光促进下N,N-二甲基甲酰胺作为一氧化碳源的烯烃氢酯化反应

 研究了光照下以N,N-二甲基甲酰胺(DMF)为一氧化碳源的烯烃氢酯化反应. 结果表明,在常温常压和光照射条件下DMF可以分解得到CO,新生成的CO在光促进下可以直接与CH3OH-DMF溶液中的底物1-辛烯在温和条件和非贵金属钴化合物(Co(OAc)2,CoCl2,Co(en)3Cl2和大环钴[Co(14)4,11-二烯-N4]I2)催化下进行氢酯化反应,反应中DMF既是溶剂,又是原料. H13CON(CH3)2同位素示踪实验证实了这一结果. 在反应体系中通入二氧化碳可以大大提高反应的转化率、产率及选择性. 13CO2同位素示踪实验表明,CO2并未参与产物的形成,其作用是中和DMF分解产生的HN(CH3)2,从而有利于DMF的光促分解.     

亚临界水介质回收酸酐固化环氧树脂/碳纤维复合材料

研究了不同添加剂对碳纤维增强酸酐固化环氧树脂复合材料在亚临界水中降解的影响,通过IR、GC-MS等分析,确定了环氧树脂的分解机理主要为酯键的断裂。 结果表明,KOH与苯酚对酸酐固化环氧树脂的分解没有协同效应,碱性物质更有利于酯键的断裂。 甲基四氢邻苯二甲酸酐固化的环氧树脂增强碳纤维复合材料在反应温度为250 ℃、反应时间为60 min、KOH浓度为0.2 mol/L时可完全分解,回收碳纤维的拉伸强度和表面形貌未受影响。     

多壁碳纳米管固载金鸡纳生物碱季铵盐类手性相转移催化剂的制备及其催化烷基化反应性能

制备了多壁碳纳米管(MWCNTs)固载的金鸡纳生物碱季铵盐类手性相转移催化剂PTC-1/MWCNTs,并用于催化N-二苯亚甲基-甘氨酸叔丁酯的不对称烷基化反应中.采用紫外-可见光谱系统研究了五种有机溶剂对PTC-1在MWCNTs上吸附和脱附的影响.结果表明,在甲苯中,MWCNTs对PTC-1的吸附率最高(53%),而在三氯甲烷中PTC-1的脱附率最低(仅为0.75%).PTC-1/MWCNTs催化剂在催化N-二苯亚甲基-甘氨酸叔丁酯和不同卤代烃的不对称烷基化反应中,所得产物的收率和对映体选择性都较高,而且该催化剂可回收循环使用,说明PTC-1经MWCNTs固载后,仍能够有效地催化多种卤代烃的不对称烷基化反应.     

Chemo- and stereoselectivity in titanium-mediated regioselective ring-opening reaction of epoxides at the more substituted carbon

Chemo- and stereoselectivity in the ring-opening reaction of epoxides with a reagent prepared from allylmagnesium halide and chlorotitanium triphenoxide is described. It has been proven that the allylating reagent can also be used for the reaction of epoxides bearing a tert-butyl ester, amide, or acetal moiety, and that the epoxide cleavage regioselectively takes place at the more substituted carbon in all cases. Interestingly, while the reaction of acyclic 2,2,3-trialkyl epoxides or 3,3-disubstituted 2,3-epoxy alcohol derivatives with the allyltitanium reagent yielded the allylated products as an almost 1:1 diastereomixture, the ring-opening reaction of 2-substituted 2,3-epoxy alcohol derivatives stereospecifically proceeded through the anti pathway. The latter reaction is extremely useful for asymmetric construction of quaternary carbon centers.     

磷酸活化粘胶基活性炭纤维的碳化活化机理

采用热重分析仪、红外光谱仪、X－射线衍射仪、核磁共振仪、X－射线光电子能谱仪及吸附仪等手段对磷酸浸渍粘胶纤维的碳化活性过程进行研究,实验结果表明：磷酸促进纤维素脱水,加上磷酸的阻及交联作用降低了纤维的大量裂解和碎片的逸散,使纤维的碳残留率提高。纤维素与浸渍的磷酸部分生成磷酸酯键,但它们在160℃以上逐渐分解。纤维上残留少量偏磷酸类化合物。同时纤维素基体脱水生成羰基和共轭双键,之后不断芳构化堆叠成为类石墨微晶。磷酸致孔的机理主要是磷酸珠粒的阻碍造成类石墨微晶发展不完善,堆叠时发生扭曲或形成缺陷。磷与纤维分子的酯化对微孔的生成有影响。     

异硫氰基乙酸乙酯的合成

在碱性条件下，用氨基乙酸与二硫化碳、氯甲酸乙酯反应合成了异硫氰基乙酸乙酯，总收率为48．54％。     

Covalent sidewall functionalization of single-walled carbon nanotubes by amino acids

Single-walled carbon nanotubes (SWNTs) with amino acids covalently attached to their side walls, viz., “nanotube-aminoacids,” have been prepared starting from colloidal solutions of fluorinated SWNTs (F-SWNTs) and amino acids in o-dichlorobenzene and heating at 80–150 °C in the presence of pyridine. The syntheses were carried out with the F-SWNTs of approximately 2: 1 (C: F) stoichiometry and several natural α-aino acids with both pro-tected and unprotected carboxyl groups, such as glycine ethyl ester hydrochloride, L-serine ethyl ester hydrochloride, l-cysteine, and trans-4-hydroxy-l-proline. The nanotube-aminoacids have been characterized by Raman and FTIR spectroscopy, atomic force, scanning, and transmission electron microscopies, and thermal gravimetric analysis (TGA). Based on TGA data, the degree of sidewall functionalization in the synthesized SWNT derivatives was estimated to be in the range from one of 32 to one of 8 carbon atoms, depending on the amino acid nature and reaction conditions used. The amino acid-functionalized SWNTs, prepared in this work by simple and inexpensive one-step method, can be valuable precursors for peptide synthesis and targeted drug delivery, design and fabrication of nanocomposites and fibers, and other biomedical and engineering applications. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1035–1043, May, 2008.     

Die analytische anwendung der kohlendioxyddestillationUntersuchung von dekarboxylierungsreaktionen in wässriger lösung

Carboxylic acids which decompose spontaneously on boiling or by oxidation in aqueous solutions can be determined by titration of the carbon dioxide formed after distillation as described previously. Acetonedicarboxylic acid and p-aminosalicylic acid are determined by spontaneous decarboxylation. Hydrolysis must precede the determination for acetoacetic ester, phenylethylcyanoacetic ethyl ester and for carbonic acid esters. Oxidative decarboxylation allows determinations of glyoxylic acid, aldonic acids, sugar dicarboxylic acids, formic acid, oxalic acid and α-amino acids. The titration of the carbon dioxide formed can be done with 0.1 or 0.01 N solutions. The interference of atmospheric carbon dioxide is avoided by the use of pentane as a sealing liquid.     

Resolution of complex wax ester mixtures by glass capillary GC

A glass capillary GC method providing high resolution analysis of complex wax ester mixtures is described. The two key parameters needed for evaluating a wax ester mixture for industrial utility – the total carbon chain length and the number of carbon-carbon double bonds present in each component – are simply and rapidly obtained by this method.     

Short and practical synthesis of O-(p-biphenoyl)-N-tosyl-allo-threonine-derived oxazaborolidinone catalyst

O-(p-Biphenoyl)-N-tosyl-(L)-allo-threonine methyl ester is synthesized in three steps (65% overall yield) starting from commercially available (L)-allo-threonine methyl ester hydrochloride by N-acylation followed by N,O-acyl migration with inversion of the beta carbinol carbon and N-tosylation. Treatment of the methyl ester with dibromophenylborane gives oxazaborolidinone 1, which can be used as a Lewis acid catalyst for the asymmetric Michael and Diels-Alder reactions.     

UV-light mediated decomposition of a polyester for enrichment and release of semiconducting carbon nanotubes

Purification of single-walled carbon nanotubes using conjugated polymers to selectively disperse either semiconducting or metallic nanotubes is effective and has received significant attention. However, the interaction between the conjugated polymer and the nanotube surface is very strong, making it difficult to remove the adsorbed polymer. Here, we report a poly(carbazole-co-terephthalate) polymer that is not only selective for semiconducting carbon nanotubes but can also be largely removed from the nanotube surface via irradiation with UV light. Irradiation of the polymer-nanotube dispersion causes degradation of ester linkages in the polymer backbone, effectively cutting the polymer into fragments that no longer bind strongly to the nanotube surface. Characterization of the electronic nature of the samples was carried out via the combination of absorption, Raman, and fluorescence spectroscopy. In addition, thermogravimetric analysis allowed determination of the amount of polymer left on the nanotube surface after irradiation and indicated that a large proportion of the polymer is removed. The reported methodology opens new possibilities for purification of semiconducting single-walled carbon nanotubes and their isolation from the polymeric dispersant.     

Strategic Utilization of Multifunctional Carbene for Direct Synthesis of Carboxylic–Phosphinic Mixed Anhydride from CO2

Direct synthesis of carboxylic–phosphinic mixed anhydrides has been achieved by treating carbon dioxide with N‐phosphine oxide‐substituted imidazolylidenes (PoxIms) that contain both nucleophilic carbene and electrophilic phosphorus moieties. This novel mixed anhydride was efficiently derivatized into an ester, an amide, and an unsymmetrical ketone via transformation into its corresponding imidazolium salt followed by a dual substitution reaction. The presented work used well‐designed multifunctional carbene reagents to establish a novel utility for carbon dioxide in organic synthesis.     

Construction of vicinal quaternary carbon atoms by Ireland ester Claisen rearrangement: total synthesis of (±)-herbertenolide, (±)-herberteneacetal, (±)-herbertene-1,14-diol and (±)-herbertene-1,15-diol

Efficient total syntheses of the herbertane sesquiterpene title compounds have been accomplished employing an Ireland ester Claisen rearrangement and ring-closing metathesis reaction sequence based strategy for the construction of two stereogenic vicinal quaternary carbon atoms on a cyclopentane.     

K_2CO_3活化糖蜜基多孔炭的制备及双电层储能性能

以生物质糖蜜为原料,K_2CO_3为活化剂制备了糖蜜基多孔炭.K_2CO_3的使用改善了传统活化剂KOH对设备腐蚀的问题,避免了传统活化剂ZnCl_2可能引发的致毒性.分析了活化条件对产率的影响.采用扫描电子显微镜(SEM)、X射线衍射(XRD)、N_2吸附-脱附分析(BET)和傅里叶变换红外光谱(FTIR)表征了糖蜜基多孔炭,结果表明其为石墨化层堆结构,表面富含羟基、羧基、酯基或醚基等官能团,具有丰富的孔结构,比表面积可达1219 m~2/g,并证实了800℃为最佳的活化温度.电化学测试结果表明,糖蜜基多孔炭具有优良的双电层储能性能.     

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。     

基于从头计算法的三维碳同素异形体结构设计

由于独特的成键特性,在不同温度和压强下,碳具有丰富的结构特性。除了实验上已发现各种同素异形体,理论计算也预言了丰富的新结构。在本文中,我们对第一性原理计算预言的三维碳同素异形体做了综述,特别地,我们着重关注了泡沫状的碳结构。碳泡沫主要由石墨片断以各种碳键连接而成,具体多孔结构及较大的表面积。另外,针对由低维碳结构,如碳富勒烯、纳米芽、纳米管及石墨烯等组成的三维碳超结构以及其他三维碳晶体我们也做了概述。这些新型碳结构有的由混杂的sp-sp²碳或者纯sp²碳组成(H-6, bct-4, C-20, K₄等),有的质量密度比金刚石还大(C₈, hP3, tl12, tp12等),有的可以由石墨在室温高压下转化而成(M碳, bct-4碳, W碳, Z碳等)。在这些预言的碳同素异形体中,有些在将来可能在实验室合成。     

Micro-Raman and Tip-Enhanced Raman Spectroscopy of Carbon Allotropes

Summary: Raman spectroscopic data are obtained on various carbon allotropes like diamond, amorphous carbon, graphite, graphene and single wall carbon nanotubes by micro-Raman spectroscopy, tip-enhanced Raman spectroscopy and tip-enhanced Raman spectroscopy imaging, and the potentials of these techniques for advanced analysis of carbon structures are discussed. Depending on the local organisation of carbon the characteristic Raman bands can be found at different wavenumber positions, and e.g. quality or dimensions of structures of the samples quantitatively can be calculated. In particular tip-enhanced Raman spectroscopy allows the investigation of individual single wall carbon nanotubes and graphene sheets and imaging of e.g. local defects with nanometer lateral resolution. Raman spectra of all carbon allotropes are presented and discussed.     

Reactivity and Coaggregation of p-Nitrophenyl Esters with Polymer Micelles at Solid Surfaces

The polymer micelle, poly[(N-(n-dodecyl)-4-vinylpyridiniumco-N-ethyl-4-vinylpyridinium) bromide], PDE, containing 30% dodecyl groups has been found to promote the adhesion of lipophiles to various surfaces including quartz, polystyrene, and poly(methyl methacrylate) cuvette surfaces from aqueous solutions. The adsorption of PDE/ester coaggregates to the surfaces was studied by hydrolysis of p-nitrophenyl esters in aqueous PDE(30) solutions. The extent of reaction of p-nitrophenyl myristate, an ester with a linear acyl carbon chain length of 14, can be viewed as a probe to study the adhesion of the PDE/ester coaggregates to the cuvette surfaces. The difference between initial concentration of ester and concentration of hydrolysis product, p-nitrophenoxide ion, gives the concentration of unreacted ester in the aggregates or film adhering to the solid surface. Up to 40% of p-nitrophenyl myristate was found unreacted on the surface of quartz cuvettes after apparent completion of the reaction. No adhesion of the related caproate ester with a linear acyl carbon chain length of 6 was detected. Copyright 2000 Academic Press.     

碳纳米管的羟甲基化及其马来酸酐接枝研究

利用甲醛的亲电性能, 对化学气相沉积法(CVD)制备的多壁碳纳米管(MWCNTs)进行羟甲基化, 并在此基础上酯化接枝马来酸酐, 运用透射电子显微镜(TEM)、红外光谱和Zeta电位仪表征了改性后的MWCNTs的表面结构. TEM结果显示, 酯化后的MWCNTs明显增粗, 说明表面已附有物质. 红外结果表明, 羟甲基后的MWCNTs的表面有了羟基和亚甲基, 而马来酸酐酯化接枝后的MWCNTs有亚甲基和酯基官能团. 光学图像分析表明, 经甲醛处理后的MWCNTs在水溶液中的分散性明显提高, 而马来酸酐酯化接枝后的MWCNTs在二甲苯中的分散性明显增强. Zeta电位的测试结果表明, 甲醛处理过的MWCNTs颗粒在水中, 负电荷增多, 增强了其在悬浮液在溶液中的稳定性.     

The Role of Functional Moieties on Carbon Nanotube Surfaces in Solar Energy Conversion

An easily dispersible multiwalled carbon nanotube (MWCNT) derivative is prepared, and provides a platform for the synthesis of the phenyl butyric acid methyl ester (PCBM) analog. The carbene addition reaction of MWCNTs makes derivatives that are less soluble in organic solvents; by exploiting this differential solubility, PCBM analogs can be separated from the unreacted functionalized MWCNTs. Our experimental evidences indicate that it is the unique properties of the butyric acid methyl ester moiety that makes the acceptor material perform better in organic photovoltaics (OPVs). Studying the combination of the butyric acid methyl ester moiety and the deagglomerated functionalized MWCNT structures provides us an insight into nanoscale charge transfer and transportation inside the donor–acceptor domain. It is demonstrated that a strong structure–property relationship exists for the functionalized MWCNTs, which enables us to correlate the functionality on the carbon nanostructures with performance in OPVs.