密堆积与中学化学中的晶体结构

联系新课程和化学奥赛的有关内容简要论述了晶体结构的密堆积;分析了密堆积在中学化学晶体结构学习中的地位和作用;举例说明了密堆积对于深刻理解晶体结构的内容和在解决晶体结构问题中的应用。     

Crystal Structure of Taxinine A

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雷公藤内酯甲的制备和晶体结构

从雷公藤(TripterygiumwilfordiiHook.F.)根心部分的乙醇提取液中,采用硅胶柱色谱法和TLC方法得到纯的雷公藤内酯甲(WilforlideA).用IR,¹HNMR和元素分析表征,并测定其单晶结构.化合物分子式为C₃₀H₄₆O₃,M_r=454.70,晶体属正交晶系,P2₁2₁2₁空间群,晶胞参数:a=0.732(4)nm,b=1.283(7)nm,c=2.693(6)nm,V=2.5327nm₃,Z=4,D_c=1.192g·cm^-3,μ(MoKα)=0.695cm^-1,F(000)=1107,R=0.039,R_W=0.044,分子为五环三萜γ-内酯.分子中C22-C23为烯键,C11连有羟基,C33_O3为羰基,整个分子呈起伏状,不在同一平面内.从AM1计算结果可以看出,仲羟基中的O1及γ-内酯中的O3原子净电荷大,致使分子极性较大,易在O1和O3部位发生亲核反应和氧化还原反应,显示分子的反应活性     

千解草甲素的晶体和分子结构

千解草(Pygmaeopremna Herbacea)为马鞭草科千解草属植物,分布在中国西南一带,尤以四川南部为多。民间用其茎叶治疗跌打损伤,风湿性关节炎,月经不调,产后瘀血,外感风寒、消化不良等病患,且疗效显著,广为应用。千解草属植物共有五种,均未见有关化学成份的报道。我们从千解草根的乙醚提取物中得到四种晶体,本文报道了具有代表性的千解草甲素的晶体和分子结构(1)。     

Host—guest Complementarity and Crystal Packing of Intercalated Layered Structures

Intercalated layered structures are analyzed in order to estimate the rules governing their crystal packing. An overview is given on structural types of layered intercalates based on various types of host structures and guest species. The factors describing the host–guest complementarity in intercalated layered structures like: the character of active sites, the host–guest and guest–guest interactions, the size of guests and topology of layers are investigated and their effect on crystal packing is illustrated on examples. Special attention will be paid to the conditions for the regular ordering of guests in the interlayer space, as the requirement of structure ordering is of great importance in design of intercalates for special applications, where one has to control the interlayer porosity or electronic properties of guest molecules etc. A method of structure analysis based on a combination of molecular modeling and experiments has been worked out for intercalates. Molecular modeling (force field calculations) in conjunction with experiments (diffraction methods and vibration spectroscopy) enables us to analyze the disordered intercalated structures, where the conventional diffraction analysis fails.     

1,5-苯并硫氮杂-α,α-二甲基-β-内酰胺衍生物的合成、表征及晶体结构

利用异丁酸乙酯、异丁酸异丙酯、异丁酸薄荷醇酯和LDA作用形成烯醇锂盐，然后和1,5-苯并硫氮杂     

细胞毒活性二萜Wangzaozin A的晶体结构

采用单晶X射线衍射技术对对映-贝壳杉烷化合物WangzaozinA的晶体结构进行了研究.研究结果表明,在最小不对称单元中存在两个构象稍有差异(键长和键角不同)的分子,其中两者的3个六元环均为椅式构象,而五元环为扭曲信封式构象.WangzaozinA晶体结构属正交晶系,P2₁2₁2₁空间群,晶胞参数a=0.66485(8)nm,b=2.5796(4)nm,c=1.0473(2)nm,Z=4.分子通过分子内氢键O₃-H₃0…O₂和O₃'-H₃0'…O₂'以及分子间氢键O1-H10…O₃,O1'-H10'…O₃',O₂-H₂0…O₄'和O₂'-H₂0'…O₄形成网络结构,并在晶体中沿c轴排列.体外抗肿瘤实验证实,标题化合物具有显著的细胞毒活性,由SRB法测试其抗Bel-7402及HO^-8910细胞株的IC₅₀值分别为(5.32±0.79)和(4.10±1.00)μmol/L.     

铀氮化物晶体结构及电子结构

铀氮化物因其独特的物理化学性质及优良的性能而成为核燃料循环系统中重要的燃料材料,是核领域的研究热点材料之一。此外,铀氮化物也被用作抗腐蚀涂层材料,在金属铀的表面腐蚀防护领域具有重要的应用价值。在铀-氮体系中,五种结构铀氮化物,包括NaCl型UN、HgIn型UN、Mn₂O₃型α-U₂N₃、La₂O₃型β-U₂N₃和CaF₂型UN₂,已经被确认并进行了广泛研究。但是到目前为止,由于铀氮化物复杂的非化学计量比问题,导致对上述物相之间的转化关系的认识仍不清楚;而不同化学计量比的铀氮化物由于其电子结构的差异,使得其基本物理化学性质发生了根本的变化。有关铀氮化物晶体结构和电子结构方面的研究是探讨其优异性能起因的第一步,因此引起研究者的广泛关注。本文在归纳和分析大量文献的基础上,结合本课题组在铀氮化物相关方面的研究成果,着重介绍铀氮化物晶体结构和电子结构方面的主要进展,并对铀氮化物相结构的转化规律以及电子结构的演化规律进行总结,以期为铀氮化物的实验研究和功能应用提供参考。     

红霉素A6，9-亚胺醚的合成及晶体结构测定

通过红霉素A9（E）-肟（1）的Beckmann重排合成了红霉素A6，9-亚胺醚（2） ，并对2乾地了波谱表征。红霉素A6，9-亚胺醚（2）的X射线衍射单晶结构测定表 明，其结构为正交晶系，P2_12_12_1空间群，晶胞参数：a=1.0646(2) nm, b=1. 7896(4) nm, c=2.3755(5) nm; α=β=γ=90.00(0)°，V=4.5257(16) nm~3， D_c=1.187 g/cm~3，Z=4，F（000）=1776，μ=0.091 mm~(-1), R_1=0.0399, ω R_2=0.0482。     

冬凌草甲素的晶体结构

冬凌草甲素,C_(20)H_(28)O_6,Mr=364.44,是一种从中药中提取的抗癌药,它的晶体结构分析表明晶体属正交晶系的空间群P2_12_12_1,晶胞参数为α=13.316(9),b=21.302(2),c=13.015(1),V=3697(9)~3。Z=8,D_c=1.31g/cm~3,D_o=1.30g/cm~3,F(000)=1568。该分子是四环二萜类化合物,A环和C环是椅型结构,B环是船型结构;D环是部分共轭五员环,为半椅型结构,环上相邻的两个双重键侧基组成一个六原子的共轭平面。     

Crystal Structure of Li-Analcime

Li-analcime Li_1.69Na_0.14[Al_1.83Si_4.17O₁₂] · 2.05H₂O has been prepared and studied by single-crystal X-ray structural analysis: a = 13.510(2), b = 13.520(1), c = 13.503(2) , V = 2466.4(9) ³, Z = 8, space group Pbca. The structure is compared with that of the starting Na-analcime. Lithium atoms lie near Na sites with a distorted octahedral coordination O₄(H₂O)₂. Due to the smaller size of Li atoms, their real environment is differentiated into 3+3 or 4+2. The off-network cations and the H₂O molecules are shifted from the sites which they normally occupy in analcime in a cooperative manner. The changes in the unit cell dimensions and symmetry are explained from crystal-chemical viewpoint.     

Crystal Structure of N-Phenylisothiocyanatido-Phosphonamidothioate

1INTRODUCTIONLawess0n,Sreagent(LR),2,4-Bis(4-meth0xyphenyl)-1,3,2'4-dithiadiphosphetane-2,4-disulfide,notonlyisaselectivereagentf0rthi0natingcar-bonylcompounds,buta1soreactswithcertainsubstratestogivephosph0rushetero-cyclecompoundswhichcontainthe(4-methoxyphenyl)phosphinothi0ylidene"4-CH,OC,H'P(S)"m0iety.Theseheterocycliccompoundshavesomepotentialbiologi-calactivitiesasherbicides,fungicides,andinsecticides[l'2J.Wehavestudiedthecy-clizationofthebifunctionalsubstrateswithLRtogive5-and6…     

螺[1—溴—4—l—孟氧其—5—氧杂—6—氧代双环[3.1.0]已烷2,3‘—（4’—甲氧 …

本文报道了利用新手性还源合成的标题化合物Ｃ２９Ｈ４５ＢｒＯ７（Ｍｒ＝５８５．５６）的晶体结构,该晶体属正交晶系,空间群为Ｐ２１２１２１,晶胞参数α＝９．７４８（４）,ｂ＝１２．５３７（５）,ｃ＝２５．８５１（９）Ａ,Ｖ＝３１５９（２）Ａ＾３,Ｚ＝４,Ｄｘ＝１．２３１ｇ／ｃｍ＾２,μ１．３４１ｍｍ＾－１,Ｆ（０００）＝１２４０,偏离因子Ｒ＝０．０４７５,ＲＷ＝０．０６０９,分子中共有５个环,１２个手     

Crystal Structure of L-Quebrachitol

L-Quebrachitol (1) isolated from the root of Elaeagnus formosana Nakai (Elaeagnaceae) has not been reported before for any species of the genus of Elaeasnus. Its structure was established from spectral data and was completely characterized by single-crystal X-ray analysis. L-Quebrachitol crystallizes in the monoclinic system, space group P2₁, with cell parameters are a = 6.702(4), b = 7.207(4), c = 8.758(5) Å, β = 90.24(5)° and Z = 2.