Synthesis of dialkyl 2,5-dihydro-5-oxo-1,2-azaphosphole-3,4-dicarboxylates

The adducts produced in the reaction between triphenylphosphine and dialkyl acetylenedicarboxylates were trapped by arylsulfonyl isocyanates to produce dialkyl 2,5-dihydro-5-oxo-1,2-azaphosphole-3,4-dicarboxylates in good yields.     

Formation of dimethyl tricyclo[6.2.2.01,7]dodeca-2,4,6,9, 11-pentaene-9, 10-dicarboxylates from azulenes and dimethyl acetylenedicarboxylate under high pressure and thermal rearrangement of the tricyclic compounds into heptalene-1,2-dicarboxylates

Abstract

It is shown that alkylated azulenes (see 1, 12, and 13) react with dimethyl acetylenedicarboxylate (ADM) in hexane under a pressure of 6–7 kbar already at 30° to yield the corresponding dimethyl tricyclo[6.2.2.0^1,7]dodeca-2,4,6,9, 11-pentaene-9, 10-dicarboxylates (see 14, 15, and 16). These compounds decompose in apolar solvents such as decane at temperatures > 50° mainly (>95%) to the starting materials. However, in polar solvents such as MeCN or DMF the formation of the corresponding dimethyl heptalene-1,2-dicarboxylates (see 2, 18, and 20) competes effectively with the decomposition into the starting materials. In polar and protic solvents such as EtOH or O(CH₂CH₂OH)₂ instead of the heptalenes the corresponding (E)-and (z)-configurated dimethyl 1-(l′-azulenyl)-ethylene-l,2-dicarbox-ylates (see 17, 19, and 21) are formed. All experimental findings clearly show that the tricyclic compounds (14 to 16) are the crucial intermediates in the thermal formation of heptalenes from azulenes and ADM and that the heterolytic cleavage of the C(1), C(10) bond in the tricyclic compounds is the rate-determining step in heptalene formation.     

Improved synthesis of diethyl 2,6-dimethyl-4-aryl-4H-pyran-3,5-dicarboxylate under ultrasound irradiation

Diethyl 2,6-dimethyl-4-aryl-4H-pyran-3,5-dicarboxylates (1) have been synthesized by the reaction of aryl aldehyde and 1,3-diketone catalyzed by ZnCl₂ under ultrasound irradiation. The effects of changes in the ultrasonic power, temperature, and reaction time are discussed. With the optimized reaction conditions, various aryl aldehydes were used to synthesize 4H-pyrans (1) under the influence of ultrasound irradiation. Compared with the conventional thermal methods, the remarkable advantages of this method are the simple experimental procedure, shorter reaction time and high yield of product.     

Conformational Analysis of 1,2-Dichlorobutane

Vibrational spectra have been published and normal coordinate calculations have been made for 1,2-dichlorobutane.^1,2 Those calculations were limited to the three conformers that had all four carbon atoms coplanar. Molecular mechanics calculations have now shown a conformer that was omitted to be the second most abundant conformer. Therefore, normal coordinate calculations have been made for this conformer and molecular mechanics calculations have been made for all possible conformers.     

Shape Coexistence in 74Se

The 0 _1,2 ⁺ ,2 _1,2 ⁺ and 4 _1,2 ⁺ states in ⁷⁴Se have been described as linear combinations of pure states with definite deformation within a two-band mixing model. The mixing amplitudes between the spherical and deformed configurations and the mixing matrix elements have then been extracted from the calculations. The exchanged position between the spherical and deformed configurations at I=4 has been obtained within this model.     

Microwave spectrum of 1,2-propanediol

The microwave spectrum of the sugar alcohol 1,2-propanediol (CH₃CHOHCH₂OH) has been measured over the frequency range 6.5–25.0 GHz with several pulsed-beam Fourier-transform microwave spectrometers. Seven conformers of 1,2-propanediol have been assigned and ab initio electronic structure calculations of the 10 lowest energy forms have been calculated. Stark effect measurements were carried out on several of the lowest energy conformers to provide accurate determinations of the dipole moment components and assist in conformer assignment.     

Photoelectron spectra of the gauche and trans conformers of 1,2-bromochloroethane

The HeI photoelectron spectra of the gauche and trans conformers of 1,2-bromochloroethane have been obtained by analysis of time-averaged spectra recorded at different temperatures. Variations in ionization potentials of the two conformers are consistent with data obtained from molecular orbital calculations. Analysis of a HEII spectrum and comparisons with the related molecules 1,2-dichloroethane and 1,2-dibromoethane shows that the ClBr non-bonded interactions include both through-bond and through-space contributions.     

Quantization of surface rust by using laser imaging techniques

Laser speckle interferometry^1,2 and image processing^3,4 have been used to detect and quantize the rust build-up on metal surfaces under water. Speckle information from the sample metal surface was captured by a CCD camera and a frame grabber card. Software techniques were used to convert the image data files into ASCII files in an appropriate format. Three-dimensional surface plots were generated to define the numerical values for the amout of rust build-up.     

Stoichiometrically controlled direct solid-state synthesis of C60H2

The direct solid-state synthesis of C₆₀H₂ has been demonstrated by controlling the amount of hydrogen introduced into the reaction with C₆₀. Palladium hydride has been used as the source of hydrogen. The main product 1,2-C₆₀ is the isomer predicted to have the lowest energy of the possible 23 isomers; in addition, small amounts of the thermodynamically most stable isomer of C₆₀H₄, 1,2,3,4-C₆₀H₄, have also been obtained.     

Effect of Temperature on the Rate of Triplet–Triplet Annihilation of 1,2-Benzanthracene in a Polymer Matrix

The process of triplet–triplet annihilation (TTA) of 1,2-benzanthracene (1,2-BA) incorporated into polymer films of polyvinyl butyral has been investigated in the temperature interval 80–360 K. An analysis of the kinetics of the decay of delayed annihilation fluorescence (DAF) of 1,2-BA has shown that the process of the triplet excitation energy transfer in a disperse medium of the polymer at distant times of the DAF decay can be described using the approximation of random walks of the triplet energy in the inhomogeneous medium of the polymer. At low temperatures, at the initial times of DAF decay the TTA process is described with the aid of a model of static annihilation.     

1,2-聚丁二烯的固态13C-NMR线宽与自由体积

本工作测定了一系列1,2-聚丁二烯样品在不同温度下的固态¹³C-NMR线宽,研究了线宽对链结构和温度的依赖性;发现在一定的温度范围内,线宽与温度的关系符合WLF方程,这表明高聚物的NMR弛豫不仅取决于分子结构,也与自由体积有关。自由体积理论在NMR弛豫中也是适用的。     

Partial wave analysis of ψ' →γχ_(c0) →γpK-Λ used for searching for baryon resonance

Abundant ψ' events have been collected at the Beijing Electron Positron Collider-Ⅱ (BEPCⅡ) that could undoubtedly provide us with a great opportunity to study the more attractive charmonium decays. As has been noticed before, in the process of J/ψ' decaying to the baryonic final states, pK-Λ, the evident Λ* and N* bands have been observed. Similarly, by using the product of χcJ from ψ' radiative decay, we may confirm this or find some extra new resonances. χc0's data samples will be more than χc1,2, taking into account the larger branching ratio of ψ' →γχc0. Here, we provide explicit partial wave analysis formulae for the very interesting channel ψ' →γχc0 →γpK-Λ.     

Competition between associative and dissociative adsorption of 1,2-dihalogenated benzenes on Si(1 0 0)2 × 1: Formation of dihalocyclohexadiene, halophenyl and phenylene adstructures

The room temperature (RT) adsorption of 1,2-difluorobenzene (1,2-DFB), 1,2-dichlorobenzene (1,2-DCB) and 1,2-dibromobenzene (1,2-DBB) on Si(1 0 0)2 × 1 have been investigated by X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD). Both XPS and TPD data show that the relative degree of dissociative to associative adsorption of the dihalogenated benzene (DXB) appears to increase with decreasing electronegativity of the halogen atom (X). In particular, the C 1s intensity ratios for the C-H and C-Si components to the C-X component are found to be 2, 3 and 9.6 for 1,2-DFB, 1,2-DCB and 1,2-DBB, respectively. These results indicate that 1,2-DFB, like benzene, exclusively adsorbs molecularly as a difluorocyclohexadiene adspecies on Si(1 0 0)2 × 1 while 1,2-DBB adsorbs predominantly with double debromination to form 1,2-phenylene. The majority of 1,2-DCB (75%) is found to adsorb molecularly, with the rest (25%) undergone single or double dechlorination to form chlorophenyl and phenylene, respectively. All three DXB molecules appear to have similar coverage as benzene. The two molecular desorption features for 1,2-DFB and 1,2-DCE are observed with desorption maxima at 460 K and 540 K similar to those found for benzene, which suggests that the dihalocyclohexadiene adstructures involve similar bonding through the benzene ring. In accord with the XPS data, no molecular desorption feature is observed for 1,2-DBB on the 2 × 1 surface. Further decomposition of the resulting phenylene adstructures is evident from the desorption fragment, C₂H₂, found at 610 K and 740 K. Recombinative desorption of HCl and HBr above 880 K are also found for 1,2-DCB and 1,2-DBB, respectively. The observed differences between associative and dissociative adsorption for the three DXB adsorbates could be attributed not only to the large difference in the C-X bond strength but also to the relative contributions from inductively withdrawing and resonantly donating electrons exerted by the halogen (X) atoms to the benzene ring.     

Immunochemistry of pathogenic yeast, Candida species, focusing on mannan

This review describes recent findings based on structural and immunochemical analyses of the cell wall mannan of Candida albicans, and other medically important Candida species. Mannan has been shown to consist of α-1,2-, α-1,3-, α-1,6-, and β-1,2-linked mannopyranose units with few phosphate groups. Each Candida species has a unique mannan structure biosynthesized by sequential collaboration between species-specific mannosyltransferases. In particular, the β-1,2-linked mannose units have been shown to comprise a characteristic oligomannosyl side chain that is strongly antigenic. For these pathogenic Candida species, cell-surface mannan was also found to participate in the adhesion to the epithelial cells, recognition by innate immune receptors and development of pathogenicity. Therefore, clarification of the precise chemical structure of Candida mannan is indispensable for understanding the mechanism of pathogenicity, and for development of new antifungal drugs and immunotherapeutic procedures.     

Influence of relaxation effects on probabilities of the 2s2p35S2－2s22p2 3P1，2 intercombination transitions in NII

Transition probabilities of the 2s2p^3 {}^5S_2－2s^22p^2 {}^3P_{1,2} intercombination transitions in NII have been calculated by using a large-scale multiconfiguration Dirac－Fock method. In the calculation the most important effects of relativity, correlation, and relaxation are considered. From the calculated transition probabilities, the lifetime of the 2s2p^3 {}^5S_2 metastable state is derived. The result is in excellent agreement with the latest experimental result. In the meantime the influence of anomalously strong relaxation effects on probabilities of the 2s2p^3 {}^5S_2－2s^22p^2 {}^3P_{1,2} lines in NII have been found.     

The Polarized Infrared Spectrum of Single Crystals of Bis-(N-Methylsalicylaldiminato)-Nickel(II)

The properties and molecular structure of the metal complexes of Schiff-bases of the type N-alkyl- and N-aryl-salicylaldimine have elicited considerable interest:in particular their vibrational spectra have been the subject of many investigations ^1,2. Earlier assignments were made empirically, but recently the ¹⁵ N isotopic shift technique has also been used.     

An infrared band sensitive to regularity in polyacrylonitrile

Polyacrylonitrile (PAN) represents a particular challenge to any-one desiring to determine the nature of the order existing in polymers With X-ray and electron diffraction, only a few reflections are observed [1,2]. Questions of the type of order and whether or not it is truly crystalline in the three-dimensional sense still stimulate considerable controversy [1,2]. Infrared spectroscopic studies [3-61 of PAN have been limited by availability of regularity bands. We have recently observed a band in the infrared spectra of PAN which is sensitive to ordering. It is our purpose to report this observation so that other workers may make use of this band in their efforts to further characterize PAN.     

钐-富勒烯插入化合物的拉曼光谱

采用固态反应法合成了名义组分为SmxC60 (x =1 ,2 ,...,6 )的插入化合物 ,获得了具有正交结构的Sm2 .75C60 超导相和具有体心立方结构的Sm6C60 相。较高Sm浓度的SmxC60 (x≥ 3 )的拉曼谱峰的展宽与减弱可归因于C60 分子的畸变和电 -声子相互作用。拉曼光谱的结果还表明 ,尽管SmxC60 (x =2 ,3 ,4,5 )暴露空气后转变为非晶态 ,但C60 分子畸变反而减小 ;在Sm6C60 非晶态中C60 分子即使存在 ,但其畸变仍然很大 ,或C60 分子已遭到破坏并形成了某种非晶碳化物     

含O3MoS3单元的配合物[Mox（CO）y（O,S—C6H4—1,2）3FezLm[^n—（x=1,2或3,y=0,3

用红外光谱研究标题配合物的结构,得到了很有意义的结果。     

Cerebral magnetic fields associated with voluntary limb movements in man

Summary Voluntary limb movements are preceded by MEG shifts beginning even as early as 1.2 s before the movement. These shifts reverse polarity above the cortical motor representation area of the limb concerned. Preliminary reports of this study have been presented (1,2).