SYNTHESIS AND CRYSTAL STRUCTURE OF 5, 10, 15, 20, 22, 24-HEXAHYDRO-5, 5, 10, 10, 15, 15, 20, 20-OCTAMETHYL-PORPHINE

<正> The title com pound (HHOMP) has been synthesized with the pho-toinduced condensation of acetone and pyrrole in the presence of iodoaromatic hydrocarbons, and its molecular and crystal structures have been determined by X-ray analysis. C28H36N4, Mr = 428. 63, triclinic; space group P1; a =10. 165(3), b = 10. 185(2), c=13. 012(3)(?); α=85. 41(2), β=67. 84(2), γ= 89. 75(2)°; V = 1243 (?)3; Z = 2; D = 1. 145g. cm-3; μ= 0. 635cm-1; F (000) = 464. Although the HHOMP molecule twists, it is found that the four nitrogen atoms are still in a plane.     

Optimization of parameters for semiempirical methods. III Extension of PM3 to Be,Mg, Zn,Ga, Ge,As, Se,Cd, In,Sn, Sb,Te, Hg,Tl, Pb,and Bi

Using a recently developed procedure for optimizing parameters for semiempirical methods,¹ PM3 has been extended to a total of 28 elements. Average ΔH_f errors for the newly parameterized elements are Be: 8.6, Mg: 8.4, Zn: 5.8, Ga: 14.9, Ge: 11.4, As: 8.5, Se: 11.1, Cd: 2.6, In: 11.3, Sn: 9.0, Sb: 13.7, Te: 11.3, Hg: 6.8, Tl: 6.5, Pb: 7.4, and Bi: 10.9 kcal/mol. For some elements the paucity of data has resulted in a method, which, while highly accurate, is likely to be only poorly predictive.     

Mackay,Anti-Mackay,Double-Mackay,Pseudo-Mackay,and Related Icosahedral Shell Clusters

Mackay introduced two important crystallographic concepts in a short paper published 40 years ago. One is the icosahedral shell structure (iss) consisting of concentric icosahedra displaying fivefold rotational symmetry. The number of atoms contained within these icosahedral shells and subshells agrees well with the magic numbers in rare gas clusters, (C₆₀) _N molecules, and some metal clusters determined by mass spectroscopy or simulated on energy considerations. The cluster of 55 atoms within the second icosahedral shell occurs frequently and has been called Mackay icosahedron, or simply MI, which occurs not only in various clusters, but also in intermetallic compounds and quasicrystals. The second concept is the hierarchic icosahedral structures caused by the presence of a stacking fault in the fcc packing of the successive triangular faces in the iss. For instance, a fault occurs after the ABC layers resulting an ABCB packing. This is, in fact, a hierarchic icosahedral structure of a core icosahedron connected to 12 outer icosahedra by vertex sharing, or an icosahedron of icosahedra (double MI. Contrary to Mackay's iss, a faulted hierarchic icosahedral shell is, in fact, a twinlike face capping of the underlying triangles; it is, therefore, called an anti-Mackay cluster. The hierarchic icosahedral structure in an Al-Mn-Pd icosahedral quasicrystal has a core of body-centered cube rather than an icosahedron and, therefore, is called a pseudo-Mackay cluster. The hierarchic icosahedral structures have been studied separately in the past in the fields of clusters, nanoparticles, intermetallic compounds, and quasicrystals, but the underlying geometry should be the same. In the following a unified geometrical analysis is presented.     

3,3,6,6-四甲基-4a-羟基-9-邻甲氧基苯基-1,8-二氧代-2,3,4,4a,5,6,7,8,9,9a-十氢化-1H-氧杂蒽的合成和晶体结构

标题化合物C24H30O5是由邻甲氧基苯甲醛与5，5-二甲基-1，3-环己二酮在N，N-二甲基甲酰胺中反应而得。结构通过单晶X-射线衍射法确定，其晶体属于单斜晶系，空间群C2／c，a=33．942（6），b=7273（1），c=22667（4）A，β=128．989（9）°，Mr=398．50，V=4349（1）A3，Dc=1．2179·cm-3，Z=8，μ（MoKa）=840mm－1，F（000）=1712。晶体结构用直接法解出，经用全矩阵最小二乘法对原子参数进行修正，最后的偏离因子为R=0.043，Rw=0．052。在晶体结构中，存在一个分子间氢键。     

Carboxyketenes, methyleneketenes, vinylketenes, oxetanediones, ynols, and ylidic ketenes from Meldrum's acid derivatives

It has been documented that 5-methylene-Meldrum's acid derivatives (1, 12 ) and their enols (2, 13) can undergo fragmentation to malonic anhydrides (4, 19 ), carboxyketenes (3, 16) and methyleneketene (5, 21 , 35 ), as well as cyclization to pyrrole-3-one and thiophene-3-one derivatives 11a,b (but not furan-3-ones 11c ) under the conditions of flash vacuum thermolysis (FVT). Here we report theoretical calculations at the B3LYP/6-311 + G(2d, p) and G3X(MP2) levels of theory, which allow a rationalization of these observations. The calculated activation barriers for these reactions are all of the order of 37-40 kcal mol(-1). Hydroxyacetylenes (alkynols) 7 are sometimes observed in FVT reactions of Meldrum's acid derivatives. Their formation is now explained as an FVT reaction of the carboxyketenes (e.g. 3-->7 and 32-->34) with a calculated activation barrier of ca. 39 kcal mol(-1). The cyclization of alkylamino- and alkylthio-substituted methyleneketenes 8a,b to pyrrolone and thiophenone derivatives 11a,b is found to be energetically very feasible under FVT conditions, and even in some cases in solution, with activation barriers of 33-39 kcal mol(-1). This cyclization takes place via the fleeting ylidic ketene intermediates 9a,b,25, and 37a,b, which exist in very shallow energy minima. Alkoxy-substituted methyleneketenes 8c do not cyclize in this manner due to the rather high, but in principle not impossible, activation barriers for the initial 1,4-H shifts to the ylidic ketenes 9c (ca. 47 kcal mol(-1)).     

Syntheses, structures, and physical properties of LnAsTe (Ln = La, Pr, Sm, Gd, Dy, Er)

Six rare-earth arsenic tellurides have been synthesized by the reactions of the rare-earth elements (Ln) with As and Te at 1123 K. LaAsTe (a = 7.8354(11) A, b = 4.1721(6) A, c = 10.2985(14) A, T = 153 K), PrAsTe (a = 7.728(2) A, b = 4.1200(11) A, c = 10.137(3) A, T = 153 K), SmAsTe (a = 7.6180(16) A, b = 4.0821(9) A, c = 9.991(2) A, T = 153 K), GdAsTe (a = 7.5611(15) A, b = 4.0510(8) A, c = 9.920(2) A, T = 153 K), DyAsTe (a = 7.4951(13) A, b = 4.0246(7) A, c = 9.8288(17) A, T = 153 K), and ErAsTe (a = 7.4478(1) A, b = 4.0078(1) A, c = 9.7552(2) A, T = 153 K) crystallize with four formula units in the orthorhombic space group D2h16-Pnma. These compounds are isostructural and belong to the beta-ZrSb2 structure type. In each compound, the Ln atoms are coordinated by a tricapped trigonal prism of four As atoms and five Te atoms. The entire three-dimensional structure is built up by the motif of the LnAs4Te5 tricapped trigonal prisms. Infinite nonalternating zigzag As chains are found along the b axis, with As-As distances in these compounds ranging from 2.5915(5) to 2.6350(9) A. Conductivity measurements in the direction of these As chains indicate that PrAsTe is metallic whereas SmAsTe and DyAsTe are weakly metallic. Antiferromagnetic transitions occur in SmAsTe and DyAsTe at 3 and 9 K, respectively. DyAsTe above 9 K follows the Curie-Weiss law.     

RM1: a reparameterization of AM1 for H, C, N, O, P, S, F, Cl, Br, and I

Twenty years ago, the landmark AM1 was introduced, and has since had an increasingly wide following among chemists due to its consistently good results and time-tested reliability--being presently available in countless computational quantum chemistry programs. However, semiempirical molecular orbital models still are of limited accuracy and need to be improved if the full potential of new linear scaling techniques, such as MOZYME and LocalSCF, is to be realized. Accordingly, in this article we present RM1 (Recife Model 1): a reparameterization of AM1. As before, the properties used in the parameterization procedure were: heats of formation, dipole moments, ionization potentials and geometric variables (bond lengths and angles). Considering that the vast majority of molecules of importance to life can be assembled by using only six elements: C, H, N, O, P, and S, and that by adding the halogens we can now build most molecules of importance to pharmaceutical research, our training set consisted of 1736 molecules, representative of organic and biochemistry, containing C, H, N, O, P, S, F, Cl, Br, and I atoms. Unlike AM1, and similar to PM3, all RM1 parameters have been optimized. For enthalpies of formation, dipole moments, ionization potentials, and interatomic distances, the average errors in RM1, for the 1736 molecules, are less than those for AM1, PM3, and PM5. Indeed, the average errors in kcal x mol(-1) of the enthalpies of formation for AM1, PM3, and PM5 are 11.15, 7.98, and 6.03, whereas for RM1 this value is 5.77. The errors, in Debye, of the dipole moments for AM1, PM3, PM5, and RM1 are, respectively, 0.37, 0.38, 0.50, and 0.34. Likewise, the respective errors for the ionization potentials, in eV, are 0.60, 0.55, 0.48, and 0.45, and the respective errors, in angstroms, for the interatomic distances are 0.036, 0.029, 0.037, and 0.027. The RM1 average error in bond angles of 6.82 degrees is only slightly higher than the AM1 figure of 5.88 degrees, and both are much smaller than the PM3 and PM5 figures of 6.98 degrees and 9.83 degrees, respectively. Moreover, a known error in PM3 nitrogen charges is corrected in RM1. Therefore, RM1 represents an improvement over AM1 and its similar successor PM3, and is probably very competitive with PM5, which is a somewhat different model, and not fully disclosed. RM1 possesses the same analytical construct and the same number of parameters for each atom as AM1, and, therefore, can be easily implemented in any software that already has AM1, not requiring any change in any line of code, with the sole exception of the values of the parameters themselves.     

Instrumental neutron activation determination of Pt, Ru, Ir, Sc, Cr, Fe, Co, La, Ce, Nd, Sm, Yb, Lu, Hf and Ta employing CIRUS reactor as a thermal neutron source

An accurate and simple method has been developed for the determination of Pt, Ru, Ir and other elements employing instrumental neutron activation analysis (INAA). Nondestructive analysis has been carried out for the determination of these elements in different rock samples such as Dolerite, Dyke Dolerite, Country Basalt, Hyaloclastite, Trachyte, Ijolite, Spillite, Diorite and Lamprophyre from various locations like Daman, Tapti, Murud, Talasari, Ranala and Bassein in Maharashtra state. High flux provided by the CIRUS reactor (1×10¹³ n cm^–2s^–1) has been used for thermal neutron bombardment followed by radioassaying of the (n,) products on a HPGe detector coupled to a PC-based MCA unit.     

Acidity trends in alpha,beta-unsaturated sulfur, selenium, and tellurium derivatives: comparison with C-, Si-, Ge-, Sn-, N-, P-, As-, and Sb-containing analogues

The gas-phase acidity of CH3-CH2XH (X=S, Se, Te), CH2=CHXH (X=S, Se, Te) and PhXH (X=S, Se) compounds was measured by means of Fourier transform ion cyclotron resonance mass spectrometry. To analyze the role that unsaturation plays on the intrinsic acidity of these systems, a parallel theoretical study, in the framework of the G2 and the G2(MP2) theories, was carried out for all ethyl, ethenyl (vinyl), ethynyl, and phenyl O-, S-, Se-, and Te-containing derivatives. Unsaturated compounds are stronger acids than their saturated analogues, because of the strong pi-electron donor ability of the heteroatoms that contributes to a large stabilization of the unsaturated anions. Ethynyl derivatives are stronger acids than vinyl compounds, while phenyl derivatives have an intrinsic acidity intermediate between that of the corresponding vinyl and ethynyl analogues. The CH2=CHXH vinyl compounds (enol-like) behave systematically as slightly stronger acids than their CH3-C(H)X (keto-like) tautomers. Vinyl derivatives are stronger acids than ethyl compounds, because the anion stabilization attributable to unsaturation is greater than that undergone in the neutral compounds. Conversely, the enhanced acidity of the ethynyl derivatives with respect to the vinyl compounds is due to two concomitant effects, the stabilization of the anion and the destabilization of the neutral compound. The acidities of ethyl, vinyl, and ethynyl derivatives containing heteroatoms of Groups 14, 15, and 16 of the periodic table are closely related, and reflect the differences in electronegativity of the CH3CH2-, CH2=CH-, and CH[triple chemical bond]C- groups.     

Instrumental neutron activation determination of Pt,Ru, Ir,Sc, Cr,Fe, Co,La, Ce,Nd, Sm,Yb, Lu,Hf and Ta employing CIRUS reactor as a thermal neutron source

An accurate and simple method has been developed for the determination of Pt, Ru, Ir and other elements employing instrumental neutron activation analysis (INAA). Nondestructive analysis has been carried out for the determination of these elements in different rock samples such as Dolerite, Dyke Dolerite, Country Basalt, Hyaloclastite, Trachyte, Ijolite, Spillite, Diorite and Lamprophyre from various locations like Daman, Tapti, Murud, Talasari, Ranala and Bassein in Maharashtra state. High flux provided by the CIRUS reactor (1×10¹³ n cm^?2s^?1) has been used for thermal neutron bombardment followed by radioassaying of the (n,γ) products on a HPGe detector coupled to a PC-based MCA unit.     

Transition-metal-free O-, S-, and N-arylation of alcohols, thiols, amides, amines, and related heterocycles

A new protocol for the Ullmann-type arylation process of different aromatic heterocycles without any transition-metal catalyst, implying the use of a combination of an excess of potassium hydroxide and dimethyl sulfoxide, is described. The reaction can be performed between a broad range of starting nucleophiles including phenol, alcohols, amines, nitrogen-containing five-membered systems such as pyrazoles, imidazoles, and indoles, and amides with haloarenes, iodide and bromide derivatives giving the best results, the possible pathway involving the in situ generation of the corresponding benzyne intermediate. When the reaction was performed with 2-iodoaniline and either carboxamides or isothiocyanato derivatives, the corresponding benzoazole derivatives were obtained.     

3,3,6,6-四甲基-9-邻氯苯基-1,8-二氧代-3,4,5,6,7,9-六氧化氧杂蒽的合成和晶体结构

标题化合物C23H25对O3Cl是由邻氯苯甲醛与5，5-二甲基1，3-环己二酮在N，N-二甲基甲酸腹中反应而得。结构通过单晶X-射线衍射法确定，其晶体属于单科晶系，空间群=1632。晶体结构用直接法解出，使用全矩阵最小二乘法对原子参数进行修正，最后的偏离因子为R=0．054，Rw一0．063。在晶体结构中，吡喃环与苯环之间的两面角为92．43°。     

Syntheses, thermal stability, and structure determination of the novel isostructural RBa3B9O18 (R = Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb)

A novel borate compound YBa(3)B(9)O(18) has crystallized in a melt of BaYB(9)O(16). Single-crystal X-ray diffraction measurements reveal that YBa(3)B(9)O(18) adopts a hexagonal space group P6(3)/m with cell parameters of a = 7.1761(6) A and c = 16.9657(6) A. The structure is made up of the planar B(3)O(6) groups parallel to each other along the (001) direction, regular YO(6) octahedra, and irregular BaO(6) and BaO(9) polyhedra to form an analogue structure of beta-BaB(2)O(4). A series of isostructural borate compounds RBa(3)B(9)O(18) (R = Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb) were prepared by powder solid-state reactions. The DTA and TGA curves of YBaB(9)O(16) show an obvious weight loss at about 955 degrees C associated with a decomposition into YBO(3), B(2)O(3), and YBa(3)B(9)O(18) due to its incongruent melting behavior. The DTA and TGA curves of YBa(3)B(9)O(18) show that it is chemically stable and a congruent melting compound. A comparison of the structures of YBa(3)B(9)O(18) and beta-BaB(2)O(4) is presented.     

Direct determination of traces of Ag, Cd, Pb, Bi, Cr, Mn, Co, Ni, Li, Be, Cu and Sb in environmental waters and geological materials by simultaneous multi-element graphite furnace atomic absorption spectrometry with Zeeman-effect background correction

A method was developed for direct determination of minor and trace amounts of Cr, Mn, Cu, Ni, Co, Li, Pb, Cd, Bi, Sb, Be and Ag in silicate rock, lake and stream sediments using a microwave oven dissolution method and a multi-element graphite furnace atomic absorption spectrometer equipped with a Zeeman-effect background correction device. The measurement technique was also suitable for direct determination of trace and ultra-trace amounts of these elements in drinking and seawater samples. A rock or sediment sample was brought into solution in a Teflon vessel by heating in a microwave oven with a mixture of hydrofluoric acid and aqua regia, followed by a further heating with a mixture of boric acid and ethylenediaminetetraacetic acid. The specified elements were directly determined in a group of four elements in one firing and eight elements in two firings from this solution or from a diluted solution using the optimum operating parameters developed in this work. The method, tested with 23 international reference rocks and sediments and seven international quality control and reference water samples, showed good to excellent agreement with the recommended values.     

Hybrid microdevice electrophoresis of peptides, proteins, DNA, viruses, and bacteria in various separation media, using UV-detection

Recently we described the design of a hybrid microdevice for micro(nano)electrophoresis and electrochromatography, discussed its advantages and disadvantages compared to conventional microdevices and presented a few applications with low-molecular-weight samples. In this paper, we demonstrate the broad application range of this device using UV-based analyses of (i) peptides by free-zone electrophoresis and electrophoresis in a recently introduced gel (polyacrylamide cross-linked with allyl-beta-cyclodextrin), (ii) proteins by electrophoretic molecular-sieving in a polymer solution supplemented with SDS, (iii) DNA fragments by electrophoresis in the above gel, (iv) virus particles in this gel, as well as in free buffer and (v) bacteria in free buffer. To illustrate the advantages of the hybrid microdevice we can mention that electrophoresis of proteins in a polymer-containing buffer, supplemented with sodium dodecyl sulfate (SDS), in a 4.30 (2.75) cm long channel gave a resolution similar to that in conventional capillary electrophoresis in a 23.5 (18.6) cm long capillary and analysis times which were 15-fold shorter.     

Simultanbestimmung von Si, Mn, P, Cu, Al, Ni, Cr, Mo, V, Ti, Co und As in St?hlen mit ICP-AES

Summary A universal method for quantitative analysis of twelve elements in low-alloy steels is described. The samples are digested in a mixture of sulfuric-/nitric acid/ammonium peroxodisulfate. Si, Mn, P, Cu, Al, Ni, Cr, Mo, V, Ti, Co, As are determined in solution by ICP-AES. The procedure was tested with NBS and BCS reference samples. The analytical results are in good agreement with the certified values. With slight modifications, the method is applicable to the analysis of high-alloy steel samples.     

KCl-NaCl(1:1mol)-RECl3熔体的电导率(RE=La、Ce、Pr、Nd、Sm、Eu、Gd、Tb、Dy、Ho、Er、Tm、Yb、Lu、Y、Ce族、Y族)

用交流电桥法测定了熔融KCl-NaCl(1:1摩尔)-RECl₃的电导。比电导的温度函数表达式如下: κ=A+B(t-700) κ:比电导(Ω^-1·cm^-1);t:温度(700—850℃); A、B:本文给出的常数。讨沦了实验值与计算值的偏差,当稀土氯化物在熔体中的浓度为10—50重量百分数时可能形成了络合物。     

Amaryllidaceae,sceletium, imidazole,oxazole, thiazole,peptide and miscellaneous alkaloids

This review covers alkaloids classified in the plant families Amaryallidaceae and Sceletium. In addition alkaloids possessing imidazole, oxazole and thiazole structures are listed followed by alkaloids possessing peptide linkages. Finally miscellaneous alkaloids include those compounds found naturally which cannot be classified into known groups; a relative Pandora's box. A total of 620 structures has been reviewed from 218 references found in the literature for the period July 1999 to June 2000.     

Calorimetry of nanoparticles,surfaces, interfaces,thin films,and multilayers

Calorimetry gives insight into the stability of nanophase materials. Using TiO₂ as an example, the interplay of energetics of polymorphism, surface energy, and surface hydration is discussed. Oxide melt solution calorimetry, water adsorption calorimetry, and adiabatic heat capacity studies together show the following. The metastability of bulk polymorphs increases in the order rutile, brookite, anatase, while the surface energy increases in the opposite order. This leads to crossovers in phase stability at the nanoscale, which appears to be a general phenomenon. Hydration plays a major role in stabilizing nanoparticles and the first layers of water are tightly bound. There is little excess heat capacity and no significant excess vibrational entropy in nanophase rutile or anatase. Further applications of calorimetry to thin films, interfaces, multilayers, and sub-milligram samples are presented.     

Synthesis of xyloketal A, B, C, D, and G analogues

A series of demethyl analogues of the natural products xyloketal A, B, C, D, and G have been prepared in a notably direct manner from 3-hydroxymethyl-2-methyl-4,5-dihydrofuran and a series of corresponding phenols. These syntheses featured a boron trifluoride diethyl etherate-promoted electrophilic aromatic substitution reaction as a key step. In the case of the synthesis of analogues of xyloketal A, the process was found to be highly efficient (up to 93% yield). The optimized isolated yield of these reaction products is remarkable in view of the fact that this transformation involves, minimally, six individual reactions. Moreover, these synthetic studies provide significant insight into the possible biogenic origin of the xyloketal natural products.