Nucleation of the β-modification of isotactic polypropylene

The effects of the organic pigments C.I.P. RED 177 and C.I.P. Yellow 83 as nucleating agents on the crystallization of polypropylene were studied by DSC. The anthraquinone pigment exerted a significant effect, resulting in structural modifications with lower melting point, and particularly the t/l4l423494051gl11/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-modification. The DSC curves exhibit four transition regions, with the following temperature intervals: I. 415–417 K, II. 423–425 K, III. 430–432 K and IV. 438–439 K. For evaluation of the t/l4l423494051gl11/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-nucleation effect of pigments, the ratio (t/l4l423494051gl11/xxlarge916.gif" alt="Delta" align="BASELINE" BORDER="0">H ₁+t/l4l423494051gl11/xxlarge916.gif" alt="Delta" align="BASELINE" BORDER="0">H ₂)/(t/l4l423494051gl11/xxlarge916.gif" alt="Delta" align="BASELINE" BORDER="0">H ₃+t/l4l423494051gl11/xxlarge916.gif" alt="Delta" align="BASELINE" BORDER="0">H ₄) was suggested.     

Simultaneous quantitative measurement of a new platelet activating factor antagonist (BN 50730) and its two main metabolites in human plasma and urine by LC-MS

Summary A simple and sensitive assay has been developed for the quantitative measurement of a new platelet activating factor antagonist (BN50730), and its two main metabolites (BN50727 and BN50922), at the picomole level in human plasma and urine. The three compounds of interest and the internal standard (BN50765) were measured by combined LC-negative chemical ionization MS. A simple solid-liquid extraction procedure was used to isolate the parent drug and the two metabolites. The MS was tuned to monitor the intense ionm/z 333 generated in the ion source by a dissociative capture process. The assay was on 1 ml plasma or 0.1 ml urine and the quantitation limit was calculated as 1 ng·ml^–1. The very low relative standard deviations and mean percentages of error calculated for within-day or between-day repeatability assays demonstrate the ruggedness of the technique for routine determination in biological fluids. Some preliminary results on the pharmacokinetics of the parent drug and its two main metabolites illustrate the applicability of this method.     

Li2Br(NH2): Das erste ternäre Alkalimetallamidhalogenid

Li₂Br(NH₂): The First Ternary Alkali Metal Amide Halide The pseudobinary system LiNH₂/LiBr was investigated by X-ray methods. The crystal structure of the compound Li₂Br(NH₂) was solved by single crystal data: Li₂Br(NH₂): Pnma, Z = 8, a = 12.484(2) Å, b = 7.959(1) Å, c = 6.385(1) Å, Z(F_o) with (F_o)² ≧ 3σ(F_o)² = 348, Z (parameter) = 51, R/R_w = 0.019/0.021 Li₂Br(NH₂) crystallizes in a new type of structure. To one another isolated chains of t/02ada61c-f9af-42fc-96fd-dc8707d9bae1/tex2gif-stack-2.gif">[Li₂Li_4/2(NH₂)₂²⁺] show the motif of closest rod packing. They are connected via bromide ions in a distorted cubic primitive arrangement.     

Synthesis and characterization of MCM-48 tubular membranes

MCM-48 membranes have been prepared on alumina supports of different pore sizes. A battery of characterization techniques has been used to study the physical properties and the quality of the membranes prepared. The highest quality membranes were prepared on supports with pore size of up to 60 nm. The MCM-48 membranes were tested in the separation of gas phase mixtures and a cyclohexane/O₂ selectivity higher than 270 was obtained. The selective separation of organic compounds from inert components is a result of the cooperative effects of capillary condensation in MCM-48 pores and of the specific interactions of the permeating compounds and the membrane material.     

Crystal Structures of [Ni(Phen)(i‐Bu2PS2)2] and [Ni(Phen)3](i‐Bu2PS2)2 Complexes and Interaction between Coordinated 1,10‐Phenanthroline Molecules

Single crystals of [Ni(Phen)(it/m4274357627m64h8/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0">Bu₂PS₂)₂] (I) and [Ni(Phen)₃](it/m4274357627m64h8/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0">Bu₂PS₂)₂ (III) compounds were grown, and their structures were determined by Xt/m4274357627m64h8/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0">ray diffraction analysis (CADt/m4274357627m64h8/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0">4 diffractometer, MoK _{t/m4274357627m64h8/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">} radiation, 3336 F _hkl , R = 0.0373 for I and 2575 F _hkl for III). The crystals of complex I have a triclinic unit cell with the following parameters: a = 11.097(1) t/m4274357627m64h8/xxlarge8491.gif" alt="angst" align="MIDDLE" BORDER="0">, b = 14.903(2) t/m4274357627m64h8/xxlarge8491.gif" alt="angst" align="MIDDLE" BORDER="0">, c = 22.650(3)t/m4274357627m64h8/xxlarge8491.gif" alt="angst" align="MIDDLE" BORDER="0">; t/m4274357627m64h8/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0"> = 75.18(1)°, t/m4274357627m64h8/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0"> = 80.50(1)°, t/m4274357627m64h8/xxlarge947.gif" alt="gamma" align="MIDDLE" BORDER="0"> = 75.07(1)°, V = 3479.2(7)t/m4274357627m64h8/xxlarge8491.gif" alt="angst" align="MIDDLE" BORDER="0">³, Z = 4, t/m4274357627m64h8/xxlarge961.gif" alt="rgr" align="MIDDLE" BORDER="0">_calc = 1.255 g/cm³, and space group t/m4274357627m64h8/10947_2004_Article_474369_TeX2GIFIE1.gif" alt=" $$\bar P$$ " align="middle" border="0"> 1; the crystals of III have a monoclinic unit cell with the following parameters: a = 19.010(3)t/m4274357627m64h8/xxlarge8491.gif" alt="angst" align="MIDDLE" BORDER="0">, b = 15.481(1) t/m4274357627m64h8/xxlarge8491.gif" alt="angst" align="MIDDLE" BORDER="0">, c = 17.940(3)t/m4274357627m64h8/xxlarge8491.gif" alt="angst" align="MIDDLE" BORDER="0">; t/m4274357627m64h8/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0"> = 97.58(1)°, V = 5233.5(12)t/m4274357627m64h8/xxlarge8491.gif" alt="angst" align="MIDDLE" BORDER="0">³, Z = 4, t/m4274357627m64h8/xxlarge961.gif" alt="rgr" align="MIDDLE" BORDER="0">_calc = 1.292 g/cm³, and space group C2/c. The structure of complex I is built from mononuclear molecules, and the structure of III, from [Ni(Phen)₃]²⁺ complex cations and it/m4274357627m64h8/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0"> Bu₂PS₂ ^- outert/m4274357627m64h8/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0">sphere anions. The NiN₂S₄ coordination polyhedra in the structure of I and NiN₆ in the structure of III are distorted octahedra. Based on structural data, the interaction between the coordinated Phen molecules of complexes I, [Ni(Phen)₂(it/m4274357627m64h8/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0">Bu₂PS₂)](it/m4274357627m64h8/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0">Bu₂PS₂) (II), and III is considered, as well as the packing modes of these complexes.     

The Influence of Sulfate‐Doping on the Nature of V Sites in VOx/TiO2 Catalysts

EPR, UV/Vis and FTIR spectroscopy as well as thermal analysis (TA/MS) were applied to study the influence of sulfate species present in the anatase support on the specific nature of VO_x species in supported VO_x/TiO₂ catalysts. Those sulfate species modify the local structure of the supported vanadyl species and lead to the formation of two types of VO²⁺ sites instead of only one type being formed on sulfate‐free anatase. EPR and FTIR spectroscopic measurements revealed that a part of the VO²⁺ species are directly bound to the surface sulfate species. By TA/MS it was found that SO₂ is released at lower temperature from VO_x/TiO₂ in comparison to the vanadium‐free support. The direct bonding between sulfate and VO_x species stabilizes the latter on the surface of VO_x/TiO₂ resulting in three effects: 1) a higher V site dispersion in comparison to sulfate‐free TiO₂, 2) a better resistance of surface vanadyls against diffusion into the bulk of the support and 3) a much faster reoxidation of reduced V sites than observed on sulfate‐free TiO₂.     

Hydroarylation of alkynes and alkenes through alumina-sulfuric acid catalyzed regioselective CC bond formation

A highly atom-efficient synthetic protocol for hydroarylation of terminal-aryl alkynes and styrene through the regioselective CC bond formation via the electrophilic addition of naphthols and substituted phenols has been developed using alumina-sulfuric acid as a heterogeneous supported solid acid catalyst. This methodology shows excellent regioselectivity and affords the desired product in good to excellent yield. The heterogeneous catalyst can also be recycled efficiently without much loss of activity.     

NMR chemical shifts in the low–pH form of a-chymotrypsin. A QM/MM and ONIOM–NMR study

 The relationship between hydrogen bonding and NMR chemical shifts in the catalytic triad of low-pH α-chymotrypsin is investigated by combined use of the effective fragment potential [(2001) J Phys Chem A 105:293] and ONIOM–NMR [(2000) Chem Phys Lett 317:589] methods. Our study shows that while the His57 N^δ1−H bond is stretched by a relatively modest amount (to about 1.060 ?) this lengthening, combined with the polarization due to the molecular environment, is sufficient to explain the experimentally observed chemical shifts of 18.2 ppm. Furthermore, the unusual down-field shift of H^ɛ1 (9.2 ppm) observed experimentally is reproduced and shown to be induced by interactions with the C=O group of Ser214 as previously postulated. The free-energy cost of moving H^δ1 from His57 to Asp102 is predicted to be 5.5 kcal/mol. Received: 26 September 2001 / Accepted: 6 September 2002 / Published online: 21 January 2003 Contribution to the Proceedings of the Symposium on Combined QM/MM Methods at the 222nd National Meeting of the American Chemical Society, 2001 Correspondence to: J. H. Jensen e-mail: jan-jensen@uiowa.edu Acknowledgements. This work was supported by a Research Innovation Award from the Research Corporation and a type G starter grant from the Petroleum Research Fund. The calculations were performed on IBM RS/6000 workstations obtained through a CRIF grant from the NSF (CHE-9974502) and on supercomputers at the National Center for Supercomputer Applications at Urbana-Champaign. The authors are indebted to Visvaldas Kairys for help with the CHARMM program, and to Daniel Quinn for many helpful discussions.