X-ray and IR spectroscopic studies of specific intermolecular interactions inN′-substituted isonicotinohydrazides

_N-Thenylidene- andN-(o-nitrobenzylidene)hydrazides of isonicotinic acid have been studied by X-ray structural analysis and IR spectroscopy. In the crystalline state, these molecules are linked through intermolecular N—H ... Np_y hydrogen bonds. Carbonyl groups are not involved in intermolecular hydrogen bonds. However, it was found that the C=O group participates in an attractive interaction with the sulfur atom of the thiophene group. The energy of this interaction is comparable with the energies of intermolecular C=O ... H—N hydrogen bonds in amides.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 896–900, April, 1996.     

Molecular structures of β-amino-α-bromovinyl trifluoromethyl ketones

The molecular structures of β-amino-α-bromovinyl trifluoromethyl ketones was studied by UV, IR, ¹H, ¹³C, and ¹⁵N NMR spectroscopy and using the density functional (B3LYP/6-31G(d,p) and PBE/QZ3P) and ab initio riMP2/cc-pVTZm quantum-chemical calculations. Factors affecting stabilization of the EZE-conformation of the molecules, which is atypical of analogous unsubstituted amino enones, are considered.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 102–106, January, 2005.     

Interpretation of Strengthening Mechanism of Densified Wood from Supramolecular Structures

In this study, densified wood was prepared by hot pressing after partial lignin and hemicellulose were removed through alkaline solution cooking. The tensile strength and elastic modulus of densified wood were improved up to 398.5 MPa and 22.5 GPa as compared with the original wood, and the characterization of its supramolecular structures showed that the crystal plane spacing of the densified wood decreased, the crystallite size increased, and the maximum crystallinity (CI) of cellulose increased by 15.05%; outstandingly, the content of O(6)H⋯O(3′) intermolecular H-bonds increased by approximately one-fold at most. It was found that the intermolecular H-bond content was significantly positively correlated with the tensile strength and elastic modulus, and accordingly, their Pearson correlation coefficients were 0.952 (p < 0.01) and 0.822 (p < 0.05), respectively. This work provides a supramolecular explanation for the enhancement of tensile strength of densified wood.     

Unusual Reactivities of ortho-Hydroxy-β-nitrostyrene

Nitrostyrene derivatives are widely used in organic syntheses as a substrate for Michael addition, photoisomerization and cycloaddition. In contrast, ortho-hydroxy derivatives exhibit unusual behaviors in these reactions. Conjugate addition proceeded upon treatment of the ortho-hydroxy-β-nitrostyrene with an amine; however, subsequent C–C bond cleavage readily occurred to afford the corresponding imine. Moreover, conversion of the trans-isomer to a cis-isomer did not occur efficiently, even when UV light was irradiated. We studied these unusual behaviors of β-nitrostyrene, focusing on the role of the ortho-hydroxy group.     

Approach for the Direct Synthesis of β-Dichlorosubstituted Acetanilides Using Iodine Trichloride (ICl3) as the Oxidant and Catalyst

A reliable method for direct synthesis of β‐dichlorosubstituted acetanilides is reported. The key transformation involves the oxidative and catalytic cleavage of a carbon‐carbon bond in the presence of iodine trichloride (ICl₃). In this protocol ICl₃ is used not only as the catalyst but also as the oxidant which widely broadens the scope of its application in organic synthetic chemistry.     

Synthesis and Structure of Bis(2-Amino-5-Cyanopyridinium) Diaquadichlorocopper(II) Dichloride

The reaction of CuCl₂ with 2-amino-5-cyanopyridine and HCl in 1-propanol gave bis(2-amino-5-cyanopyridinium) diaquadichlorocopper(II) dichloride (1). Crystal data for 1 are: monoclinic, space group: P2₁/c, a = 8.461(3) Å, b=14.665(5) Å, c=7.883(3) Å, g =96.105(4)°, V=972.6(6) Å 3 , Z=2, D_calc =1.645 Mg/m³, w =1.691 mm^?1, F(OOO)=486, MoK _f( u =0.71073 Å), R1=0.0431 for [∣I∣ S 2 σ (I)] and R1=0.0680 for all 1944 unique reflections and 130 parameters. The structure exists as square planar Cu(H₂O)₂Cl₂ units with long semi-coordinate bonds to the cyano nitrogens of the 2-amino-5-cyanopyridinium ions. Hydrogen bonding from the water molecules and N―H hydrogens to the chloride irons stablises the lattice.     

烃类化合物碳氢键解离焓的密度泛函理论研究

通过比较10种密度泛函方法对烃类化合物碳氢键解离焓的计算精度, 发现新型密度泛函BMK方法具有最高的计算精度. 利用该方法计算了包含饱和链烃,、不饱和链烃、脂环烃和芳香烃在内的172个烃类化合物的碳氢键解离焓,计算均方根误差仅为7.95 kJ•mol^－1, 线性拟合常数为0.985. 通过自然键轨道法分析发现, 烃类物质的碳氢键解离焓与母体的碳氢键杂化轨道成分p%, 自由基奇电子轨道杂化成分p%及自由基的自旋密度三个参数之间存在较好的定量关系. 此外, 饱和链烷烃及不饱和链烃的碳氢键解离焓与碳氢键键长之间也存在较好的线性关系.     

Cellular automata approach to site percolation on ℤ2. A numerical study

We present a cellular automata model as a new approach to Bernoulli site percolation on the square lattice. A new macroscopic quantity is defined and numerically computed at each level step of the automata dynamics. Its limit manifests a critical behavior at a value of the site occupancy probability quite close to those obtained for site percolation on ² with the best-known numerical methods.     

一新型金属有机化合物在皮秒激光下的三阶非线性光学性质研究

利用皮秒激光光源,采用z扫描技术研究了一种新型金属有机化合物的三阶非线性光学性质以及光限幅特性.z扫描研究结果表明,这种化合物在1064 nm波长激光激发下的三阶非线性极化率χ(3)为3.8×１０-14 esu,并且存在双光子吸收.光限幅实验结果显示双光子吸收和非线性折射两种不同机制决定了该化合物的光限幅特性.