Effects of Citric Acid Concentration and Activation Temperature on the Synthesis of Carbon Nanotubes

A series of Ni-La-Mg catalyst samples were prepared by citric acid complex method, and carbonnanotubes were synthesized by catalytic decomposition of CH4 on these catalysts. The effects of the citricacid concentration and the activation temperature on catalytic activity were investigated by CO adsorption,TEM and XRD techniques. The experimental results showed that the particle size of the catalysts preparedthrough gel auto-combustion varied with the concentration of citric acid. Therefore carbon nanotubes with different diameters were obtained correspondingly. The effect of activation temperature on the activity of catalyst was negligible from 500 to 700℃, but it became pronounced at lower or higher temperatures.     

Intrinsic Kinetics of Dimethyl Ether Synthesis from Syngas

The intrinsic kinetics of dimethyl ether (DME) synthesis from syngas over a methanol synthesis catalyst mixed with methanol dehydration catalyst has been investigated in a tubular integral reactor at 3-7MPa and 220-260℃. The three reactions including methanol synthesis from CO and H2, CO2 and H2, and methanol dehydration were chosen as the independent reactions. The L-H kinetic model was presented for dimethyl ether synthesis and the parameters of the model were obtained by using simplex method combined with genetic algorithm. The model is reliable according to statistical analysis and residual error analysis. The synergy effect of the reactions over the bifunctional catalyst was compared with the effect for methanol synthesis catalyst under the same conditions based on the model. The effects of syngas containing N2 on the reactions were also simulated.     

First Synthesis of a Series of New Natural Glucosides

Alkyl glucoside 1 and aryl glycosides 2-4 were highly stereospecifically synthesized over 4-6 steps from commercially available starting materials. The coupling reaction of the acetobromo-α-D-glucose with the unprotective dihydroxy aglycon in the presence of silver oxide, or with aromatic aglycon in the presence of sodium hydroxide produced the key intermediate. Only β-configuration glycosides were formed in this procedure. The synthesis of all these glycosides was reported for the first time.     

Effect of pH on the Hydrothermal Synthesis of BN Nanocrystals

Boron nitride (BN) has been synthesized using hydrothermal synthesis method. The experimental results showed that the pH value of the reaction solution has an important effect on the yield and phases of BN samples. As the pH value decreased, the content of cBN increased and the yield improved. The increase in cBN content is resulted from the conversion of oBN into cBN under hydrothermal condition, and the growth of cBN nanocrystals may due to the decrease in the reaction speed, thus the crystalline perfection of BN improved when the pH value decreased.     

Protease-catalyzed Synthesis of Bz-Arg-Gly-Asp-OMe in Full Aqueous Medium

Synthesis of N-benzoyl-argininylglycylasparagine methyl ester(Bz-Arg-Gly-Asp-OMe),a precursor tripeptide of Arg-Gly-Asp)was catalyzed by papain under kinetic control,at alkaline pH,in a full aqueous medium.The substrates were N-benzoyl-argininylglycine ethyl ester and asparagine dimethyl ester.An aqueous solution of 0.1 mol/L KCl/NaOH containing 8 mmol/L EDTA and 2 mmol/L DTT was selected as the reaction medium.The synthesized hydrophilic tripeptide was soluble in the reaction medium during the reaction process,however,the secondary hydro-lysis of the tripeptide product was not considerable.The effects of different factors,including water content,temperature,reaction time,and molar ratio of the substrates,on the yield of Bz-Arg-Gly-Asp-OMe were examined.The optimal reaction conditions were 0.05 mol/L Bz-Arg-Gly-OEt and 0.15 mol/L Asp(-OMe)2·HCl in 0.1 mol/L KCl/NaOH solution(pH 8.5),at 40 ℃,and a reaction time of 60 min,with a maximum conversion yield of 62.4%.     

Preliminary Synthesis and Characterization of Mesoporous Nanocrystalline Zirconia

A novel method to prepare mesoporous nano-zirconia was developed. The synthesis was carried out in the presence of PEO surfactants via a solid-state reaction. The materials exhibit a strong diffraction peak at low 28 angle and their nitrogen adsorption/desorption isotherms are typical of type IV with H1 hysteresis loops. The pore structure imaged by TEM can be described as wormhole domains. The tetragonal zirconia nanocrystals are uniform in size (around 1.5 nm) and their mesopores focus on around 4.6 nm. The zirconia nanocrystal growth is tentatively postulated to be the result of an aggregation mechanism. This study also reveals that the PEO surfactants can interact with the Zr-O-Zr framework to reinforce the thermal stability of zirconia. The ratio of NaOH to ZrOC12, crystallization and calcination temperature play an important role in the synthesis of mesoporous nano-zirconia.     

Synthesis of Novel Bisoxazoline Ligands for the Enantioselective Diels-Alder Reaction

The Diels-Alder reaction is the most useful method for six-membered ring formation1. As a consequence, a number of effective enantioselective processes have been developed over the years 2-4. Of particular interest, metal bisoxazoline complexes formed fro…     

Synthesis and Photochromic Properties of the Derivatives of Spiropyrans Containing a Mesogenic Group

The photochromic compounds continue to attract significant attention in view of their general applicability as optical information storage materials or switching devices1-2.In order to develop novel bifunctional and multifunctional materials,special attention has been paid to photochromic liquid crystalline compounds.Many studies have been carried out for all kinds of mixed systems,which are to dope small amounts photochromic compounds into liquid crystal3-4.However,the combination of the prop…     

Kinetic Rates of the Fischer Tropsch Synthesis on a Co/Nb2O5 Catalyst

The kinetics of the Fischer-Tropsch reaction over a Co/Nb2O5 catalyst in a fixed bed reactor was investigated experimentally. Experiments were carried out under isothermal and isobaric conditions (T=543 K, P=2.1 MPa) and under different conditions of several H2/CO feed molar ratio (0.49-4.79), space velocities (0.2-3.8 h-1), mass of catalyst (0.3-1.5 g), and CO conversion (10%-29%). Synthesis gas conversion was measured and data were reduced to estimate the kinetic parameters for different Langmuir-Hinshelwood rate expressions. Differential and integral reactor models were used for the nonlinear regression of kinetics parameters. One of the rate equations could well explain the data. The hydrocarbon product distributions that were experimentally determined exhibited an unusual behavior, and a possible explanation was discussed.     

Synthesis, Structural Characterization of Ferrocenyl Iminophosphines and Amidophosphines as Well as Their Application in the Suzuki Reaction

Ferrocenyliminophosphine 1 and 1,1'-bisferrocenyliminophosphine 2 were easily prepared from the condensation of formylferrocene or 1,1'-diformylferrocene with 2-(diphenylphosphino)aniline.The following reduction of imine group by LiAlH4 led to the formation of the corresponding ferrocenyl amidophosphines 3 and 4.The new ligands 2-4 were well characterized by IR,1H NMR,31P NMR spectra,elemental analysis,and ESI-MS.The catalytic activity of all the ligands with palladium compounds in the Suzuki reaction was evaluated.Ligand 1,in combination with Pd(OAc)2,was found to be the most effective for the Suzuki reaction of aryl bromides with phenylboronic acid.Typically,the use of 0.1%(molar fraction)of Pd(OAc)2/ligand 1 in the presence of two equivalents of K2CO3 as base in toluene at 110 ℃ provided good to excellent yields of the coupled products.     

Synthesis of the First

A "true" allenophane with several rings and allenic bridges was synthesized. The key step in the preparation of 1 was the cyclization to a 28-membered macrocycle (52 % yield) starting from a linear molecule, which already contains three of the four allene units.     

Total Synthesis of Siomycin A: Completion of the Total Synthesis

The total synthesis of siomycin A ( 1 ), a representative compound of the thiostrepton family of peptide antibiotics, was achieved by incorporating the five synthetic segments A ( 2 ), B ( 3 ), C ( 4 ), D ( 5 ), and E ( 6 ). The dehydropiperidine segment A ( 2 ) was esterified with the dihydroquinoline segment C ( 4 ), and the subsequent coupling with the β‐phenylselenoalanine dipeptide segment D ( 5 ) at the segment C portion followed by lactamization between the segments A and D gave segment A‐C‐D ( 27 ). This was amidated with the pentapeptide segment B ( 3 ) at the segment A portion followed by one‐pot cyclization (between segments A and B) and elongation (with the β‐phenylselenoalanine dipeptide segment E ( 6 ) at the segment A portion), thus furnishing siomycin A ( 1 ).     

First Synthesis of Cotarnone,the Key Intermediate for the Synthesis of Cotarnine

The first synthesis of cotarnone (2), a degradation product of cotarnine (1), was achieved from 2-hydroxy-3-methoxy-benzaldehyde (o-vanillin), and 2 can be converted to 1 by a known method.     

费-托合成制液态烃研究进展

天然气先转化为合成气, 再经F ischer-Trop sch 反应合成液体烃类(GTL ) 是近年来天然气转化利用研究的主流。Shell、Sasol、Exxon、Syntroleum 等公司都分别开发了各自的GTL 专利技术。GTL 产品中液体燃料基本上由直链烷、烯烃组成, 具有无硫、无氮、无金属、无芳烃等特点, 是对环境友好的燃料油和化学品。由于合成气生成技术、F-T 合成催化剂和反应工艺的不断改进, 用GTL 技术开发利用边远地区和分散的中小气田的天然气资源在价格上已能和原油竞争。本文对F-T 合成催化剂、反应器及GTL 技术发展动态等方面做了综述, 讨论了其今后的发展趋势, 并指出在我国开展GTL 技术研究的必要性。     

芳氨基硫脲类化合物的合成

报道了用固-液相转移催化法制得烃基异硫氰酸酯, 不经分离直接与溴代邻肼基苯甲酸作用, 合成11种新的芳氨基硫脲类化合物。讨论了生成烃基异硫氰酸酯的可能机理。     

Optimizing the Synthesis of Tetratellurafulvalene

A systematic synthetic study of the pi-donor tetratellurafulvalene (TTeF, 6) has resulted in an optimized preparation producing repeatable yields of over 20%. The use of a "one-step" Li/Sn metal exchange/Te(0) insertion procedure and freshly prepared microcrystalline Te(0) serve to drive toward products, the equilibria converting (Z)-1,2-bis(trimethylstannyl)ethylene (1) to its corresponding metal-exchanged vinyllithium species and subsequently to lithium ditellurolate 5. Furthermore, the use of LiCl as an additive to enhance the reactivity of n-BuLi in these metal exchange reactions also increases yields and reproducibility. The slow addition of 1 equiv of tetrahaloethylene during the final cyclization step favors intramolecular reactions which produce TTeF vs intermolecular reactions that lead to oligomeric byproducts. The use of tetrabromoethylene in place of tetrachloroethylene in this step also reduces byproduct formation.     

Synthesis of the himandrine skeleton

The hexacyclic himandrine skeleton 5, which is present in the most complex alkaloids of the tropical rain forest tree Galbulimima belgraveana, has been prepared for the first time. The synthesis begins from the known [3.2.1]benzobicyclooctene intermediate 10. Key steps include a Diels-Alder cycloaddition, Curtius rearrangement, Birch reduction, an intramolecular nucleophilic amination, and a palladium-mediated alkene amination. [reaction: see text]     

Total Synthesis of the Hamigerans

The first total synthesis of hamigerans D, G, L, and N–Q has been accomplished. A convergent approach was used to build the basic tricarbocyclic ring system bearing a 5‐6‐6 structure. A sequence of oxidative cleavage, homologation, and ring regeneration provided access to the 5‐7‐6 skeleton of hamigeran G. Based on the biogenetic hypothesis, elegant and highly efficient biomimetic transformations of hamigeran G into hamigerans D, N–Q, and L were achieved.     

Synthesis of the landomycinone skeleton

The synthesis of the highly functionalized tetracyclic skeleton of landomycinone (2), the aglycon of landomycins, was performed using two pivotal steps relying on metal-catalyzed reactions. They are (1) a [2 + 2 + 2] cycloaddition of alkynes promoted by Wilkinson's catalyst to build rings B and C concomitantly and (2) a ring-closing metathesis followed by aromatization to build ring D.     

Synthesis of the hexapeptides glycyl-L-valyl-L-seryl-L-prolyl-L-lysyl-L-leucine

Summary The synthesis of the methyl ester of the hexapeptide N-Cbo-glycyl-L-valyl-L-seryl-L-prolyl-N-tos-L-lysyl-L-leucine, not described in the literature, has been affected.T. G. Shevchenko Kiev State University. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 41–43, January–February, 1975.