α—氨基磷酸酯与N—氯乙酰基甘氨酸乙酯反应机理的研究

用MMX分子力学程序公及分子图形学方法对α-氨基磷酸酯与N－氯乙酰基甘氨酸乙酯反应机理进行了探讨，结果表明，此类反应热力学因素不起主要作用，动力学因素起主要作用，取代基突效应是影响反应历程的重要因素。     

氮氧自由基研究（ⅩⅩⅢ）——哌啶氮氧自由基及其氧铵盐与N，N，N′，N′—

ESR波谱和流动－停止UV动力学研究表明，水溶液中2，2，6，6－四甲基－4－羟基哌啶－1－氧自由基1和相应氧铵溴盐2均可将N，N，N′，N′－四甲基对苯二胺（TMPD）氧化为相应自由基正离子TMPD^＋，2还能将TMPD^＋进一步氧化为二价正离子TMPD^2＋。TMPD^＋可发生可逆歧化，其稳定性强烈受介质酸碱性的影响，利用计算机对动力学曲线的模拟测得上述有关反应的速率常数，并讨论了反应机理。     

N,N-二甲基羟基胺与V(Ⅴ)氧化还原反应动力学及机理研究

二甲基羟胺;反应机理;N;N-二甲基羟基胺与V(Ⅴ)氧化还原反应动力学及机理研究     

8-二甲基-7-甲氧基-5-烯-壬腈氧化物环加成反应机理

用过渡态理论和AM1方法，对8－二甲基－7－甲氧基－5－烯－壬腈氧化物分子内环加成反应机理进行了研究。结果表明，存在两种产物的平行反应，对两个反应的速率常数比值的计算，得到反式和顺式的产率比为90.5:9.5，与实验产率比值（≥85：15）结果接近。标题物立体专一选择性由活化焓和活化熵共同决定。     

N,N-二甲基苄胺催化合成丙烯酸间苯二酚环氧酯的机理

Ｎ，Ｎ－二甲基苄胺催化合成丙烯酸间苯二酚环氧酯的机理高俊刚，王洪芳，袁翠红（河北大学化学系，保定０７１００２）关键词丙烯酸间苯二酚环氧酯，Ｎ，Ｎ－二甲基苄胺，催化反应机理不饱和酸环氧酯是由不饱和核酸与环氧化合物进行环氧化反应形成的一种化合物，它在涂料...     

N,N-二甲基乙醇胺三个季铵盐衍生物的合成与表征

以N，N－二甲基甲酰胺为溶剂，乙酸乙酯为催化剂，N，N－二甲基乙醇胺分别与苄基氯、十二烷基溴和十八烷基溴作用，得到了3个N，N－二甲基乙醇胺的季铵盐衍生物。标题化合物结构经IR，^1H NMR,^13C NMRt FAB-MS表征。     

纳米晶镁铝水滑石的制备及其热分解机理

研究了无机阻燃剂镁铝水滑石纳米晶的制备及其热分解机理.采用常压下,一步反应的液相法制备镁铝水滑石试样，用XRD和TEM测试试样的相组成和形貌，针状镁铝水滑石纳米晶体的长度约80 nm.依据DSC和DTA-TG测试结果，发现镁铝水滑石纳米晶的热分解由两个阶段组成:第一个吸热峰出现在220 ℃左右，第二个吸热峰出现在380 ℃左右.研究了反应时间对所得镁铝水滑石试样的热分解性能的影响，发现延长反应时间，镁铝水滑石试样的第一次、第二次热分解的起始温度升高,第一次热分解的失重值增大，最后剩余氧化物的量增大，从而增强镁铝水滑石阻燃剂的阻燃性能.根据不同升温速率下获得的DSC测试数据，应用Achar微分法、Šatava-Šesták积分法和Ozawa积分法对镁铝水滑石纳米晶热分解的第二个阶段进行了动力学计算和分析，确定该段的热分解机理函数积分式为(1－α)－1－1.     

气相中H2O2与N2O反应机理的探讨

采用RHF/AM1方法研究了H2O2与N2O的反应机理.计算结果表明,该反应是多步反应,先后通过2个过渡态（TS1,TS3）,1个内旋转位垒（TS2）,2个中间体（IM1,IM2）.其中从反应物Re到TS1为整个反应的决速步骤,速控步骤的活化能为323.04 kJ•mol－1.整个反应为一放热反应,放出的热量为147.67kJ•mol－1.     

N2O分解反应的动力学-Monte Carlo模拟

N2O是一种大气污染物，许多金属氧化物能使它发生分解反应，生成N2和O2．因此，N2O的催化分解反应很早就引起了研究者的兴趣[1]．传统的动力学着重去研究反应速率和一些反应参数，如温度、压力、组成等的关系，往往忽视催化表面的性质，从而使速率方程变得十分复杂．Kobayashi等人利用过渡应答法研究了N2O分解反应的动力学，计算了两个基元步骤的速率常数，但没有给出表面物种浓度变化的更进一步的信息[2]．近年来，MonteCarlo方法在研究表面反应机理和动力学方面已经取得了一些成功[3，4]．我们曾用MonteCarlo方法研究了N2O催化分解…     

新型多取代2，7—萘二酸二乙酯的合成

以4，6－二甲基－2－甲氧基－1，3－苯二甲酸二乙酯为原料，经Micheal加成、环化、溴化、消除等5步反应，合成新型的多取代2，7－萘二甲酸二乙酯。该合成路线步骤少，收率高，反应条件温和、产物中的4个新化合物的结构均经元素分析、核磁共振、红外光谱和质谱确证。     

Gas chromatographic assay for N,N-dimethylglycine in urine.

A gas chromatographic method for the determination of N,N-dimethylglycine in urine has been developed. After clean-up by cation-exchange, N,N-dimethylglycine was derivatized with ethanol and hydrochloric acid to form the corresponding ethyl ester. After evaporation of solvent, N,N-dimethylglycine ethyl ester was extracted into methylene chloride and chromatographed on a gas chromatograph equipped with a packed column containing 10% Carbowax 20 M. The detection limit of the method is 0.01 mM N,N-dimethylglycine in urine. This method has been used to detect N,N-dimethylglycine in urine from healthy subjects as well as in urine from patients with metabolic disorders. These findings were verified by gas chromatography-mass spectrometry.     

量子化学研究NO在铜负载金红石表面降解反应

应用密度泛函方法结合嵌入簇模型对NO在铜负载金红石表面的吸附与降解进行了研究，计算结果表明NO分子解离以氧端吸附形成N₂O中间体然后解离N₂和 O₂.过程，另一条途径为NO双分子直接解离。通过能量学计算揭示了生成N₂O中间体对降解NO更为有利。     

苯丙氨酸光学异构体的酶法拆分

氨基酰化酶;苯丙氨酸光学异构体的酶法拆分     

A study on thermal oxidation mechanism of styrene-butadiene-styrene block copolymer (SBS)

The thermal oxidation process of SBS was studied by in situ FTIR and programming heating up DSC. The thermal oxidation mechanism of SBS was analyzed according to the activation energy and pre-exponential factor calculated by Friedman method. The results show that the oxidation of SBS is mainly on butadiene blocks. It is a self-catalyzed reaction containing four steps. The first step is the initiation of chain by free radical. The second is the growth and decomposition of polymer chain. The third is the formation of anhydride coming from dehydrated carbonyl. The fourth is the annihilation of active centers. Antioxidant which provides H atom easily can annihilate active free radical to protect SBS from thermal oxidation at lower temperature.     

Insights into the mechanism of BN generation via boron triazide precursor: theoretical study

Potential-energy surfaces for unimolecular decomposition of B(N3)(3) have been studied to understand the possible mechanism for BN generation. The decomposition of B(N3)(3) takes place on either the singlet and triplet surface, and both processes are high exothermic and obey sequential mechanisms. For the singlet reaction, the rate-determining step corresponds to cleavage of the first azide bond and linear (1)NBNN instead of (1)BN was suggested as the dominant product at room temperature. For the triplet surface, a fragment process from (3)BN(7) to (3)BN(5) is predicted to be the rate-determining step; once this barrier is counteracted, the subsequent decomposition processes could easily occur to form final product (3)BN. In addition, the possible mechanism for generating BN film via B(N3)(3) was discussed based on MC-SCF calculation results. These findings might be helpful in understanding the controllable decomposition of B(N3)(3) as well as its application in generating BN films.     

Theoretical evidence that Cu(I) complexation promotes degradation of S-nitrosothiols

The degradation of S-nitrosothiols (RSNOs) to release NO is believed to be catalyzed by CuI ions, but the mechanism remains unclear. Kinetic experiments have shown that decomposition rates vary significantly with the chemical nature of the RSNO considered. On the basis of first-principles calculations, the catalytic role of CuI ion is investigated for the decomposition of S-nitrosocysteine and its N-acetylated and ethyl ester derivatives, and for S-nitrosohomocysteine. This preliminary study focuses on the CuI-RSNO intermediates involved in the decomposition pathway. The model chemistry has been validated by comparing calculated CuI-ligand binding energies and S-N bond homolysis energies with available experimental data. Calculations show that the formation of CuI-RSNO intermediates results in weakening of the S-N bond and strengthening of the N-O bond, which would promote S-N bond breaking and NO release from S-nitrosothiols.     

N,N-dimethyl-beta-alanine as an inexpensive and efficient ligand for palladium-catalyzed Heck reaction

N,N-Dimethyl-beta-alanine was found to be a more powerful phosphine-free ligand than the previously reported ligand, N,N-dimethylglycine, in the Pd-catalyzed Heck reaction for a variety of aryl bromides, aryl iodides, and activated aryl chlorides with a practical turnover number of 10(3). Both kinetic and theoretical studies suggested that N,N-dimethyl-beta-alanine led to faster oxidative addition of an aryl halide to Pd than N,N-dimethylglycine. [reaction: see text]     

Unique role of water content in enzymatic synthesis of ethyl lactate using ionic liquid as solvent

Enzymatic synthesis of ethyl lactate was studied in organic solvents and in ionic liquids to determine optimal media for the reaction, and to investigate the effect of water content on the ester yield. Experiments proved that Cyphos 202 ionic liquid is the best solvent affording the highest ethyl lactate yields. Furthermore, 20 times less enzyme sufficed to carry out the reaction in this ionic liquid compared to organic solvents; ionic liquid could be applied as solvent. Using water removal, the ester yield decreased since a side reaction, dimerization of lactic acid, occurred as well. In contrast to these results, without water removal, the produced water was partly consumed by the decomposition of lactoyllactic acid to free lactic acid, increasing thus the substrate concentration of the mixture and enhancing the ester yield.     

Determination of carnitine by high-performance liquid chromatography using 9-anthryldiazomethane

The high-performance liquid chromatographic determination of carnitine chloride was investigated by using 9-anthryldiazomethane (ADAM) as a pre-column derivatization reagent. Carnitine chloride and the internal standard N,N-dimethylglycine reacted with ADAM to give a stable ester derivative in the presence of sodium dodecyl sulphate (SDS) used to mask the basic function. The ADAM derivative of carnitine was separated from decomposition products of the reagent and related compounds such as amino acid derivatives on a silica gel column eluted with methanol-5% aqueous SDS-phosphoric acid (990:10:1). The calibration plot was linear over a sample concentration range from 0.02 to 100 ng per injection. The detection limit for carnitine chloride was about 1 pg per injection (signal to noise ratio = 4), by fluorometric detection.     

Cellulose Derivatives Synthesized via Isocyanate and Activated Ester Pathways in Homogeneous Solutions of Lithium Chloride/N,N-Dimethylacetamide

Abstract

Cellulose carbamate and ester derivatives were synthesized in homogeneous solutions of lithium chloride (LiCl)/N,N-dimemyl-acetamide (DMAc) by the reaction of cellulose with ethyl 4-isocyanatobenzoate and the activated esters of N,N-dimethyl-aminobenzoic acids. Comparative reactions were performed with phenyl isocyanate and the activated ester of benzoic acid. All reactions were followed spectroscopically by FTIR, ¹H NMR, and ¹³C NMR. Degrees of substitution were calculated utilizing UV spectroscopy. The isocyanate reactions are facile allowing controllable degrees of substitution and high yields. By contrast, the activated ester pathway inherently results in lower degrees of substitution and lower yields due in part to undesirable side reactions.