无机化学微信平台的构建与实践研究

针对无机化学传统教学模式的不足,构建了无机化学微信平台。介绍了构建平台必需的微信公众号和微信群的建立过程和方法。分析了无机化学微信平台在教学中的实践效果,弥补了传统教学中的不足。讨论了无机化学微信平台的积极作用,提高了教师教学水平和学生的学习能力,达到了师生双赢的目的。     

非理想气体的逸度因子和非理想溶液的活度系数

对单组分非理想气体,推导了它的逸度因子的微分方程式。对多组分非理想气体,推导了各组分逸度因子满足的微分方程式,定义了一个总逸度因子,并找到了总逸度因子和各组分逸度因子之间的关系。同样,对非理想溶液,推导了各组分活度系数满足的微分方程式,定义了非理想溶液的总活度系数,并找到了两者满足的关系。最后分析了逸度因子和活度系数之间的异同点。     

木质素资源利用的研究进展

木质素作为一种大量存在的可再生资源,具有巨大的应用潜力。近年来,木质素资源的高效利用问题引起了人们的广泛关注。本文综述了近几年来国内外木质素资源利用的研究状况,简要介绍了木质素利用的两种方式:大分子形式利用以及液化降解利用。重点介绍了木质素液化降解制备生物油及酚类化合物的国内外研究现状,并对液化降解机理进行了阐述。最后,总结了当前木质素资源利用存在的问题,提出了未来木质素利用的研究方向,展望了木质素的发展前景。     

新解色谱现象

在客观分析色谱现象的基础上对色谱分离机理的传统解释提出了质疑和否定,并对色谱分离机理作出了新的解释。通过对色谱现象的研究和分析,不仅确定了一条流体运动的基本规律,还对固定相赋予了新的内涵,提出了能量场固定相的设想。由于对色谱分离原理进行了新的解释,因此对色谱现象提出了一个新的定义。     

Pickering乳状液的研究进展

随着纳米技术的发展以及Pickering乳液在食品、化妆品、医药等领域的潜在应用前景,人们对Pickering乳液给予了关注。本文全面总结了近些年来Pickering乳液的研究进展,对本课题组在Pickering乳液研究领域所取得的成果进行了介绍。本文主要分为4个部分:第一部分概述了Pickering乳液的研究现状;第二部分全面考察了Pickering乳液的各种影响因素;第三部分介绍了Pickering乳液的转相特性;最后综述了颗粒和表面活性物质协同稳定乳液的研究进展。这些研究成果促进了乳液基础理论的发展,并且拓展了乳液的应用范围。     

石墨烯:从理论模型到客观实在

2004年石墨烯的出现倾覆了二维碳材料不能稳定存在的传统理论,创建了从零维到三维的碳范式。通过对石墨烯发现史的考证可知,19世纪40年代,科学家们对氧化石墨进行了大量的研究。这些研究促进了石墨烯的发现。20世纪50年代,理论物理学家就对石墨烯的存在做出了理论假设。至20世纪80年代,科学家对碳的同素异形体进行了大量的探索,为制备单层石墨烯不懈奋斗。经历了多次的失败后,研究者最终在2004年成功制备出石墨烯并研究其特性。石墨烯的发现带来了人们科学认识上的转变,同时也带来了技术领域的突破。     

分析化学实验课程教学大纲的标准化改造与构建

基于工程教育专业认证标准的要求,结合专业课程的特点,对我校制药工程专业的分析化学实验教学大纲进行了标准化改造。标准化的教学大纲更加突出了专业适用性,关联了教学要求与教学内容和考核评定,增加了考核量化指标与课程持续改进的方式,进一步规范了分析化学实验课程的教学。标准教学大纲的构建为实验教学活动提供了更加明确的指导,有利于缩小不同教师教学的差异性,保证了实验教学的质量,为建立可持续完善的工程类实验教学标准体系提供了具体参考。     

天然产物Diazonamide A的全合成研究进展

综述了海洋天然产物Diazonamide A全合成的研究进展，分析了各合成路线的关键步骤，讨论了各方法的特点。简单描述了Diazonamide A类似物构效关系的研究成果。参考文献17篇。     

硫的同素异形体*

硫是固态同素异形体数量最多的元素。但就单质硫的同素异形体而言,教材中并没有详细概述。根据硫化学的研究进展,全面考察了硫的同素异形体的种类,讨论了它们的制备、晶体结构及其相互转化,着重体现了科学技术对其同素异形体扩展的重要作用,完善了硫同素异形体在教学中的深入介绍。同时,也体现了科学研究对本科教学内容改革的推进作用。     

声发射和激光拉曼研究镍氧化机制中的稀土元素效应

对纯镍及其表面离子注钇样品在1000℃空气中的恒温氧化和循环氧化行为进行了研究。用扫描电镜(SEM)和透射电镜(TEM)对氧化膜的表面形貌及结构进行了观测。研究表明离子注钇极大地提高了金属镍的抗氧化性能。此外,用声发射(AE)技术研究了氧化膜／基体界面上缺陷的分布情况,并用激光拉曼(Raman)谱对注钇引起的膜内应力变化进行了测量。结果表明,离子注钇降低了NiO氧化膜的生长速率,减小了表面NiO的晶粒尺寸,降低了膜内压应力水平。同时,离子注钇还减小了氧化膜／基体界面缺陷的平均尺寸和数目,因此,极大地提高了镍表面NiO氧化膜的粘附性和保护性。     

Theoretical study of reactant activation in 1,3-dipolar cycloadditions of cyclic nitrones to free and Pt-bound nitriles

[reaction: see text] 1,3-Dipolar cycloaddition of the cyclic nitrones CH2(CH2)2CH=NO (N1), CH2CH2OCH=NO (N2), CH2-OCH2CH=NO (N3), and O(CH2)2CH=NO (N4) to organonitriles, RCN-both free (R = CH(3), CF(3)) and ligated to Pt(II) and Pt(IV) (in the complexes trans-[PtCl(2)(NCCH(3))(2)] (1) and trans-[PtCl(4)(NCCH(3))(2)] (2))-was investigated extensively by theoretical methods at different levels of theory. The effectiveness of two types of dipolarophile activation (by introducing a strong electron-acceptor group R and by coordination to a metal center) was analyzed and compared. The influence of factors such as the nature of the cyclic nitrone and the nature of the solvent on the reactions was also studied. The reactivity of dipoles and dipolarophiles increases along the series N4 < N1 approximately N3 < N2 and CH(3)CN < CF(3)CN < 1 < 2; the latter demonstrates that the coordination of RCN to a Pt center provides an even higher activation effect upon cycloaddition in comparison with the introduction of a strong electron-acceptor group R such as CF(3). A higher reactivity of the cyclic dipole N1 in comparison with acyclic nitrones (e.g., CH(3)CH=N(CH(3))O) is interpreted to be a result of its exclusive existence in a more strained and hence more reactive E- rather than Z-configuration. The activation and reaction energies have been calculated at different basis sets and levels of theory, up to MP4(SDTQ), CCSD(T), and CBS-Q. The activation energies are weakly sensitive to a change of the correlated methods. The consideration of the solvent effects results in the increase of the activation barriers, and such enhancement is less pronounced for the nonpolar or low polar solvents. The cycloadditions to CH(3)CN and CF(3)CN were found to be nearly synchronous, but these reactions involving 1 and 2 are clearly asynchronous. Moreover, the reaction of N2 with 2 proceeds via a very early acyclic transition state, while for all other reactions the transition states have a cyclic nature.     

锶掺杂对氧化镧催化甲烷氧化偶联反应的影响

甲烷氧化偶联反应(OCM)是天然气直接转化利用的重要途径之一.该反应通过甲烷和氧气在催化剂作用下一步将甲烷直接转化为乙烯等具有高附加值的产品,避免了涉及高能耗过程的合成气间接路径,不仅有可能减少中间副产物的生成,还有可能大大提升整个过程的能源利用效率.因此,研究OCM反应具有十分重要的实际意义.目前氧化镧基催化剂具有良好的催化活性、产物选择性和热稳定性,但在OCM反应中产品收率仍未能达到工业应用的要求,因而近几十年来高效OCM催化剂的研发一直是研究热点.实验发现,锶掺杂氧化镧催化剂具有更为优异的催化性能,主要表现在具有比纯氧化镧催化剂更高的催化活性和产物选择性,但对于锶掺杂的影响机制仍然缺乏系统的理论研究.目前普遍认为,甲烷活化是OCM反应的第一步,也是决速步,这主要是由于C?H键活化需要越过很高的能垒,因此往往需要很高的温度.本文主要采用团簇模型,通过密度泛函理论计算来研究OCM反应中锶掺杂对氧化镧催化剂上甲烷活化性能的影响及其作用原理.本文构建了八种锶掺杂的氧化镧团簇作为该催化剂模型,可分为没有自由基性质的团簇(LaSrO2(OH),La2SrO4,La3SrO5(OH),La5SrO8(OH))和具有自由基性质的团簇(LaSrO3,La2SrO4(OH),La3SrO6,La5SrO9).我们计算了甲烷在这些锶掺杂氧化镧团簇上Sr?O和La?O酸碱对位点以及氧自由基活性位点上的活化机制,以研究锶掺杂对OCM反应活性的影响,并与我们前期计算的纯氧化镧团簇上甲烷活化性能进行了对比.通过计算甲烷在不同锶掺杂氧化镧团簇上的物理和化学吸附能、活化能垒以及甲基自由基的脱附能,发现锶掺杂氧化镧团簇上的甲烷活化在热力学和动力学上都要比纯氧化镧团簇上更为有利.对于具有相同金属原子数目的团簇,甲烷在La?O上活化的能垒大小为:化学计量比的La?Sr?O团簇<非化学计量比的La?Sr?O团簇<化学计量比的La?O团簇;而甲烷在Sr?O上活化的能垒大小依次是:化学计量比的La?Sr?O团簇<非化学计量比的La?Sr?O团簇.给定一个锶掺杂氧化镧团簇,甲烷在不同活化位点上的活化能垒大小通常是:O·<相似文献   

Reactivity of chemisorbed oxygen atoms and their catalytic consequences during CH4-O2 catalysis on supported Pt clusters

Kinetic and isotopic data and density functional theory treatments provide evidence for the elementary steps and the active site requirements involved in the four distinct kinetic regimes observed during CH(4) oxidation reactions using O(2), H(2)O, or CO(2) as oxidants on Pt clusters. These four regimes exhibit distinct rate equations because of the involvement of different kinetically relevant steps, predominant adsorbed species, and rate and equilibrium constants for different elementary steps. Transitions among regimes occur as chemisorbed oxygen (O*) coverages change on Pt clusters. O* coverages are given, in turn, by a virtual O(2) pressure, which represents the pressure that would give the prevalent steady-state O* coverages if their adsorption-desorption equilibrium was maintained. The virtual O(2) pressure acts as a surrogate for oxygen chemical potentials at catalytic surfaces and reflects the kinetic coupling between C-H and O═O activation steps. O* coverages and virtual pressures depend on O(2) pressure when O(2) activation is equilibrated and on O(2)/CH(4) ratios when this step becomes irreversible as a result of fast scavenging of O* by CH(4)-derived intermediates. In three of these kinetic regimes, C-H bond activation is the sole kinetically relevant step, but occurs on different active sites, which evolve from oxygen-oxygen (O*-O*), to oxygen-oxygen vacancy (O*-*), and to vacancy-vacancy (*-*) site pairs as O* coverages decrease. On O*-saturated cluster surfaces, O*-O* site pairs activate C-H bonds in CH(4) via homolytic hydrogen abstraction steps that form CH(3) groups with significant radical character and weak interactions with the surface at the transition state. In this regime, rates depend linearly on CH(4) pressure but are independent of O(2) pressure. The observed normal CH(4)/CD(4) kinetic isotope effects are consistent with the kinetic-relevance of C-H bond activation; identical (16)O(2)-(18)O(2) isotopic exchange rates in the presence or absence of CH(4) show that O(2) activation steps are quasi-equilibrated during catalysis. Measured and DFT-derived C-H bond activation barriers are large, because of the weak stabilization of the CH(3) fragments at transition states, but are compensated by the high entropy of these radical-like species. Turnover rates in this regime decrease with increasing Pt dispersion, because low-coordination exposed Pt atoms on small clusters bind O* more strongly than those that reside at low-index facets on large clusters, thus making O* less effective in H-abstraction. As vacancies (*, also exposed Pt atoms) become available on O*-covered surfaces, O*-* site pairs activate C-H bonds via concerted oxidative addition and H-abstraction in transition states effectively stabilized by CH(3) interactions with the vacancies, which lead to much higher turnover rates than on O*-O* pairs. In this regime, O(2) activation becomes irreversible, because fast C-H bond activation steps scavenge O* as it forms. Thus, O* coverages are set by the prevalent O(2)/CH(4) ratios instead of the O(2) pressures. CH(4)/CD(4) kinetic isotope effects are much larger for turnovers mediated by O*-* than by O*-O* site pairs, because C-H (and C-D) activation steps are required to form the * sites involved in C-H bond activation. Turnover rates for CH(4)-O(2) reactions mediated by O*-* pairs decrease with increasing Pt dispersion, as in the case of O*-O* active structures, because stronger O* binding on small clusters leads not only to less reactive O* atoms, but also to lower vacancy concentrations at cluster surfaces. As O(2)/CH(4) ratios and O* coverages become smaller, O(2) activation on bare Pt clusters becomes the sole kinetically relevant step; turnover rates are proportional to O(2) pressures and independent of CH(4) pressure and no CH(4)/CD(4) kinetic isotope effects are observed. In this regime, turnover rates become nearly independent of Pt dispersion, because the O(2) activation step is essentially barrierless. In the absence of O(2), alternate weaker oxidants, such as H(2)O or CO(2), lead to a final kinetic regime in which C-H bond dissociation on *-* pairs at bare cluster surfaces limit CH(4) conversion rates. Rates become first-order in CH(4) and independent of coreactant and normal CH(4)/CD(4) kinetic isotope effects are observed. In this case, turnover rates increase with increasing dispersion, because low-coordination Pt atoms stabilize the C-H bond activation transition states more effectively via stronger binding to CH(3) and H fragments. These findings and their mechanistic interpretations are consistent with all rate and isotopic data and with theoretical estimates of activation barriers and of cluster size effects on transition states. They serve to demonstrate the essential role of the coverage and reactivity of chemisorbed oxygen in determining the type and effectiveness of surface structures in CH(4) oxidation reactions using O(2), H(2)O, or CO(2) as oxidants, as well as the diversity of rate dependencies, activation energies and entropies, and cluster size effects that prevail in these reactions. These results also show how theory and experiments can unravel complex surface chemistries on realistic catalysts under practical conditions and provide through the resulting mechanistic insights specific predictions for the effects of cluster size and surface coordination on turnover rates, the trends and magnitude of which depend sensitively on the nature of the predominant adsorbed intermediates and the kinetically relevant steps.     

Sigma bond activation by cooperative interaction with s2 atoms: B+ + nCH4, n = 1, 2

Ab initio investigations at the MP2 and CCSD(T) level with augmented double and triple zeta basis sets have identified various stationary points on the B+/nCH4, n = 1, 2 hypersurfaces. The electrostatic complexes show a strong variation in the sequential binding energy with De for the loss of one CH4 molecule calculated to be 16.5 and 6.8 kcal mol-1 for the n = 1 and n = 2 complexes, respectively. The covalent molecular ion, CH3BH+, is found to have the expected C3 nu geometry and to be strongly bound by 84.0 kcal mol-1 with respect to B+ + CH4. The interaction of CH4 with CH3BH+ is qualitatively very similar to the interaction of CH4 with HBH+, however, the binding is only about 50% as strong due to the electron donating characteristic of the methyl group. Of particular interest are the insertion transition states which adopt geometries allowing the B+ ion to interact with multiple sigma bonds. In the n = 1 case, the interaction with two CH bonds lowers the insertion activation energy by about 25 kcal mol-1 from that expected for a mechanism involving only one sigma bond. For n = 2, B+ interacts with two CH sigma bonds from one CH4 and one CH sigma bond from the other CH4 leading to an additional activation energy decrease of about 15.7 kcal mol-1 relative to B+ + nCH4.     

Comparison of steric and electronic requirements for C-C and C-H bond activation. Chelating vs nonchelating case

C-H bond activation was observed in a novel PCO ligand 1 (C(6)H(CH(3))(3)(CH(2)OCH(3))(CH(2)P(t-Bu)(2))) at room temperature in THF, acetone, and methanol upon reaction with the cationic rhodium precursor, [Rh(coe)(2)(solv)(n)()]BF(4) (solv = solvent; coe = cyclooctene). The products in acetone (complexes 3a and 3b) and methanol (complexes 4a and 4b) were fully characterized spectroscopically. Two products were formed in each case, namely those containing uncoordinated (3a and 4a) and coordinated (3b and 4b) methoxy arms, respectively. Upon heating of the C-H activation products in methanol at 70 degrees C, C-C bond activation takes place. Solvent evaporation under vacuum at room temperature for 3-4 days also results in C-C activation. The C-C activation product, ((CH(3))Rh(C(6)H(CH(3))(2)(CH(2)OCH(3))(CH(2)P(t-Bu)(2))BF(4)), was characterized by X-ray crystallography, which revealed a square pyramidal geometry with the BF(4)(-) anion coordinated to the metal. Comparison to the structurally similar and isoelectronic nonchelating Rh-PC complex system and computational studies provide insight into the reaction mechanism. The reaction mechanism was studied computationally by means of a two-layer ONIOM model, using both the B3LYP and mPW1K exchange-correlation functionals and a variety of basis sets. Polarization functions significantly affect relative energetics, and the mPW1K profile appears to be more reliable than its B3LYP counterpart. The calculations reveal that the electronic requirements for both C-C and C-H activation are essentially the same (14e intermediates are the key ones). On the other hand, the steric requirements differ significantly, and chelation appears to play an important role in C-C bond activation.     

叔－丁基醚热分解反应的量子化学研究

用ＡＭ１方法研究了叔－丁基醚热分解反应，发现这类化合物可经过四元环过渡态分解成丁烯和醇或酚。     

Density functional theory analysis of the reaction pathway for methane oxidation to acetic acid catalyzed by Pd2+ in sulfuric acid

Density functional theory has been used to investigate the thermodynamics and activation barriers associated with the direct oxidation of methane to acetic acid catalyzed by Pd2+ cation in concentrated sulfuric acid. Pd2+ cations in such solutions are ligated by two bisulfate anions and by one or two molecules of sulfuric acid. Methane oxidation is initiated by the addition of CH4 across one of the Pd-O bonds of a bisulfate ligand to form Pd(HSO4)(CH3)(H2SO4)2. The latter species will react with CO to produce Pd(HSO4)(CH3CO)(H2SO4)2. The most likely path to the final products is found to be via oxidation of Pd(HSO4)(CH3)(H2SO4)2 and Pd(HSO4)(CH3CO)(H2SO4)2 to form Pd(eta2-HSO4)(HSO4)2(CH3)(H2SO4) and Pd(eta2-HSO4)(HSO4)2(CH3CO)(H2SO4), respectively. CH3HSO4 or CH3COHSO4 is then produced by reductive elimination from the latter two species, and CH(3)COOH is then formed by hydrolysis of CH3COHSO4. The loss of Pd2+ from solution to form Pd(0) or Pd-black is predicted to occur via reduction with CO. This process is offset, though, by reoxidation of palladium by either H2SO4 or O2.     

Synthesis of ketonylplatinum(III) dinuclear complexes: observation of the competitive radical vs electrophilic displacement in Pt(III)-promoted C-H bond activation of ketones.

New ketonylplatinum(III) dinuclear complexes [Pt(2)((CH(3))(3)CCONH)(2)(NH(3))(4)(CH(2)COPh)](NO(3))(3) (4), [Pt(2)((CH(3))(3)CCONH)(2)(NH(3))(4)(CH(CH(3))COC(2)H(5))](NO(3))(3) (5), and [Pt(2)((CH(3))(3)CCONH)(2)(NH(3))(4)(CH(2)COCH(2)COCH(3))](NO(3))(3) (6) were prepared by treatment of platinum blue complex [Pt(4)(NH(3))(8)((CH(3))(3)CCONH)(4)](NO(3))(5) (2) with acetophenone, 3-pentanone, and acetylacetone, respectively, in the presence of concentrated HNO(3). The structures of complexes 4 and 6 have been confirmed by X-ray diffraction analysis, which revealed that the C-H bonds of the methyl groups in acetophenone and acetylacetone have been cleaved and Pt(III)-C bonds are formed. Formation of diketonylplatinum(III) complex 6 provides a novel example of the C-H bond activation not at the central alpha-C-H but at the terminal methyl of acetylacetone. Reaction with butanone having unsymmetrical alpha-H atoms led to two types of ketonylplatinum(III) complexes [Pt(2)((CH(3))(3)CCONH)(2)(NH(3))(4)(CH(CH(3))COCH(3))](NO(3))(3) (7a) and [Pt(2)((CH(3))(3)CCONH)(2)(NH(3))(4)(CH(2)COCH(2)CH(3))](NO(3))(3) (7b) at a molar ratio of 1.7 to 1 corresponding to the C-H bond activation of methylene and methyl groups, respectively. Use of 3-methyl-2-butanone instead of butanone gave complex [Pt(2)((CH(3))(3)CCONH)(2)(NH(3))(4)(CH(2)COCH(CH(3))(2))](NO(3))(3) (8) as a sole product via C-H bond activation in the alpha-methyl group. The reactivity of the ketonylplatinum(III) dinuclear complexes toward nucleophiles, such as H(2)O and HNEt(2), was examined. The alpha-hydroxyl- and alpha-amino-substituted ketones were generated in the reactions of [Pt(2)((CH(3))(3)CCONH)(2)(NH(3))(4)(CH(2)COCH(3))](NO(3))(3) (1), 5, and a mixture of 7a and 7b with water and amine, which indicates that the carbon atom in the ketonyl group bound to the Pt(III) atom can receive a nucleophilic attack. The high electrophilicity of the ketonylplatinum(III) complexes can be accounted for by the high electron-withdrawing ability of the platinum(III) atom. A competition between the radical and electrophilic displacement pathways was observed directly in the C-H bond activation reaction with butanone giving complexes 7a and 7b. Addition of a radical trapping agent suppressed the radical pathway and gave complex 7b as the predominant product. On the contrary, 7a was formed as the main product when the reaction solution was irradiated by mercury lamp light. These results together with other mechanistic studies demonstrate that complex 7a was produced via a radical process, whereas complex 7b is produced via electrophilic displacement of a proton by the Pt(III) atom. The competitive processes were further observed in the reactions of platinum blue complex 2 with a mixture of acetone and 3-pentanone in the presence of HNO(3). The relative molar ratio of acetonyl complex 1 to pentanoyl complex 5 was 3 to 1 under room light, whereas formation of complex 5 was almost suppressed when the reaction was carried out in the dark with the addition of a radical trapping agent.     

Ni/γ-Al2O3催化剂上CH4-CO2重整体系中积碳-消碳的研究

用动态热重技术和色谱技术联用以及XRD和TEM等表征手段,研究了Ni/γ-Al2O3催化剂上甲烷－二氧化碳重整体系的积碳和消碳及其与一氧化碳产率之间的关系。结果表明,二氧化碳与甲烷有不同的活性中心,二氧化碳的存在不改变甲烷活化积碳的本质,但可通过及时将表面含碳物种转化为一氧化碳而降低积碳速率,二氧化碳能消去活泼的须状碳,但不易消去惰性的石墨碳。等摩尔条件下二氧化碳消碳能力弱于甲烷活化积碳,二氧化碳适度过量可有效抑制积碳,n(CO2)/n(CH4)≈1.3为进料比最佳值,此时积碳－消碳达到动态平衡,可获得最高的一氧化碳产率和较低的积碳速率,且该值不受温度影响。Ni/γ-Al2O3催化剂有很强的再生能力,但反复积碳－消碳会使催化剂镍晶粒度增大,分散度下降,从而导致不可逆失活。     

Reactions of methane with titanium atoms: CH3TiH, CH2=TiH2, agostic bonding, and (CH3)2TiH2

Laser-ablated titanium atoms react with methane to form the insertion product CH3TiH, which undergoes a reversible photochemical alpha-H transfer to give the methylidene complex CH2=TiH2. On annealing a second methane activation occurs to produce (CH3)2TiH2. These molecules are identified from matrix infrared spectra by isotopic substitution (CH4, 13CH4, CD4, CH2D2) and comparison to DFT frequency calculations. The computed planar structure for singlet ground-state CH2=TiH2 shows CH2 distortion and evidence for agostic bonding (H-C-Ti, 91.4 degrees), which is supported by the spectra for CHD=TiHD.