwater samples as an alternative to liquid-liquid extraction. Gas chromatography coupled with mass spectrometry was used for separation and detection. The recovery from spiked 11 groundwater samples was 88 to 100%. The precision of the method, indicated by the relative standard deviation, was +/- 4% and the method detection limit was 0.2 microg/l. The concentration of BSA and methyl-BSA in groundwater samples from anaerobic BTEX (benzene, toluene, ethylbenzene and xylenes)-contaminated sites ranged from below the detection limit (3 microg/l) to 155 microg/l.     

LED照射光催化剂用于苯、甲苯、乙苯和二甲苯分解(英文)

Studies on the use of gas phase applications of light emitting diodes(LEDs) in photocatalysis are scarce although their photocatalytic decomposition kinetics of environmental pollutants are likely different from those in aqueous solutions.The present study evaluated the use of chips of visible light LEDs to irradiate nitrogen doped titania(N-TiO2) prepared by hydrolysis to decompose gaseous benzene,toluene,ethyl benzene,m-xylene,p-xylene,and o-xylene.Photocatalysts calcined at different temperatures were characterized by various analytical instruments.The degradation efficiency of benzene was close to zero for all conditions.For the other compounds,a conventional 8 W daylight lamp/N-TiO2 unit gave a higher photocatalytic degradation efficiency as compared with that of visible-LED/N-TiO2 units.However,the ratios of degradation efficiency to electric power consumption were higher for the photocatalytic units that used two types of visible-LED lamps(blue and white LEDs).The highest degradation efficiency was observed with the use of a calcination temperature of 350 oC.The average degradation efficiencies for toluene,ethyl benzene,m-xylene,p-xylene,and o-xylene were 35%,68%,94%,and 93%,respectively.The use of blue-and white-LEDs,high light intensity,and low initial concentrations gave high photocatalytic activities for the photocatalytic units using visible-LEDs.The morphological and optical properties of the photocatalysts were correlated to explain the dependence of photocatalytic activity on calcination temperature.The results suggest that visible-LEDs are energy efficient light source for photocatalytic gas phase applications,but the activity depends on the operational conditions.     

Carbon isotope fractionation of benzene and toluene by progressive evaporation

Evaporation is one of the key attenuation processes for near‐surface volatile organic compounds (VOCs) in the upper soil zone. Evaporation experiments were performed to investigate the carbon isotope fractionation of benzene and toluene during progressive and non‐equilibrium evaporation at room temperature. Considerable carbon isotope fractionation occurred during evaporative enrichment of benzene and toluene. The carbon isotope compositions of residual compounds increased exponentially with increasing evaporation. Thus, the remaining liquids become isotopically heavier, and the process follows a Rayleigh trend. This result is compatible with the direction of isotopic changes associated with both microbial degradation and volatilization of hydrocarbons previously observed in soil columns, but shows exactly the opposite behavior to previous equilibrium volatilization findings. Copyright © 2010 John Wiley & Sons, Ltd.     

Catalytic transformation of methane over in-loaded ZSM-5 zeolite in the presence of ethene

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.     

Degradation products generated by sonication of benzyl alcohol, a sample preparation solvent for the determination of residual solvents in pharmaceutical bulks, on capillary gas chromatography

Benzyl alcohol used as the sample preparation solvent in the determination of residual solvents in pharmaceutical bulks yielded benzene, toluene, and benzaldehyde on capillary gas chromatography (GC) by sonication. The factors responsible for compounds generated are discussed. The quality of benzyl alcohol and the type of sonicator were not involved in the generation of benzene, toluene, and benzaldehyde, whereas matrix contributions were observed. The degradation profiles of benzyl alcohol and its analogous compounds obtained by pyrolysis-GC/mass spectrometric analysis were similar to those obtained by sonication, suggesting that benzyl alcohol is degraded by the high local heat generated by sonication. Consequently, no matter how long it may take to dissolve bulk substances in benzyl alcohol completely, we do not recommend the use of a sonicator in sample preparation for the determination of residual solvents in pharmaceutical bulks.