2,3,7,8-四氯苯并二噁英分子结构与热力学性质的理论研究

用密度泛函理论 (DFT)和从头算 (abinitio)方法 ,在B3LYP/ 6 - 31G、B3LYP/ 6 - 31G 、B3LYP/ 6 - 311G 和MP2 / 6 - 31G 水平上全优化计算了 2 ,3,7,8-四氯苯并二英 (2 ,3,7,8-TCDD)的几何构型、电子结构和振动频率 ,并用校正后的频率计算了 2 98～ 15 0 0K的标准热力学函数 ,同时用半经验的PM3SCF -MO进行了同样的计算 。

子结构检索中关系数据库插件的使用和效率

采用关系数据库插件能够实现化合物描述符(FingerPrint)的生成、建立索引和化合物的子结构检索。本文以PubChem有机化合物Molfile为数据源,在Oracle关系数据库上分别安装插件OrChem(JAVA)和Bingo(C^(++))构建了化合物分子结构数据库。本文从FingerPrint的构成和索引策略两方面讨论了OrChem和Bingo的主要差异,并选取10个特征化合物进行子结构检索测试。对存储40万种化合物的分子结构数据库的测试结果显示,OrChem可满足用户检索响应,Bingo则更为快捷。对于存储2600万种化合物的分子结构数据库,针对Bingo通过优化Oracle数据库内存管理、数据表结构、子结构预筛选参数,实现了满足用户的高效检索。

用密度泛函理论研究煤中甲基苯生成甲烷的反应机理

低煤级煤大分子芳香结构单元以1～2个环的芳香体系为主,为了理解煤热解甲烷的生成机制,利用量子化学密度泛函理论方法(DFT)对甲基苯热解甲烷的生成机理进行了热力学和动力学计算,计算结果表明,在生成甲烷的所有反应路径中,其控速步骤是甲基苯的脱氢或脱甲基的过程;氢自由基的参与可以显著的降低甲基苯脱甲基的能垒。在温度低于675K时,生成甲烷的主反应路径为:甲基苯上甲基脱氢,然后由氢通过本位(ipso)加成到甲基苯然后脱甲基,最后由甲基夺取甲基苯侧链上的氢生成甲烷。当温度高于975K时,生成甲烷的主反应路径为:甲基苯脱甲基,然后由甲基夺取甲基苯侧链上的氢生成甲烷。在675～975K之间则为这两条反应路径的竞争反应。

Effects of Doubled_CO_2 Concentration on Ultrastructure, Supramolecular Architecture and Spectral Characteristics of Chloroplasts from Wheat

Wheat ( Triticum aestivum L.) plants were grown under ambient and doubled_CO 2(plus 350 μL/L) concentration in cylindrical open_top chamber to examine their effects on the ultrastructure, supramolecular architecture, absorption spectrum and low temperature (77 K) fluorescence emission spectrum of the chloroplasts from wheat leaves. The results were briefly summarized as follows: (1) The wheat leaves possessed normally developed chloroplasts with intact grana and stroma thylakoid membranes; The grana intertwined with stroma thylakoid membranes and increased slightly in stacking degree and the width of granum, in spite of more accumulated starch grains within the chloroplasts than those in control; (2) The particle density in the stacked region of the endoplasmic fracture face (EFs) and protoplasmic fracture face (PFs) and in the unstacked region the endoplasmic fracture face (EFu) and the protoplasmic fracture face (PFu) was significantly higher than that of control. Furthermore, in some cases many more particles on EFs faces of thylakoid membranes appeared as a paracrystalline particle array; (3) The variations in the structure of chloroplasts were consistent with the absorption spectra and the low temperature (77 K) fluorescence emission spectra of the chloroplasts developed under the doubled_CO 2 concentration. Results indicate that the capability of light energy absorption of chloroplasts and regulative capability of excitation energy distribution between PSⅡ and PSⅠ were raised by doubled_CO 2 concentration. This is very favorable for final productivity of wheat.

Local structure of calcium silicate melts from classical molecular dynamics simulation and a newly constructed thermodynamic model

The distributions of local structural units of calcium silicate melts were quantified by means of classical molecular dynamics simulation and a newly constructed structural thermodynamic model. The distribution of five kinds of Si-O tetrahedra Qi from these two methods was compared with each other and also with the experimental Raman spectra, an excellent agreement was achieved. These not only displayed the panorama distribution of microstructural units in the whole composition range, but also proved that the thermodynamic model is suitable for the utilization as the subsequent application model of spectral experiments for the thermodynamic calculation. Meanwhile, the five refined regions mastered by different disproportionating reactions were obtained. Finally, the distributions of two kinds of connections between Qi were obtained, denoted as Qi-Ca-Qj and Qi-[Ob]-Qj, from the thermodynamic model, and a theoretical verification was given that the dominant connections for any composition are equivalent connections.

Crystal and Molecular Structure of Cyanuric Acid

The title compound [C3H3N3O3·2H2O] was synthesized by the reaction of urea with hydrogen peroxide, and characterized by elemental analysis, infrared spectra and nuclear magnetic resonance. The crystal belongs to monoclinic system,space group C2/c, with a=12. 538(3)i, b=6. 685(1),c=8.807 (3) , β= 116.11(2)°;V=662. 9(4), Z=4, Mr=165.11, Dc=1.65g/cm3, (MOKα)=0. 71069,μ=1. 47 cm-1, F(000) = 344,final R=0. 046 and Rω=0.061 for 493 observable reflections with I>3σ(I). All atoms lie in plane giving the molecule a planar configuration. The bond length of C-O is 1.214(3), C-N is 1.366(3). Every two cyan-uric molecules in the cell are connected by two intermolecular hydrogen bonds N-H…O, with N…O distance of 2.763 , N-H…O angle of 180.0°.

The Crystal and Molecular Structure of Fargesin

Fargesin, C_(21) H_(22)O_6, was extracted from the buds of Magnolia biondii Pamp and its structure was determined by X-ray crystallographic analysis , M_r = 370. 40, monoclinic, P2_1 , a= 9. 737(2) , b= 6. 665(1) , c= 14. 584 (2)A , β=90. 41 (1)°, V= 946. 5 (3) A￣3 Z= 2, F(000) = 392, D_c= 1. 303 g/cm3. The structure was solved by direct methods and refined to a final R= 0. 0358 using 1207 observed reflections with I≥ 3σ(I). The molecule was revealed as a compound of bisepoxy lignan with asymmetrical substitutions. The relative configuration from Xray diffraction analysis was in agreement with that of ￣(13)C NMR spectrum analysis.

C-H…O Hydrogen Bonds and π…π Interaction and the Crystal and Molecular Structures of 3-Nitro-benzylideneaniline-methyl-2’

The title compound (C14H12N2O2, Mr = 240.26) crystallizes in the monoclinic system, space group P21/a with a = 7.394(1), b = 21.334(3), c = 7.423(1) ? b = 89.82(1)? V = 1170.8(3) ?, Z = 4, Dc = 1.363 g/cm3, m(MoKa) = 0.93 cm-1 and F(000) = 504.00. The final R and wR are 0.0440 and 0.1370 for 2153 observed reflections (I > 2s(I)), respectively. The dihedral angle between the two phenyl rings is 52.9 and that between the NO2 group and its attached ring is 3.0. In the crystal, molecules are stacked along [100] through p…p interactions. The CH…O hydrogen bond (3.403 ? 120.4? laterally connects the stacks along [010] to form networks (001) which are further anti- parallelly connected by CH…O (3.382 ? 142.9) and p…p interactions extending along [001]. Also presented here is a brief study on the CH…O hydrogen bonds in nitro-substituted benzyl-ideneanilines which can be classified into five types, namely, )5(12R, )4(21R, )8(22R, )6(12R and )7(22R, with the first three occurring more often.

Molecular reconstruction model based on structure oriented lumping and group contribution methods

Molecular management is a promising technology to face challenges in the refining industry, such as more stringent requirements for product oil and heavier crude oil, and to maximize the value of every molecule in petroleum fractions. To achieve molecular management in refining processes, a novel model that is based on structure oriented lumping(SOL) and group contribution(GC) methods was proposed in this study. SOL method was applied to describe a petroleum fraction with structural increments, and GC method aimed to estimate molecular properties. The latter was achieved by associating rules between SOL structural increments and GC structures. A three-step reconstruction algorithm was developed to build a representative set of molecules from partial analytical data. First, structural distribution parameters were optimized with several properties. Then, a molecular library was created by using the optimized parameters. In the final step, maximum information entropy(MIE) method was applied to obtain a molecular fraction. Two industrial samples were used to validate the method, and the simulation results of the feedstock properties agreed well with the experimental data.

Molecular and Crystal Structure of 1,3,5-Tris(benzimidazol- 1-ylmethyl)-2,4,6-Trimethylbenzene

The compound 1,3,5-tris(benzimidazol-1-ylmethyl)-2,4,6-trimethylbenzene, crystallizes in the monoclinic system, space group P21/c, with a = 17.571(4), b = 10.860(2), c = 14.126(3) ?; ( = 92.89(3)(, V = 2692(1) ?3, Dc = 1.260 g/cm3, Z = 4, C33H30N6, Mr = 510.63, ((MoK() = 0.077mm-1, F (000) = 1080. The structure was refined to R = 0.0592, wR = 0.1379 for 1492 (I(2((I)) reflections. The title molecule has cis, trans, trans-conformation about the central phenyl ring. The screw-related molecules are connected by hydrogen bonds C-H(((N (x, -0.5-y, 0.5+z) and form the infinite helical chains. The polar molecular chains are antiparallelly stacked through edge-to-face C-H…πinteractions.

Crystal and Molecular Structure of N,N-Bis(2-chloroethyl)-N'-isopropyl-N'-phenyl Thioureido Phosphoramide

The molecular structure of N, N-bis ( 2-chloroethyl )-N'-isopropyl-N'-phenyl thioureido phosphoramide has been determined by X-ray diffraction method. The crystal(C_14H_23Cl_4N_4OPS) is monoclinic with space group P21/n,α=13. 398(2) , b= 10. 351(4), c= 14. 595(3) A, β= 101. 45(1)°, V=1983(2) A3 Mr=397. 31, Z=4, Dx=1. 34 g/cm3 , μ= 5. 17 cm-1, F(000) = 832 , R=0. 056 and Rω=0. 060 for 1856 reflections with I≥3σ(Ⅰ).The chemical shifts of the hydrogen atoms bonded to nitrogen atoms N (4) and N (33 are 10. 96 ppm and 7. 57 ppm respectively locating in the lower field. This abnormal situation can be explained by the formation of intramolecular and intermolecular hydrogen bonds. And the X-ray crystallographic analysis demonstrates the existence of the H-bonding six-membered ring in the structure.

Synthesis, Crystal and Molecular Structure of 1,1'- Bis (N-phenylhydroxyaminocarbonyl) ferrocene

bis (N-phenylhydroxyaminocarbonyl) ferrocene has been synthesized by the reaction of phenylhydroxylamine and 1,1'-bis(chlorocarbonyl) ferrocene,and its crystal structure has been determined by X-ray diffraction method. This compound, C24H20FeN2O4, crystallizes in the orthorhombic space group P2121 21 with unit cell parameters a= 8.911 ( 1 ), b=14.045 ( 1 ) ,c=16.259 ( 3 )A, V = 2034.8 (5 )A3,F(000)=944, μ(MoKα) = 7. 72 cm(-1). The calculated density is 1.49g/cm3 for Z=4. In contrast to most previously reported hydroxamic acids that have been structurally characterized, two planar hydroxamic acid groups are in trans with C(O))-N and C-O distances being similar to those found in amides. The stabilization of the trans-conformation of the title compound is ascribed to the steric and electronic interaction between two phenyl rings and strong hydrogen bond hetween the hydroxyl and carbonyl.

Crystal and Molecular Structure of(η~5-C_5H_5)_2Yb(NC_4H_4)(OC_4H_8)

The complex(C_5H_5)2 Yb(NC4H4)(OC_4H_8) crystallizes in orthorhombic system with space group Pnma and a=15.552(4),b=12.491(3),c=8. 711(3),V=1692. 2(7),Z=4 and Dc=1.733 g/cm3. Crystal study has shown that the molecule has crystallographic mirror symmetry.The Yb(Ⅲ) has a distorted tetrahedral coordination geometry.

Crystal Structure and Molecular Structure of Binuclear Copper(Ⅱ) Complex, [Cu (C_5H_5NO) (C_6H_5COO)_2]_2

At room temperature, dibenzoyl peroxide and pyridine N-oxide reacted with metallic copper powder in a mixed solvent(dichloromethane, trichloromethane and tetrahydrofuran), resulting in a binuclear copper(Ⅱ) complex. [Cu (C_5H_5NO)-(C_6H_5COO)_2]_2. The structure of the complex was characterized by elemental analyses.IR spectra and X-ray single crystal analysis. The crystal is triclinic, space group P1,with cell parameters . a= 9. 262(4) ,b= 10. 697(2) , c=10. 881 (3 )A , a=59. 60( 2 ),β= 74. 83 ( 3 ) .Y = 72. 80 ( 2 )°. V= 880. 0 A￣3 . D_c = 1 . 5 20 g/cm￣3 . Z = 1 . μ= 1 2. 7 cm-1, R=0. 044 ,R_w=0. 048 for 3477 reflections with I>3σ(I), M_r=805. 78. Each copper(Ⅱ) atom is coordinated by four bridging bidentate benzoate ligands and one pyridine M-oxide.

Crystal and Molecular Structure of 1-Methyl-4-(2-( 3,4-dimethoxyphenyl) vinyl) pyridinium 4-Tolylsulfonate Dihydrate C_(16)H_(18)NO_2^+·C_7H_7SO_3^-·2H_2O

The crystal structure of the title compound C16H18NO2+·C7H7SO3-·2H2O, (C23H29NSO7, Mr=463.53) has been determined by single-crystal X-ray diffraction analysis. The crystal belongs to the monoclinic system with space group P21/n, a=8.101(1), b=8.958(2), c=33.281(5)?,β= 94.910(1)(, V=2406.3(7)?3, Z=4, Dc=1.279g/cm3, μ=0.176mm-1, F(000)=984, final R=0.0409, and Rw=0.0860 for 4401 independent reflections. The result shows that in the crystal structure of the title compound the planar cations have two configurations with equal occupation ratio and are antiparally packed through π…π interactions. Similar packing energies in A and B are probably the main factor that leads to the disorder structure.

Crystal and Molecular Structure of Methylene-bis[benzobicyclo(diaza-diphenyl) stannoxide],[o-O■n(C_6H_5)_2]_2CH_2·1/2C_6H_6

Methylene-bis[benzobicyclo(diaza-diphenyl) stannoxide,C_(41)H_(34)N_4O_4Sn_2·1/2C_6H_6],Mr=923.19,m.p.126-127℃,triclinic,P1,a=9.780(4),b=14.485(2),c=15.122(6),α=74. 95(3),β=72.21(3),γ=82.68(2)°,V=1967(1) Z=2,Dx=1.56 g/cm￣3, MoKα(λ=0.71073),μ=13.20 cm-1,F(000)=922;final R=0.045, Rw=0.046 for 3637 observed reflections(I≥3σ(I)).The title compound is a bimetallo-heterocyclic complex prepared by condensation.Each tin atom has a trigonal bipyramidal coordination with two oxygen atoms occupying the axial positions.

Crystal and Molecular Structure of OMPCTF

The title compound C_(28)H_(48)O_4 (M_r=448. 8) crystallizes in the triclinic, space group P1 with a=12. 909(5) , b=10. 422(4) , c=11. 052(4) A, α=108. 35 (3), β=100. 07(3), γ=70. 06(3)°, Z=2, V=1322. 9(8) A￣3,109. D_c=1. 13 gcm￣(-3), F(000)=496, μ(MoKa)=0. 80cm￣(-1). The final R=0. 067 and R_w=0. 074 for 1652 observed independent reflections (I≥3σ(I)). The conformation of the molecule is rather unusual , and there is not any symmetry element involved in it.The four units are different from each other in bond lengths and bond angles. The distances between two separate oxygen atoms are 5. 77 and 4. 25 A, respectively , and those between two adjacent oxygen atoms average 3. 59 A.

Structure of Palisadin B,C_(15)H_(24)Br_2O

Palisadin B,a brominated sesquiterpenoid, was isolated from the marine alga genus Laurencia Karlae Zhang et Xia collected from the Nansha Islands of the South China Sea. The structure was examined by MS and NMR spectra and confirmed by X-ray diffraction analysis.C_(15) H_(24) Br_2O, Mr=380.18, tetragonal,P4_12_12, a= 10. 812(3) ,c=27. 436(7),V=3027. 1, Z=8, D_c= 1. 948Mg. m￣(-3) ,μ(MoKa) = 61. 81 cm￣(-1), F(000) =1900,T=296K,final R=0. 050 for 1082 observed reflections. The molecule is composed of a cyclohexane ring fused with a seven-membered cyclic ether, and the latter exhibits a twist boat conformation.The molecules in the crystal lattice are held together by van der Waals forces (m. p.367-368K). Bond lengths and angles are internally consistent and the van der Waals interactions are normal.

Delft Molecular Mechanics Study on the Structures of Monoclinic MF Iand H[ Al] ZSM-5

Delft molecular mechanics minimization has been performed for the study on the structures of monoclinic MFI and H[Al]ZSM 5. The results were compared with those from quantum chemistry and other force field calculations. For the minimization of H[Al]ZSM 5, significant geometric rearrangements have been investigated in the local environments of Brnsted acidic sites, which resulted from the isomorphous substitution of Al for Si atoms in MFI framework.

CRYSTAL AND MOLECULAR STRUCTURE OF A NOVEL Au Ag SUPRACLUSTER COMPOUND [Au_13Ag_12(μ-Br)_4(μ_3-Br)_2(Ph_3P)_10-

[Au13Ag12(μ-Br)1(μ3-Br)2 (Ph3P)10Br2] Br, monoclinic. space group C2/m, a = 36. 496(17). b=16. 878(7), c-=19. 772(9) A , β=99. 87(5)°, V=11998. 9 A3.Z=2. The final R(Rw) is 0. 097(0. 109) for 3779 reflections with I>3σ(I). The structure can he considered as two icosahedral cluster units (AurAg6) sharing one vertex and linked hy six bromine atoms. The Au - Au, Au - Ag. and Ag-Ag distances fall in the ranges of 2. 69-2. 96. 2. 84-3. 02. and 2. 92-3. 26 A, respectively.