二氧化硅负载的不同碱金属硝酸盐催化乳酸缩合反应制备2, 3-戊二酮的催化性能比较研究

考察了二氧化硅负载的不同碱金属硝酸盐催化乳酸缩合制备2, 3-戊二酮的催化性能。在考察的碱金属硝酸盐如硝酸锂、硝酸钠、硝酸钾和硝酸铯作为催化剂的前驱体中,重点关注的是碱金属阳离子对乳酸缩合反应的影响。通过对这些硝酸盐前驱体在反应中的作用研究,发现硝酸铯的催化性能最佳。为了探究影响催化剂性能的原因,对新鲜催化剂和用过的催化剂采用X射线衍射（XRD）、傅里叶变换红外（FT-IR）光谱进行表征,发现所有的硝酸盐在反应过程中快速地转变为乳酸盐,并认为乳酸盐才是催化活性物种。随后,又借助CO₂程序升温脱附（CO₂-TPD）表征手段对用过的催化剂的碱性进行表征,发现二氧化硅负载的硝酸铯具有最强的碱性。乳酸缩合反应制备2, 3-戊二酮被广泛认为是碱催化反应,因此,二氧化硅负载的硝酸铯展示了最佳的催化性能。此外,本文还讨论了反应温度、硝酸盐的负载量等工艺条件对反应的影响。以4.4%（x,摩尔分数）CsNO₃/SiO₂为催化剂,在反应温度为300 ℃条件下,2, 3-戊二酮的收率达54.1%。     

有机含能二硝酸盐的研究进展

综述了乙二胺二硝酸盐、偶氮二甲醚二硝酸盐、碳酰肼二硝酸盐、氨基胍类二硝酸盐和四嗪类二硝酸盐等有机含能二硝酸盐的主要合成方法及应用前景。     

稀土硝酸盐与1,2-环己基-12-冠-4配合物的合成与性质研究

近年来,虽然对冠醚12-冠-4与稀土硝酸盐配合物的研究已有一些工作,但对单环1,2-环已基-12-冠-4与稀土硝酸盐的配合物的研究,仍未见报道。本文报道稀土硝酸盐与单环己基-12-冠-4配合物的合成和性质研究。 1 实验部分 1.1 试剂与仪器 RE(NO_3)_3-xH_2O(x=3～5)的制备是将纯度99.9％的RE_2O_3溶于浓硝酸(A.R.)中,微热浓缩成糊状,冷至室温。置于盛有P_2O_5的保干器中备用。单环1,2-环已基-12-冠-4系上海试剂一厂产品。其余试剂均为分析纯,并在使用前经过进一步纯化及干燥处理。所     

荧光探针8-(3’,4’-二氨基苯)-二氟化硼-二吡咯甲烷用于光度法 灵敏测定食品中亚硝酸根和硝酸根

新型荧光探针8-(3’,4’-二氨基苯)-二氟化硼-二吡咯甲烷本体荧光很弱, 在酸性条件下, 和亚硝酸盐于30 ℃下反应15min后生成强荧光的三氮唑产物. 硝酸根可通过锌粉和氯化镉还原成亚硝酸根. 由此建立了一种新的荧光光谱法灵敏测定食品中的亚硝酸根和硝酸根. 其线性范围为0.06～6 μmol•L－1. 当信噪比等于3时, 方法的检出限为2 nmol• L－1. 将该方法首次用于多种食品中亚硝酸盐和硝酸盐的测定, 加标回收率为98.16%～103.20%.     

E-、Z-2＇-(1-咪唑基)-O-(α-甲基-二氯苄基)-2,4-二氯苯乙酮肟硝酸盐的合成与抑菌活性

E-、Z-2＇-(1-咪唑基)-O-(α-甲基-二氯苄基)-2;4-二氯苯乙酮肟硝酸盐的合成与抑菌活性     

2,5-二甲基-3,4-二乙酰基-1-芳基吡咯的合成

多取代吡咯;二乙酰基己二酮;取代苯胺;2;5-二甲基-3;4-二乙酰基-1-芳基吡咯的合成     

2-取代-5,5-二硝基嘧啶-4,6-二酮的合成和反应

研究了2-取代嘧啶-4,6-二酮的硝化反应, 产物为2-取代-5,5-二硝基嘧啶-4,6-二酮(3), 收率＞80%, 3与亲核试剂反应形成开环产物. 2-位取代基为烷基时, 嘧啶环5-位和侧链的α-位都发生反应, 当取代基为甲基时, 硝化产物为2-(二硝基亚甲基)-5,5-二硝基嘧啶-4,6-二酮(1), 1的水解产物为1,1-二氨基-2,2-硝基乙烯 (FOX-7) 和二硝基甲烷(2). 2-位取代基为羟基时, 硝化产物为5,5-二硝基巴比妥酸(7b), 7b水解可制得偕二硝基乙酰基脲(9b), 9b与KOH作用生成偕二硝基乙酰基脲钾盐(10b)和二硝基甲烷钾盐(11). 2-位取代基为氨基时, 硝化开环生成偕二硝基乙酰基胍(9a), 9a与KOH作用生成偕二硝基乙酰基胍钾盐(10a)和11. 当2-位无取代基时, 硝化产物无法分离, 结构推测为7c. 考察了亲核试剂对FOX-7收率的影响并对FOX-7的三种合成方法进行了评价, 对反应机理进行了探讨.     

叔丁基取代二苯并-18-冠-6的合成

以二甘醇和邻苯二酚为原料制得二苯并-18-冠-6;以多聚磷酸为催化剂和溶剂,将二苯并-18-冠-6与叔丁醇反应实现叔丁基化;利用正庚烷重结晶对叔丁基化反应产物进行纯化,得到4,4′-二叔丁基二苯并-18-冠-6和4,5′-二叔丁基二苯并-18-冠-6两种对称的二叔丁基二取代苯并冠醚产品.利用红外光谱和核磁共振谱表征了二叔丁基二取代苯并冠醚产物的结构。     

1,3-二叔丁基-5,5-二硝基嘧啶烷的合成及反应机理研究

1,3-二叔丁基-5,5-二硝基嘧啶烷(3)是混合炸药含能增塑剂1,3,5,5-四硝基-1,3-二氮杂环环己烷的关键硝化前体. 通过研究3的合成反应机理, 目的是为制备1,3,5,5-四硝基-1,3-二氮杂环环己烷的工艺优化提供理论依据. 以2,2-二硝基-1,3-丙二醇(1)、甲醛和叔丁胺为原料, 通过Mannich缩合反应得到1,3-二叔丁基-5,5-二硝基嘧啶烷. 采用同位素示踪技术以及分离关键中间体对反应机理进行推测. 以氘代甲醛、1和叔丁胺缩合得到氘标记的3, ¹H NMR和MS分析结果表明: 在反应过程中1首先解离生成偕二硝基甲烷和甲醛, 小分子碎片随机组合生成了3. 分离出了关键中间体1-叔丁氨基-2,2-二硝基乙烷. 根据所获得的证据, 推断了3的合成反应机理.     

二氨基二苯并-14-冠-4的合成与表征

二硝基二苯并冠醚;二氨基二苯并冠醚;二氨基二苯并-14-冠-4的合成与表征     

Sublimation properties of CoF(3): mass spectrometric and quantum chemical studies

The sublimation of cobalt trifluoride was studied using the Knudsen effusion method combined with mass spectrometry. The pressure of F was directly measured for decomposition of CoF(3)(s) into CoF(2)(s). The average kinetic energy of CoF(2)(+), CoF(+) and Co(+) fragment ions was determined and the relative ionisation cross section curves measured from 6 eV to 100 eV. Thermodynamic functions of gaseous CoF(3) and Co(2)F(6), were evaluated from geometrical and vibrational parameters provided from theoretical calculations. Heats of formation of CoF(3)(s), CoF(3)(g), Co(2)F(6)(g) were established as (-784 +/- 6) kJ/mol, (-565 +/- 11) kJ/mol and (-1289 +/- 22) kJ/mol, respectively.     

PANi电极在不同电解液中的电化学电容性能研究

应用化学氧化聚合法制备了超级电容器用聚苯胺电极材料.FTIR、SEM及电化学电容测试表明:聚苯胺由纳米颗粒堆积而成,颗粒大小50nm左右;在H2SO4、NaNO3或KOH电解液(浓度均为1mol/L)中,5mA/cm2电流密度下,PANi电极比电容分别为404F/g、208F/g和279F/g;如H2SO4浓度升高至2mol/L或6mol/L,比电容明显下降,仅为330F/g或248F/g.     

硫代乙酰胺-聚苯乙烯树脂吸附剂制备及其对铅、镉、铜、镍、铁的萃取

以大孔聚苯乙烯苄胺树脂为载体通过Mannich反应制备了一种新型固相萃取吸附剂TAA-PS(硫代乙酰胺改性聚苯乙烯树脂)。利用FTIR和元素分析对其进行表征。研究了其对痕量金属离子的萃取性能,确定了对Pb2 、Cd2 、Cu2 、Ni2 和Fe3 等金属离子的最佳吸附条件。与其它吸附剂相比,本研究合成的固相萃取吸附剂具有高吸附容量和相当快的吸附速率。应用于自来水和湖水中痕量Pb2 、Cd2 、Cu2 、Ni2 和Fe3 的萃取富集,取得较好结果。     

Polymer fractionation using chromatographic column packed with novel regenerated cellulose beads modified with silane

Novel microporous beads with the particle size of about 90 microm were prepared, for the first time, from cellulose and konjac glucomannan (RC/KGM3) in 1.5 M NaOH/0.65 M thiourea aqueous solution by emulsification method. The microporous beads were then modified with silane to avoid the adsorption of polymers containing hydroxyl groups, coded as RC/KGM3-Si. A preparative size-exclusion chromatographic (SEC) column (500 mm x 20 mm) was packed with RC/KGM3-Si, and its exclusion limit and fractionation range of the stationary phase were, respectively, weight-average molecular masses (Mw) of 4.8 x 10(5) g/mol and 5.3 x 10(3)-4.8 x 10(5) g/mol for polystyrene in tetrahydrofuran. The preparative SEC column was used to fractionate poly(epsilon-caprolactone) (PCL, Mw = 8.31 x 10(4) g/mol polydispersity index d= 1.55) in tetrahydrofuran and a polysaccharide PC3-2 (Mw = 1.21 x 10(5) g/mol, d= 1.70) in 0.05 M NaOH aqueous solution, respectively. The Mw values of the fractions determined by analytical SEC combined with laser light scattering were from 1.2 x 10(4) to 1.84 x 10(5) for PCL and from 8.5 x 10(4) to 2.13 x 10(5) for PC3-2, as well as d from 1.2 to 1.5. The results indicated that the preparative SEC has good fractionation efficiency in both organic solvent and alkaline aqueous solution for the various polymers.     

The aromaticity of pyracylene: an experimental and computational study of the energetics of the hydrogenation of acenaphthylene and pyracylene

In this work, the aromaticity of pyracylene (2) was investigated from an energetic point of view. The standard enthalpy of hydrogenation of acenaphthylene (1) to acenaphthene (3) at 298.15 K was determined to be minus sign(114.5 +/- 4.2) kJ x mol(-1) in toluene solution and minus sign(107.9 +/- 4.2) kJ x mol(-1) in the gas phase, by combining results of combustion and reaction-solution calorimetry. A direct calorimetric measurement of the standard enthalpy of hydrogenation of pyracylene (2) to pyracene (4) in toluene at 298.15 K gave -(249.9 plus minus 4.6) kJ x mol(-1). The corresponding enthalpy of hydrogenation in the gas phase, computed from the Delta(f)H(o)m(cr) and DeltaH(o)m(sub) values obtained in this work for 2 and 4, was -(236.0 +/- 7.0) kJ x mol(-1). Molecular mechanics calculations (MM3) led to Delta(hyd)H(o)m(1,g) = -110.9 kJ x mol(-1) and Delta(hyd)H(o)m(2,g) = -249.3 kJ x mol(-1) at 298.15 K. Density functional theory calculations [B3LYP/6-311+G(3d,2p)//B3LYP/6-31G(d)] provided Delta(hyd)H(o)m(2,g) = -(244.6 +/- 8.9) kJ x mol(-1) at 298.15 K. The results are put in perspective with discussions concerning the "aromaticity" of pyracylene. It is concluded that, on energetic grounds, pyracylene is a borderline case in terms of aromaticity/antiaromaticity character.     

Energetics of C-Cl, C-Br, and C-I bonds in haloacetic acids: enthalpies of formation of XCH2COOH (X=CI, Br, I) compounds and the carboxymethyl radical

The standard molar enthalpies of formation of chloro-, bromo-, and iodoacetic acids in the crystalline state, at 298.15 K, were determined as deltafH(o)m(C2H3O2Cl, cr alpha)=-(509.74+/- 0.49) kJ x mol(-1), deltafH(o)m(C2H3O2Br, cr I)-(466.98 +/- 1.08) kJ x mol(-1), and deltafH(o)m (C2H3O2I, cr)=-(415.44 +/- 1.53) kJ x mol(-1), respectively, by rotating-bomb combustion calorimetry. Vapor pressure versus temperature measurements by the Knudsen effusion method led to deltasubH(o)m(C2H3O2Cl)=(82.19 +/- 0.92) kJ x mol(-1), deltasubH(o)m(C2H3O2Br)=(83.50 +/- 2.95) kJ x mol(-1), and deltasubH(o)m-(C2H3O2I) = (86.47 +/- 1.02) kJ x mol(-1), at 298.15 K. From the obtained deltafH(o)m(cr) and deltasubH(o)m values it was possible to derive deltafH(o)m(C2H3O2Cl, g)=-(427.55 +/- 1.04) kJ x mol(-1), deltafH(o)m (C2H3O2Br, g)=-(383.48 +/- 3.14) kJ x mol(-1), and deltafH(o)m(C2H3O2I, g)=-(328.97 +/- 1.84) kJ x mol(-1). These data, taken with a published value of the enthalpy of formation of acetic acid, and the enthalpy of formation of the carboxymethyl radical, deltafH(o)m(CH2COOH, g)=-(238 +/- 2) kJ x mol(-1), obtained from density functional theory calculations, led to DHo(H-CH2COOH)=(412.8 +/- 3.2) kJ x mol(-1), DHo(Cl-CH2COOH)=(310.9 +/- 2.2) kJ x mol(-1), DHo(Br-CH2COOH)=(257.4 +/- 3.7) kJ x mol(-1), and DHo(I-CH2COOH)=(197.8 +/- 2.7) kJ x mol(-1). A discussion of the C-X bonding energetics in XCH2COOH, CH3X, C2H5X, C2H3X, and C6H5X (X=H, Cl, Br, I) compounds is presented.     

Energetics of hydroxybenzoic acids and of the corresponding carboxyphenoxyl radicals. Intramolecular hydrogen bonding in 2-hydroxybenzoic acid

The energetics of the phenolic O-H bond in the three hydroxybenzoic acid isomers and of the intramolecular hydrogen O-H- - -O-C bond in 2-hydroxybenzoic acid, 2-OHBA, were investigated by using a combination of experimental and theoretical methods. The standard molar enthalpies of formation of monoclinic 3- and 4-hydroxybenzoic acids, at 298.15 K, were determined as Delta(f)(3-OHBA, cr) = -593.9 +/- 2.0 kJ x mol(-1) and Delta(f)(4-OHBA, cr) = -597.2 +/- 1.4 kJ x mol(-1), by combustion calorimetry. Calvet drop-sublimation calorimetric measurements on monoclinic samples of 2-, 3-, and 4-OHBA, led to the following enthalpy of sublimation values at 298.15 K: Delta(sub)(2-OHBA) = 94.4 +/- 0.4 kJ x mol(-1), Delta(sub)(3-OHBA) = 118.3 +/- 1.1 kJ x mol(-1), and Delta(sub)(4-OHBA) = 117.0 +/- 0.5 kJ x mol(-1). From the obtained Delta(f)(cr) and Delta(sub) values and the previously reported enthalpy of formation of monoclinic 2-OHBA (-591.7 +/- 1.3 kJ x mol(-1)), it was possible to derive Delta(f)(2-OHBA, g) = -497.3 +/- 1.4 kJ x mol(-1), Delta(f)(3-OHBA, g) = -475.6 +/- 2.3 kJ x mol(-1), and Delta(f)(4-OHBA, cr) = -480.2 +/- 1.5 kJ x mol(-1). These values, together with the enthalpies of isodesmic and isogyric gas-phase reactions predicted by density functional theory (B3PW91/aug-cc-pVDZ, MPW1PW91/aug-cc-pVDZ, and MPW1PW91/aug-cc-pVTZ) and the CBS-QMPW1 methods, were used to derive the enthalpies of formation of the gaseous 2-, 3-, and 4-carboxyphenoxyl radicals as (2-HOOCC(6)H(4)O(*), g) = -322.5 +/- 3.0 kJ.mol(-1) Delta(f)(3-HOOCC(6)H(4)O(*), g) = -310.0 +/- 3.0 kJ x mol(-1), and Delta(f)(4-HOOCC(6)H(4)O(*), g) = -318.2 +/- 3.0 kJ x mol(-1). The O-H bond dissociation enthalpies in 2-OHBA, 3-OHBA, and 4-OHBA were 392.8 +/- 3.3, 383.6 +/- 3.8, and 380.0 +/- 3.4 kJ x mol(-1), respectively. Finally, by using the ortho-para method, it was found that the H- - -O intramolecular hydrogen bond in the 2-carboxyphenoxyl radical is 25.7 kJ x mol(-1), which is ca. 6-9 kJ x mol(-1) above the one estimated in its parent (2-OHBA), viz. 20.2 kJ x mol(-1) (theoretical) or 17.1 +/- 2.1 kJ x mol(-1) (experimental).     

Conformational energies for 2-substituted butanes

The conformational free energies for some 2-substituted butanes where X = F, Cl, CN, and CCH were calculated using G3-B3, CBS-QB3, and CCSD(T)/6-311++G(2d,p) as well as other theoretical levels. The above methods gave consistent results with free energies relative to the trans conformers as follows: X = CCH, g+ = 0.77 +/- 0.05 kcal/mol. g- = 0.88 +/- 0.05 kcal/mol; X = CN, g+ = 0.85 +/- 0.05 kcal/mol, g- = 0.75 +/- 0.05 kcal/mol; X = Cl, g+ = 0.70 +/- 0.05 kcal/ml, g- = 0.80 +/- 0.05 kcal/mol; and X = F, g+ = 0.53 +/- 0.05 kcal/mol, g- = 0.83 +/- 0.05 kcal/mol. The conformational free energies also were estimated using the observed liquid phase IR spectra and intensities calculated using B3LYP/6-311++G** and MP2/6-311++G**. The rotational free energy profiles for all of the compounds were estimated at the G3-B3 level.     

Heats of formation of beryllium, boron, aluminum, and silicon re-examined by means of W4 theory

Benchmark total atomization energies (TAE0 values) were obtained, by means of our recent W4 theory [Karton, A.; Rabinowitz, E.; Martin, J. M. L.; Ruscic, B. J. Chem. Phys. 2006, 125, 144108], for the molecules Be2, BeF2, BeCl2, BH, BF, BH3, BHF2, B2H6, BF3, AlF, AlF3, AlCl3, SiH4, Si2H6, and SiF4. We were then able to deduce "semi-experimental" heats of formation for the elements beryllium, boron, aluminum, and silicon by combining the calculated TAE0 values with experimental heats of formation obtained from reactions that do not involve the species Be(g), B(g), Al(g), and Si(g). The elemental heats of formation are fundamental thermochemical quantities that are required whenever a molecular heat of formation has to be derived from a calculated binding energy. Our recommended DeltaH degrees f,0 [A(g)] values are Be 76.4+/-0.6 kcal/mol, B 135.1+/-0.2 kcal/mol, Al 80.2+/-0.4 kcal/mol, and Si 107.2+/-0.2 kcal/mol. (The corresponding values at 298.15 K are 77.4, 136.3, 80.8, and 108.2 kcal/mol, respectively.) The Be value is identical to the CODATA recommendation (but with half of the uncertainty), while the B, Al, and Si values represent substantial revisions from established earlier reference data. The revised B and Si values are in agreement with earlier semi-ab initio derivations but carry much smaller uncertainties.     

The dimerization of SnCl2(g): mass spectrometric and theoretical studies

The vaporization of SnCl2(s) was investigated in the temperature range between 382 and 504 K by the use of Knudsen effusion mass spectrometry. The Sn+, SnCl+, SnCl2+, Sn2Cl3+, and Sn2Cl4+ ions were detected in the mass spectrum of the equilibrium vapor. The SnCl2(g) and Sn2Cl4(g) gaseous species were identified, and their partial pressures were determined. The structure and vibrational properties of both species and corresponding fragmentation products were studied applying density functional theory and second-order M?ller-Plesset perturbation theoretical approaches. Molecular parameters yielded thermodynamic functions by the use of statistical thermodynamics. The sublimation enthalpies of SnCl2(g) and Sn2Cl4(g) at 298 K resulting from the second- and third-law methods are evaluated as 130.9 +/- 6.2 kJ mol(-1) and 155.8 +/- 7.3 kJ mol(-1), respectively. The enthalpy changes of the dissociation reactions Sn2Cl4(g) = 2 SnCl2(g) were obtained as delta(d)H degrees(298) = 106.8 +/- 6.2 kJ mol(-1). The corresponding theoretical value amounts to 103.4 kJ mol(-1). The change of monomer properties due to the dimerization reaction is also discussed.