bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthese hoch funktionalisierter Organomagnesiumreagentien durch Halogen‐Metall‐Austausch
Authors: Knochel Paul , Dohle Wolfgang , Gommermann Nina , Kneisel Florian F. , Kopp Felix , Korn Tobias , Sapountzis Ioannis , Vu Viet Anh
Published: September 2003

Magnesiumverbindungen spielen eine zentrale Rolle in der präparativen organischen und metallorganischen Chemie. Seit kurzem ermöglicht der Halogen‐Magnesium‐Austausch den Zugang zu einer Reihe funktionalisierter Grignard‐Reagentien. Ester‐, Nitril‐, Iod‐ und Iminfunktionen und sogar Nitrogruppen können in einer breiten Reihe aromatischer und heterocyclischer Organomagnesiumverbindungen vorhanden sein. Auch hoch funktionalisierte Alkenylmagnesiumspezies können auf diese Weise generiert werden. Diese neuen Entwicklungen sowie die Anwendung von Organomagnesiumreagentien in Kreuzkupplungen und Aminierungsreaktionen werden in diesem Aufsatz eingehend beschrieben.
Titelbild: Transformation of a Spherical Supramolecular Dendrimer into a Pyramidal Columnar Supramolecular Dendrimer Mediated by the Fluorophobic Effect (Angew. Chem. 36/2003)
Authors: Percec Virgil , Glodde Martin , Johansson Gary , Balagurusamy Venkatachalapathy S. K. , Heiney Paul A.
Published: September 2003

Der Organisationstyp der (3,4,5)2G2‐CO2Me‐Monodendrone ändert sich, wie im Titelbild gezeigt, von sphärisch nach pyramidal, wenn die aliphatischen durch teilfluorierte Ketten ersetzt werden. Diese Transformation wurde mit einer Kombination von Klein‐ und Weitwinkel‐Röntgenbeugung, Elektronendichterechnungen und Molecular‐Modeling‐Studien untersucht. Näheres dazu findet sich in der Zuschrift von V. Percec et al. auf S. 4474 ff.
Cover Picture: Single‐Wall Carbon Nanotube–Ferrocene Nanohybrids: Observing Intramolecular Electron Transfer in Functionalized SWNTs (Angew. Chem. Int. Ed. 35/2003)
Authors: Guldi Dirk M. , Marcaccio Massimo , Paolucci Demis , Paolucci Francesco , Tagmatarchis Nikos , Tasis Dimitrios , Vázquez Ester , Prato Maurizio
Published: September 2003

Carbon Nanotubes are currently a subject of particular interest in materials chemistry. In the Communication by D. M. Guldi, F. Paolucci, M. Prato, and co‐workers on page 4206 ff., the preparation of a single‐wall nanotube–ferrocene (SWNT–Fc) nanohybrid is described. Photoinduced electron transfer gives rise to a long‐lived charge‐separated state (SWNT.−–Fc.+); the radical anionic form of the nanotube has been detected by laser flash photolysis.
Synthesis and Analgesic and Anti‐inflammatory Activity of Some New (6‐Acyl‐2‐benzoxazolinone and 6‐Acyl‐2‐benzothiazolinone Derivatives with Acetic Acid and Propanoic Acid Residues
Authors: Ünlü Serdar , Önkol Tijen , Dündar Yasemin , Ökçelik Berna , Küpeli Esra , Yeşilada Erdem , Noyanalpan Ningur , Şahin M. Fethi
Published: September 2003

In this study for developing potent analgesic and anti‐inflammatory compounds, we synthesized 6‐acyl‐2‐benzoxazolinone and 6‐acyl‐2‐benzothiazolinone derivatives with acetic acid and propanoic acid side chain, and performed preliminary screening of their in vivo analgesic and anti‐inflammatory activities at a single dose of 100 mg/kg inmice by a p‐benzoquinone‐induced writhing test and a Carrageenaninduced hind paw edema model, respectively. We also determined their gastric ulceration effects in the tested animals. Propanoic acid derivatives were generally found to have higher analgesic and anti‐inflammatory activities, and among them, 3‐(6‐benzoyl‐2‐benzothiazolinon‐3‐yl)propanoic acid (Compound 4 a) exhibited the highest analgesic and anti‐inflammatory activity. However, all compounds showed lower anti‐inflammatory effects than we observed for indomethacin at 10 mg/kg dose. Consequently, 6‐acyl‐2‐benzoxazolinone/2‐benzothiazolinones having propanoic acid side chain might lead to further studies for developing better candidates with potent analgesic and anti‐inflammatory effects while acetic acid derivatives do not exhibit comparable satisfactory features.
Die Pharmazie im Dienste der Propagierung lutherischer Rechtfertigungslehre. Zur Bildaussage eines weitverbreiteten protestantischen Sinnbildmotivs
Authors: Krafft Fritz
Published: September 2003

Pharmacy serving to propagate the Lutherian doctrine of justification: ‚Christus as a pharmacist’︁ is an interconfessional, but confessionally differentiated symbolic motif (Sinnbildmotiv) of Christian folklore art in German‐speaking countries. The article investigates the sociocultural conditions and prerequisites (German bible translation, religion and confession, piety, pharmacy, chymiatry, chemistry, apothecary training and status) for transfering the old metaphor and idea of Christ as a physician to the new vision of Christ as a apothecary who prepares and dispenses his heavenly medicine all by himself. In the early 17th century (especially in the 1610's) these requirements were fulfilled, so that the oldest known witness to this motif transfer (picturing the so‐called Heilandsruf of Matthew 11, 28), a genre picture of 1619, will be the first pictural version of this motif in general. It was created by the protestant Painter Mich(a)el Herr of Nuremberg. In the abstract and reduced form of a devotional picture this motif then became widespread in churches and vicarages, in monasteries and their apothecaries as well as in private houses (with small altars: Herrgottswinkel). The oldest yet known examples are works from around 1630. For the first time during the Thirty Year's War, it served in this form for propagating the Lutherian justification doctrine (now referring to Jesaja 55, 1), saying that the belief in Christ is enough to be released from all sins (sola fide). Around 1650, as a reaction to that, a catholic version of the devotional picture was created, claiming and picturing that in contrast eucharist is the highest and real ‚healing medium’︁ of Christ to redemption. All pictures of this version avoid quoting Jesaja 55, 1, whereas all protestant pictures quote this verse from the Bible word‐for‐word.
Nur „Zweite Wahl”︁ oder Die Berufung Adolf Butenandts zum Direktor des KWI für Biochemie
Authors: Mertens Lothar
Published: September 2003

The remarkable career of the nobel laureate Adolf Butenandt in Germany before 1945 and especially after the second world war is well known. But in recent years several publications have questioned his personal behaviour in the Third Reich. But all these articles interpreted Butenandts career and his attitude from our knowledge today about Nazi Germany. From archival sources this article will view on the situation in the 1930s and will show that Butenandt was originally not the first choice of the government for the position of director at the Kaiser‐Wilhelm‐Institute for Biochemistry. Finally it is shown, that Butenandt did knew what was going on behind the scenes, because through his close connections with officers of the Rockefeller Foundation he got several information on the selection.
Weakly Oriented Liquid‐Crystal NMR Solvents as a General Tool to Determine Relative Configurations
Authors: Aroulanda Christie , Boucard Valérie , Guibé François , Courtieu Jacques , Merlet Denis
Published: September 2003

A new NMR method to determine the relative configuration of asymmetric centres is presented. It proceeds through the use of a weakly ordered solvent and the measurement of orientational order parameters. The method is illustrated by using dihydropyridone derivatives for which the orientations and the relative configurations of the asymmetric carbon atoms are determined unambiguously.
Progressive Studies on the Novel Samarium‐Catalyzed Diastereoselective Tandem Semipinacol Rearrangement/Tishchenko Reduction of Secondaryα‐Hydroxy Epoxides
Authors: Fan Chun‐An , Hu Xiang‐Dong , Tu Yong‐Qiang , Wang Bao‐Min , Song Zhen‐Lei
Published: September 2003

A novel and highly diastereoselective samarium‐catalyzed tandem rearrangement/reduction of secondaryα‐hydroxy epoxides, which involves a C1 to C3 carbon migration rearrangement and a very interesting hetero‐Tishchenko reduction of the intermediate aldehyde and the reductant aldehyde, has been reported. This reaction could be developed to provide a facile and stereoselective construction of 2‐quarternary 1,3‐diol units with an hydroxymethyl moiety attached to the diastereogenic quaternary carbon center. Detailed investigations have been carried out concerning the screening of the aldehydes as a reductant, the optimization of reaction conditions, and the substrate scope of this tandem reaction. A catalytic cycle for this reaction, the electronic and steric effects of the reductant aldehydes, and the mechanism for the acyl migration of 1,3‐diol monoesters are proposed.
Enantioselective Borohydride Reduction Catalyzed by Optically Active Cobalt Complexes
Authors: Yamada Tohru , Nagata Takushi , Sugi Kiyoaki D. , Yorozu Kiyotaka , Ikeno Taketo , Ohtsuka Yuhki , Miyazaki Daichi , Mukaiyama Teruaki
Published: September 2003

The highly enantioselective borohydride reduction of aromatic ketones or imines to the corresponding alcohols was developed in the presence of a catalytic amount of an optically active cobalt(II) complex catalyst. This enantioselective reduction is carried out using a precisely premodified borohydride with alcohols such as tetrahydrofurfuryl alcohol, ethanol and methanol. High optical yields are obtained by choosing the appropriate alcohol as modifiers and a suitable β‐ketoiminato ligand of the catalyst. The enantioselective borohydride reduction has been successfully applied to the preparation of optically active 1,3‐diols, the stereoselective reduction of diacylferrocenes, and dynamic and/or kinetic resolution of 1,3‐dicarbonyl compounds.
Guest–Framework Interaction in Type I Inorganic Clathrates with Promising Thermoelectric Properties: On the Ionic versus Neutral Nature of the Alkaline‐Earth Metal Guest A in A8Ga16Ge30(A=Sr, Ba)
Authors: Gatti Carlo , Bertini Luca , Blake Nick P. , Iversen Bo B.
Published: September 2003

Periodic density functional calculations using pseudopotentials and a local basis set were performed on the type I clathrates A8Ga16Ge30(A=Sr, Ba). Both are known to show promising thermoelectric properties. Ab initio wave functions were analyzed within the framework of the quantum theory of atoms in molecules. This enabled us to analyze both the charge transfer and bonding properties of the clathrate from a rigorous quantum mechanical viewpoint. The Ba and Sr centers were found to be largely ionic (charge: ca. +1.7 e) both in the smaller 20‐atom and in the larger 24‐atom cages, consistent with a Zintl‐phase view of these type I clathrates. The assertion that the Sr atoms in the different cages have similar oxidation states is shown to be consistent with multiwavelength diffraction experiments on Sr8Ga16Ge30; while the assertion of ionicity of the Sr center is supported by the observation that the adsorption edge lies close to that previously found in the Sr K‐edge XANES spectra of Sr(OH)2⋅8 H2O. As such, this work contradicts previous experimental and theoretical studies that claim that the guest atoms are neutral. We show that the discrepancy is related to the definitions used for electron transfer. Definitions based on electron displacement (rearrangement) in space, as in previous works, do not account for the variation in shape and volume of the atomic catchment regions upon change in the number and average locations of the particles in the system. Eventually, such definitions lead to underestimation of charge transfer. The large binding energy found in earlier work for Ba and Sr in these materials is found to be consistent with a simple picture of charge transfer from the guest to the frame. Preliminary investigations on a clathrate of perfect stoichiometry appear to rule out any important relationship between the observed increase in the thermoelectric figure of merit with increasing external pressure and host–guest charge transfer.
Synthesis, Structure and Conformation of Partially‐Modified Retro‐ and Retro‐Inverso ψ[NHCH(CF3)]Gly Peptides
Authors: Volonterio Alessandro , Bellosta Stefano , Bravin Fabio , Bellucci Maria Cristina , Bruché Luca , Colombo Giorgio , Malpezzi Luciana , Mazzini Stefania , Meille Stefano V. , Meli Massimiliano , Ramírez de Arellano Carmen , Zanda Matteo
Published: September 2003

Partially modified retro‐ (PMR) and retro‐inverso (PMRI) ψ[NHCH(CF3)]Gly peptides, a conceptually new class of peptidomimetics, have been synthesized in wide structural diversity and variable length by aza‐Michael reaction of enantiomerically pure α‐amino esters and peptides with enantiomerically and geometrically pure N‐4,4,4‐trifluorocrotonoyl‐oxazolidin‐2‐ones. The factors underlying the observed moderate to good diastereocontrol have been investigated. The conformations of model PMR‐ψ[NHCH(CF3)]Gly tripeptides have been studied in solution by 1H NMR spectroscopy supported by MD calculations, as well as in the solid‐state by X‐ray diffraction. Remarkable stability of turn‐like conformations, comparable to that of parent malonyl‐based retropeptides, was evidenced, as a likely consequence of two main factors: 1) severe torsional restrictions about sp3 bonds in the [CO‐CH2‐CH(CF3)‐NH‐CH(R)‐CO] module, which is biased by the stereoelectronically demanding CF3 group and the R side chain; 2) formation of nine‐membered intramolecularly hydrogen‐bonded rings, which have been clearly detected both in CHCl3 solution and in some crystal structures. The former factor seems to be more important, as turn‐like conformations were found in the solid‐state even in the absence of intramolecular hydrogen bonding. The relative configuration of the ‐C*H(CF3)NHC*H(R)‐ stereogenic centers has a major effect on the stability of the turn‐like conformation, which seems to require a syn stereochemistry. X‐ray diffraction and ab initio computational studies showed that the [‐CH(CF3)NH‐] group can be seen as a sort of hybrid between a peptide bond mimic and a proteolytic transition state analogue, as it combines some of the properties of a peptidyl ‐CONH‐ group (low NH basicity, CH(CF3)‐NH‐CH backbone angle close to 120°, CCF3 bond substantially isopolar with the CO) with some others of the tetrahedral intermediate [‐C(OX)(O−)NH‐] involved in the protease‐mediated hydrolysis reaction of a peptide bond (high electron density on the CF3 group, tetrahedral backbone carbon).
Resonance‐Assisted Intramolecular Chalcogen–Chalcogen Interactions?
Authors: Sanz Pablo , Yáñez Manuel , Mó Otilia
Published: September 2003

High‐level B3LYP/6‐311+G(3df,2p) density functional calculations have been carried out for a series of saturated chalcogenoaldehydes: CH(X)‐CH2‐CH2YH (X, Y=O, S, Se, Te). Our results indicate that in CH(X)‐CH2‐CH2YH (X=Y=O, S, Se) the XH⋅⋅⋅X intramolecular hydrogen bond (IHB) competes in strength with the X⋅⋅⋅XH chalcogen–chalcogen interaction, while the opposite is found for the corresponding tellurium‐containing analogues. For those derivatives in which X≠Y, X being the more electronegative atom, the situation is more complicated due to the existence of two non‐equivalent XH and YH tautomers. The YH tautomer is found to be lower in energy than the XH tautomer, independently of the nature of X and Y. For X=O, S, Se and Y=S, Se the most stable conformerbis the one exhibiting a YH⋅⋅⋅X IHB. Conversely when Y=Te, the chelated conformerd, stabilized through a X⋅⋅⋅YH chalcogen–chalcogen interaction is the global minimum of the potential energy surface. Systematically the IHB and the chalcogen–chalcogen interactions observed for saturated compounds are much weaker than those found for their unsaturated analogues. This result implies that the nonbonding interactions involving chalcogen atoms, mainly Se and Te, are not always strongly stabilizing. This conclusion is in agreement with the fact that intermolecular interactions between Se and Te containing systems with bases bearing dative groups are very weak. We have also shown that these interactions are enhanced for unsaturated compounds, through an increase of the charge delocalization within the system, in a mechanism rather similar to the so call Resonance Assisted Hydrogen Bonds (RAHB). The chalcogen–chalcogen interactions will be also large, due to the enhancement of the X→Y dative bond, if the molecular environment forces the interacting atoms X and Y to be close each other.
Scope, Kinetics, and Mechanistic Aspects of Aerobic Oxidations Catalyzed by Ruthenium Supported on Alumina
Authors: Yamaguchi Kazuya , Mizuno Noritaka
Published: September 2003

The Ru/Al2O3 catalyst was prepared by modification of the preparation of Ru(OH)3⋅n H2O. The present Ru/Al2O3 catalyst has high catalytic activities for the oxidations of activated, nonactivated, and heterocyclic alcohols, diols, and amines at 1 atm of molecular oxygen. Furthermore, the catalyst could be reused seven times without a loss of catalytic activity and selectivity for the oxidation of benzyl alcohol. A catalytic reaction mechanism involving a ruthenium alcoholate species and β‐hydride elimination from the alcoholate has been proposed. The reaction rate has a first‐order dependence on the amount of catalyst, a fractional order on the concentration of benzyl alcohol, and a zero order on the pressure of molecular oxygen. These results and kinetic isotope effects indicate that β‐elimination from the ruthenium alcoholate species is a rate‐determining step.
Supramolecular Spintronic Devices: Spin Transitions and Magnetostructural Correlations in [Fe4IIL4]8+ [2×2]‐Grid‐Type Complexes
Authors: Ruben Mario , Breuning Esther , Lehn Jean‐Marie , Ksenofontov Vadim , Renz Franz , Gütlich Philip , Vaughan Gavin B. M.
Published: September 2003

The magnetism of a series of tetranuclear complexes of the [FeII4L4](X)8 [2×2]‐grid‐type was investigated, revealing the occurrence of spin transition behavior within this class of compounds. The phenomenon depends directly on the nature of the substituent R1 in the 2‐position on the central pyrimidine group of the ligand L. All FeII ions in compounds with R1 substituents favoring strong ligand fields (R1=H; OH) remain completely in the diamagnetic low‐spin state. Only complexes bearing R1 substituents attenuating the ligand field by steric (and to a lesser extent electronic) effects (R1=Me; Ph) exhibit spin transition behavior triggered by temperature. In general, gradual and incomplete transitions without hysteresis were observed for magnetically active complexes. The systems described provide approaches to the development of (supra)molecular spintronics.
Square‐Planar Coordinated Polyanions of Palladium, Platinum, and Gold Stannaborate [SnB11H11]2− Coordination Chemistry
Authors: Marx Thiemo , Mosel Bernd , Pantenburg Ingo , Hagen Siegbert , Schulze Herbert , Wesemann Lars
Published: September 2003

The tetrasubstituted polyanions of platinum, palladium, and gold [M(SnB11H11)4]x− (x=6, M=Pd, Pt; x=5, M=Au) have been prepared and characterized by single‐crystal X‐ray diffraction, elemental analysis, IR, Raman, 11B, and 119Sn heteronuclear NMR spectroscopy. In the case of the platinum derivative [Bu3MeN]6[Pt(SnB11H11)4] (2) 119Sn Mössbauer spectroscopy has been carried out. The isolated salts are stable towards moisture and air and the complexes 2 and 3 were treated with 1,3‐bis(diphenylphosphino)propane (dppp) to give the respective substitution products [Bu3MeN]2[(dppp)M(SnB11H11)2] (M=Pd, Pt).
Gold Catalysis: Efficient Synthesis and Structural Assignment of Jungianol and epi‐Jungianol
Authors: Hashmi A. Stephen K. , Ding Li , Bats Jan W. , Fischer Peter , Frey Wolfgang
Published: September 2003

Starting from 2‐methylfuran and crotonaldehyde, both jungianol and epi‐jungianol were prepared by a six‐step sequence including a gold‐catalyzed arene synthesis and a photochemical SN2‐like reduction with lithium aluminum hydride. Not a single protective group was needed in the entire synthesis. With both diastereomers in hand, the stereochemical assignment in the literature could be corrected by means of a thorough 1H NMR spectroscopic analysis and an X‐ray diffraction study on an epi‐jungianol derivative.
Chiral Pyrimidine Metallacalixarenes: Synthesis, Structure and Host–Guest Chemistry
Authors: Barea Elisa , Navarro Jorge A. R. , Salas Juan M. , Quirós Miguel , Willermann Michael , Lippert Bernhard
Published: September 2003

A set of enantiomerically pure cyclic multinuclear complexes with the formula cis‐[a2PdL]nn+ [a2=(R,R)‐1,2‐diaminocyclohexane (R,R‐dach), (S,S)‐1,2‐diaminocyclohexane (S,S‐dach); n=4, 6; LH=2‐hydroxypyrimidine (2‐Hpymo), 4,6‐dimethyl‐2‐hydroxypyrimidine (2‐Hdmpymo) and 4‐hydroxypyrimidine (4‐Hpymo)] were obtained by reaction of cis‐[a2Pd(H2O)2]2+ and LH in aqueous media. The polynuclear complexes were studied by 1H NMR spectroscopy and X‐ray crystallography. These studies revealed that the N1,N3‐bridging mode exhibited by the pyrimidine moieties is ideally suited for formation of inorganic analogues of calixarenes (metallacalixarenes) in a self‐assembly process. The most stable species are the tetranuclear metallacalix[4]arenes, which are obtained in all cases. Hexanuclear species, namely, [a2Pd(2‐dmpymo)]66+, were also isolated and fully characterised. 1H NMR experiments show conversion of [a2Pd(2‐dmpymo)]66+ to [a2Pd(2‐dmpymo)]44+ on heating. Analogously to organic calixarenes, these systems are also capable of incorporating hard metal ions at the oxo surface. Additionally, investigations on the receptor properties of these metallacalixarenes towards mononucleotides showed that enantioselective recognition processes occur in aqueous media.
Review: Different types of ordering
Authors: Hauck J. , Mika K.
Published: September 2003

Homogeneous structures AxBywith identical A–A or B–B self‐coordination numbersT1,T2,T3, of nearest, next‐nearest and third neighbors are selected. The maximumTivalues are 2 2 2 (1D row), 6 6 6 (2D hexagonal net) and 12 6 24 (3D cubic close‐packing). ReducedT1orT2values for AxBycan be related with attractive or repulsive A–A (or B–B) interactions. A single set ofT1T2T3; y/x values was obtained for y/x = 1–4 and 6. The y/x = 2 structures of three equivalent positions A, B and C are unfavourable for A = ⊕ and B = ⊖ charge or direction of magnetic moments. The spatial distribution of positive and negative potential near A+and B−positions gives rise to neutral C positions. Frustrated magnetic moments at C positions are disordered. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Transmission spectra of crystals at elevated temperatures for the calculation of internal radiant heat transport during crystal growth – Part 1: The spectrometer and its performance
Authors: Schwabe D. , Polity A.
Published: September 2003

We report the construction, operation and performance of a transmission spectrometer for the visible to the IR (up to 3.5 μm wavelength) to measure crystals up to a temperature of 1400 °C. The spectral resolution is almost comparable to that of a commercial spectrometer. The performance of the spectrometer and some problems are demonstrated by spectra of YAG : Nd at different temperatures. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structure and chemical composition of LiB3O5 surfaces
Authors: Atuchin V. V. , Kesler V. G. , Lisova I. A. , Pokrovsky L. D. , Pylneva N. A. , Yurkin A. M.
Published: September 2003

The electronic and structural properties of LiB3O5 (LBO) surfaces have been studied by X‐ray photoemission spectroscopy (XPS) and reflectance high‐energy electron diffraction (RHEED). The as‐grown (110) crystal face and mechanically polished (001) surfaces have been investigated comparatively. Electronic structure of LBO has been determined on as‐grown (110) crystal face previously cleaned by chemical etching with RHEED control. The correlation of valence band structure and measured binding energies with earlier reported results has been discussed. Core‐level spectroscopy reveals strong enriching of mechanically polished LBO surface with carbon, when nanodiamond powder is used as an abrasive. So high carbon level as C:B = 0.7 has been observed at the surface while the ratio Li:B:O remains according to LBO chemical composition. The association of LBO Kikuchi‐lines with strong background has been shown by RHEED analysis of the surface. Thus, the polished LBO surface constitutes a high structure quality LBO with the inclusions of some amorphous carbon compound. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Crystal and molecular structure of 2,6‐bis(4‐chlorophenyl)‐3‐phenylpiperidin‐4‐one
Authors: Ompraba G. , Srinivasan M. , Perumal S. , Sekar K. , Choudhury A. R. , Guru Row T. N. , Rafi Z. A.
Published: September 2003

The crystal structure of the title compound is described. The chemical formula of the compound is C23H19Cl2NO. The compound is found to crystallize in monoclinic system with space group P21/c, Z = 4. The unit cell dimensions are a = 15.137(3) Å, b = 8.9171(18) Å, c = 14.779(3) Å, β = 91.461(4)° and V = 1994.2(7) Å3, Dcalc = 1.320 gcm‐3. The final R factor is 4.4%. The central piperidone ring of the molecule adopts a slightly distorted chair conformation, the mean torsion angle being 52.3°; the phenyl rings are planar. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Toroidal Main Group Macrocycles: New Opportunities for Cation and Anion Coordination
Authors: Doyle Emma L. , Riera Lucía , Wright Dominic S.
Published: September 2003

Inorganic macrocycles, possessing molecular frameworks composed entirely of elements other than carbon, are rare. Even rarer are species analogous to classical organic macrocycles (like crown ethers) that possess the potential ability to coordinate metal ions within their cavities. Recent studies reveal an emerging structural class of valence‐isoelectronic main‐group ligands of general formula [{E(µ‐E′R)}2Y]nx−, which possess fascinating coordination characteristics. Such species can coordinate metal ions within their cavities (using the donor centres Y and E′), their peripheral donor centres (E′) (in an exo fashion) and are also capable of coordinating anions (where Y = N−H). This short review highlights the recent synthetic and structural studies of these unusual ligand systems and pinpoints potential future areas of development. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Monomeric Magnesium and Calcium Complexes Containing the Bidentate, Dianionic 1,2‐Bis[(2,6‐diisopropylphenyl)imino]acenaphthene Ligand
Authors: Fedushkin Igor L. , Skatova Alexandra A. , Chudakova Valentina A. , Fukin Georgy K. , Dechert Sebastian , Schumann Herbert
Published: September 2003

The reduction of 1,2‐bis[(2,6‐diisopropylphenyl)imino]acenaphthene (2,6‐iPr2C6H3‐BIAN) with metallic magnesium or calcium in THF affords the monomeric complexes (2,6‐iPr2C6H3‐BIAN)Mg(THF)3 (1) and (2,6‐iPr2C6H3‐BIAN)Ca(THF)4·(THF)1/2 (2). The crystallisation of 1 and 2 from benzene causes the removal of one of the coordinated THF molecules, yielding (2,6‐iPr2C6H3‐BIAN)Mg(THF)2·(C6H6)1/2 (3a) and (2,6‐iPr2C6H3‐BIAN)Ca(THF)3 (4). Repeated recrystallisation of 1 from benzene gives (2,6‐iPr2C6H3‐BIAN)Mg(THF)2·(C6H6)2 (3b). Although the crystals of 3a and 3b differ in colour and in their crystallographic parameters, their molecular dimensions are very similar. Recrystallisation of 1 from pyridine produces (2,6‐iPr2C6H3‐BIAN)Mg(py)3·(py)2 (5). Complexes 1−5 have been characterised by elemental analysis, UV, IR and 1H NMR spectroscopy, as well as by single‐crystal X‐ray diffraction. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Synthesis and Structure of a Monomeric Chiral Lithium Dialkylaluminium Amide Derived from Schöllkopf’s Bis‐lactim Ether and α‐(Methylbenzyl)benzylamine
Authors: Andrews Philip C. , Maguire Melissa , Pombo‐Villar Esteban
Published: September 2003

Crystals of a monomeric lithium dialkylaluminium amide containing two different chiral amide moieties have been isolated from the reaction of lithiated Schöllkopf’s bis‐lactim ether complexed by pmdta with the diethylaluminium amide of (S)‐α‐(methylbenzyl)benzylamine, with single crystal X‐ray diffraction revealing a migration of the Li cation in the aluminate from its initial position on the pyrazine ring of the lactim ether precursor. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
A Solid‐State, Solution, and Theoretical Structural Study of Kinetic and Thermodynamic Lithiated Derivatives of a Simple Diazomethane and Their Reactivities Towards Aryl Isothiocyanates
Authors: Armstrong David R. , Davies Robert P. , Haigh Robert , Hendy Mark A. , Raithby Paul R. , Snaith Ronald , Wheatley Andrew E. H.
Published: September 2003

(Trimethylsilyl)diazomethane (1‐H) reacts with nBuLi in THF at elevated temperature to afford (previously reported) 1‐Li·3/2THF. However, reaction in hexane/TMEDA at low temperature affords instead the N‐lithiate Me3SiCNNLi·TMEDA (9), which is a novel “open” pseudo‐cubic tetramer in the solid state. Variable‐temperature NMR spectroscopy suggests that N‐metallated 9, apparently the kinetic product of the reaction, irreversibly rearranges at high temperature in solution to give the thermodynamically preferred C‐lithiated isomer. These observations, supported by DFT calculations, influence our understanding of the reactivity of lithiated diazomethanes towards aryl isothiocyanates, suggesting as they do that previously observed product selectivity in these reactions is critically dependent on temperature control exercised during the process. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Sodiated β‐Diphosphonate Carbanions: Characterization of the Tetrameric Cubane and the Hexameric Ladder Complexes [{(iPrO)2P(O)}2CHNa]4and [{(EtO)2P(O)}2CHNa]6
Authors: Nassar Roger , Beatty Alicia M. , Henderson Kenneth W.
Published: September 2003

Reaction of the methylene diphosphonates [(RO)2P(O)]2CH2, where R =iPr or Et, with the metalating reagents NaH,nBuNa or the superbasic mixturetBuONa/nBuLi leads to monodeprotonation, and formation of the complexes [{(iPrO)2P(O)}2CHNa]4(1) and [{(EtO)2P(O)}2CHNa]6(2). Single‐crystal X‐ray diffraction studies revealed that1is tetrameric in the solid state, with a central Na4O4cubane core. Each metal in1is rendered pentacoordinate by binding to three μ3‐O phosphoryl bridges within the cubane, a chelating phosphoryl unit, and also a singleiPrO group. In contrast, the structure of2is hexameric, and is composed of an unusual six‐rung Na6O6ladder core. Three distinct sodium environments as well as μ1‐, μ2‐ and μ3‐O phosphoryl units are present within the ladder framework. No Na−C interactions are present in either1or2. All of the six‐membered NaOPCPO chelate rings display localized P=O double bonds and partial multiple bonding on the P−C−P linkages (mean P−O: 1.49 Å, and mean P−C: 1.69 Å). Ab initio molecular orbital calculations (HF/6−31G*) on model complexes indicate that the hexameric arrangement found for2is thermodynamically more stable than the cubane structure of1, in the absence of steric effects. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Synthesis and Structures of Alkali Metal Amides Derived from the Ligands [N(SiMe2Ph)(SiMe3)]−, [N(tBu)(SiMe3)]−, [N(Ph)(2‐C5H4N)]−, and [N(2‐C5H4N)2]−
Authors: Antolini Floria , Hitchcock Peter B. , Khvostov Alexei V. , Lappert Michael F.
Published: September 2003

The following crystalline complexes are reported: [(M{μ‐N(SiMe2Ph)(SiMe3)})2]n [the cis complex for n = 1 and M = Li (1); and the trans complexes with n = ∞ and M = Na (2), K (4), Rb (5), Cs (6)], [(Na{μ‐trans‐N(SiMe2Ph)(SiMe3)})2(tmeda)] (3), [(K{μ‐trans‐N(tBu)(SiMe3)})4(η‐C6H6)2] (7), [(K{μ‐trans‐N(Ph)(2‐C5H4N)})2(μ′‐thf)3]∞ (8), and [K{μ‐N(2‐C5H4N)2}]∞ (9). Each, except 3, was obtained by metallation of the appropriate secondary amine with LinBu (for 1), MBzl [M = Na (for 2), K (for 4 and 7), Rb (for 5), Cs (for 6)], or KH (for 8 and 9); treatment of 2 with an excess of tmeda yielded 3. Each of 1−9 has an unusual, and in some cases unprecedented, molecular structure. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Synthesis and Characterization of the Very Bulky Phenols Ar*OH and Ar′OH (Ar* = C6H3‐2,6‐Trip2, Trip = C6H2‐2,4,6‐iPr3; Ar′ = C6H3‐2,6‐Dipp2, Dipp = C6H3‐2,6‐iPr2) and Their Lithium and Sodium Derivatives (LiOAr′)2 and (NaOAr*)2
Authors: Stanciu Corneliu , Olmstead Marilyn M. , Phillips Andrew D. , Stender Matthias , Power Philip P.
Published: September 2003

The very bulky phenols Ar*OH (1) and Ar′OH (2), where Ar* = C6H3‐2,6‐Trip2 (Trip = C6H2‐2,4,6‐iPr3) and Ar′ = C6H3‐2,6‐Dipp2 (Dipp = C6H3‐2,6‐iPr2), as well as their lithium and sodium derivatives (LiOAr*)2 (3), (LiOAr′)2 (4) and (NaOAr*)2 (5) have been synthesized and characterized. The terphenols 1 and 2 were obtained by the reaction of the aryllithium reagents with nitrobenzene and were isolated in ca. 70% yield. The lithium or sodium salts 3−5 were isolated by the reaction of 1 or 2 with nBuLi or sodium metal. All compounds were characterized spectroscopically, and by X‐ray crystallography in the case of 1, 2, 4 and 5. The large terphenyl substituents prevent hydrogen‐bonded association of the phenols 1 and 2. Instead, the O−H hydrogens interact with the π‐electron cloud on one of the flanking Trip or Dipp rings. The dimeric structures of 4 and 5 are relatively rare examples of structurally characterized alkali metal phenoxides that are unsolvated by internal electron pair donors or classical Lewis bases such as ethers or amines. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Fluorite‐Related Phases in the System Li‐Pt‐Sn: Synthesis and Structures of Li2PtSn, Li3Pt2Sn3, Li2.27Pt2Sn3.73 and Li2.43Pt2Sn3.57
Authors: Hoffmann Rolf‐Dieter , Wu Zhiyun , Pöttgen Rainer
Published: September 2003

The intermetallic compounds Li2PtSn, Li3Pt2Sn3, Li2.27Pt2Sn3.73 and Li2.43Pt2Sn3.57 were synthesised by reaction of the elements in sealed tantalum tubes. They were investigated by X‐ray diffraction on powders and single crystals: F$\bar 4$
3m, a = 626.0(1) pm, wR2 = 0.0834, 70 F2 values, 7 variables for Li2PtSn; Ia$\bar 3$
, a = 1264.3(1) pm, wR2 = 0.0340, 416 F2 values, 23 variables for Li3Pt2Sn3; Ia$\bar 3$
, a = 1269.7(1) pm, wR2 = 0.1130, 521 F2 values, 24 variables for Li2.27(1)Pt2Sn3.73(1); Ia$\bar 3$
, a = 1266.6(1) pm, wR2 = 0.1094, 620 F2 values, 25 variables for Li2.43(1)Pt2Sn3.57(1). The latter refinement was based on a crystal twinned by merohedry. Li2PtSn crystallises with an ordered variant of the BiF3 type. The other stannides adopt a superstructure of the fluorite type where all three subcell axes are doubled. In Li3Pt2Sn3 the platinum atoms are located on the calcium sites while the tin and 1/3 of the lithium atoms are ordered on the fluorine site. The remaining lithium atoms fill octahedral voids of the fcc arrangement of platinum. The superstructure is discussed on the basis of a group‐subgroup scheme and experimental evidence is given for a solid solution Li3−xPt2Sn3+x. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Synthesis, Structure and Theoretical Studies of the Hydrido Inverse Crown [K2Mg2(NiPr2)4(μ‐H)2·(toluene)2]: a Rare Example of a Molecular Magnesium Hydride with a Mg‐(μ‐H)2‐Mg Double Bridge
Authors: Andrikopoulos Prokopis C. , Armstrong David R. , Kennedy Alan R. , Mulvey Robert E. , O’Hara Charles T. , Rowlings René B.
Published: September 2003

Reaction of benzylpotassium, n,s‐dibutylmagnesium and diisopropylamine in boiling toluene produces a rare example of a molecular magnesium hydride with a Mg‐(μ‐H)2‐Mg double bridge, in [K2Mg2(NiPr2)4(μ‐H)2·(toluene)2] (1). In an effort to rationalise the formation of 1, a series of DFT calculations were performed. This report of 1 establishes the first isostructural pair of Na and K complexes solvated by toluene to be reported in the Cambridge Crystallographic Database. In comparison with its previously reported Na analogue, 2, the metal‐arene centroid distances are considerably shorter (by 0.159 Å) in the new complex reported here. It was found that a hydrocarbon solution of 1 is capable of reducing benzophenone to benzhydrol in moderate yields (74%). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Cover Picture: Structures and Reactions of 1,3‐Diamidodilithium Complexes: the Hemisolvated l‐[CMe2{CHMeN(R)}2Li2·OEt2], the Unsolvated 1:1 Mixed Organo‐amidolithium u‐[CMe2{CHMeN(R′)}2·Li2·(nBuLi)2], and the Product of Oxidative Ring Closure, the Pyrazolidine l‐[(RNCHMe)2CMe2] (R = 2‐iPr‐C6H4; R′ = 2,6‐iPr2‐C6H3) (Eur. J. Inorg. Chem. 18/2003)
Authors: Carey David T. , Mair Francis S. , Pritchard Robin G. , Warren John E. , Woods Rebecca J.
Published: September 2003

The cover picture shows an Li2N2 unit which is prevented by the bulk of the aryl substituents from stacking with another to form a cubic cluster. The diethyl ether solvent traps this fragment of a molecule which, in the absence of diethyl ether, precipitates as a powder, possibly by lateral association of Li2N2 rings to form an infinite ladder in a manner first suggested by Ronald Snaith, whose memory is honoured in this special edition of EurJIC. Details are presented in the article by F. Mair et al. on p. 3464 ff.
Synthesis of Amino Acids with Unnatural Nucleobases or Chromophores Suitable for Use in Model Electron‐Transfer Studies
Authors: Wagner Thomas , Davis William B. , Lorenz Katrin B. , Michel‐Beyerle Maria E. , Diederichsen Ulf
Published: September 2003

We describe the syntheses of Boc‐protected amino acids bearing the chromophores pyromellitic diimide, naphthalene diimide, and pyrene in their side chains, as well as nucleo amino acids with the artificial purines 7‐carbaguanine, 7‐carbaadenine, isoadenine, and 7‐carbaisoadenine covalently linked to the alanyl side chain. These amino acids incorporating chromophores are suitable building blocks for incorporation into alanyl‐PNA for future investigations of the mechanism of nucleobase‐mediated electron transfer. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Synthesis of New Hexosaminyl D‐ and L‐chiro‐Inositols Related to Putative Insulin Mediators
Authors: Cid M. Belén , Bonilla Julia B. , Alfonso Francisco , Martín‐Lomas Manuel
Published: September 2003

We have developed an efficient synthetic strategy to HexNH2‐α(1⇄3)‐L‐chiro‐inositol (XII−XIII) and HexNH2‐α(1⇄2)‐D‐chiro‐inositol (XIV−XV) based on the regio and stereoselective glycosylation of tetrabenzoyl‐L‐chiro‐inositol 2 and tetrabenzyl‐D‐chiro‐inositol 14. Compounds XII−XV may constitute the central structural motifs of inositolphosphoglycans, which have been proposed as putative insulin mediators, and their syntheses have been designed on the basis of biosynthetic considerations. The syntheses of XII−XIII and XIV−XV involve the selective monoglycosylation of an L‐chiro inositol diequatorial diol system (2) and a D‐chiro inositol axial/equatorial diol system (14), respectively. To establish the experimental conditions to achieve the best reactivity−selectivity balance, the glycosylation reactions were studied using D‐gluco‐ and D‐galacto‐configured 2‐azido‐2‐deoxytrichloacetimidate glycosyl donors with different reactivities. The results obtained provide a practical synthetic route and new reactivity−selectivity data. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Efficient Preparation of Three Building Blocks for the Synthesis of Heparan Sulfate Fragments: Towards the Combinatorial Synthesis of Oligosaccharides from Hypervariable Regions
Authors: Gavard Ollivier , Hersant Yaël , Alais Jocelyne , Duverger Véronique , Dilhas Anna , Bascou Alison , Bonnaffé David
Published: September 2003

New, multigram routes to suitably protected L‐iduronyl monosaccharide donors 4 and 5 and 2‐azidoglucose acceptors 6 and 7 are described. The L‐iduronyl and D‐glucuronyl disaccharides 1−3 were then prepared from these compounds, by means of efficient and regioselective protective group manipulations. These disaccharides form the basis of a combinatorial approach toward the synthesis of heparan sulfate fragments representative of the heterogeneous regions of this polysaccharide. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)Introduction
Dimethylzinc‐Promoted Vinylation of Nitrones with Vinylboronic Esters of Pinacol: A New Route toN‐Allylic Hydroxylamines
Authors: Pandya Shashi U. , Pinet Sandra , Chavant Pierre Y. , Vallée Yannick
Published: September 2003

Activation of vinylboronic esters of pinacol (alkenyl‐4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolanes) with dimethylzinc allows nucleophilic addition of the vinyl group onto nitrones, producingN‐allylic hydroxylamines in excellent yields. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Synthesis and Conformational Studies of Methylated, Highly Branched Fluoroolefins: Gear‐Meshed Conformational Isomers
Authors: Nishida Masakazu , Fukaya Haruhiko , Ono Taizo
Published: September 2003

Methylated, highly branched fluoroolefins were prepared by treatment of hexafluoropropene trimers with CH3Li and CH3MgBr. Their structures, which included some rotational isomers, were determined by NMR and GC‐MS and were further confirmed by B3LYP‐GIAO calculation of NMR shieldings. Of the seven methylated fluoroolefins isolated in pure states, three were shown to be mixtures of pairs of conformational isomers. The methylated fluoroolefins containing two bulky geminal substituents such as (CF3)2CF and (CF3)2CCH3 showed gear‐meshed conformations in which the two bulky substituents were conformationally locked. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Synthesis of β‐D‐Galp‐(1⇄4)‐β‐D‐GlcpNAc‐(1⇄2)‐α‐D‐Manp‐(1⇄O)(CH2)7CH3 Mimics to Explore the Substrate Specificity of Sialyltransferases and trans‐Sialidases
Authors: Joosten John A. F. , Evers Britta , Summeren Ruben P. van , Kamerling Johannis P. , Vliegenthart Johannes F. G.
Published: September 2003

Eleven trisaccharide octyl glycosides related to the N‐glycan sequence β‐D‐Galp‐(1⇄4)‐β‐D‐GlcpNAc‐(1⇄2)‐α‐D‐Manp‐(1⇄O)(CH2)7CH3 (1) designed for detailed exploration of the acceptor specificity of α‐2,3‐ and α‐2,6‐sialyltransferases as well as trans‐sialidases, have been synthesised: β‐D‐Galp‐(1⇄4)‐β‐D‐GlcpNPr‐(1⇄2)‐α‐D‐Manp‐(1⇄O)(CH2)7CH3 (2), β‐D‐Fucp‐(1⇄4)‐β‐D‐GlcpNR‐(1⇄2)‐α‐D‐Manp‐(1⇄O)(CH2)7CH3 (3, R = Ac; 4, R = Pr), 6‐amino‐6‐deoxy‐β‐D‐Galp‐(1⇄4)‐β‐D‐GlcpNR‐(1⇄2)‐α‐D‐Manp‐(1⇄O)(CH2)7CH3 (5, R = Ac; 6, R = Pr), 2‐deoxy‐β‐D‐Galp‐(1⇄4)‐β‐D‐GlcpNR‐(1⇄2)‐α‐D‐Manp‐(1⇄O)(CH2)7CH3 (7, R = Ac; 8, R = Pr), βD‐GalpNR1‐(1⇄4)‐β‐D‐GlcpNR‐(1⇄2)‐α‐D‐Manp‐(1⇄O)(CH2)7CH3 (9, R = R1 = Ac; 10, R = R1 = Pr; 11, R = Ac, R1 = Pr; 12, R = Pr, R1 = Ac). All trisaccharides were obtained by condensation of suitably modified glycosyl donors based on imidates or thioglycosides with the single disaccharide acceptor octyl (3,6‐di‐O‐benzyl‐2‐deoxy‐2‐phthalimido‐β‐Dglucopyranosyl)‐(1⇄2)‐3,4,6‐tri‐O‐benzyl‐α‐D‐mannopyranoside, followed by deprotection. For the trisaccharides containing an N‐acylated glucosamine as well as an N‐acylated galactosamine unit, use was made of a combination of N‐phthaloyl and N‐dimethylmaleoyl protection. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Processing of composite industrial effluent by reverse osmosis
Authors: Sridhar Sundergopal , Prasad K Krishna , Murthy G Suryanarayana , Rao A Gangagni , Khan Asad Ali
Published: September 2003

Reverse osmosis (RO) is a well‐established process for water desalination and effluent treatment and it is anticipated that its application could be extended to complex mixtures of industrial effluents. Pilot‐scale experiments using a spiral‐wound thin‐film composite (TFC) polyamide membrane were carried out to investigate the potential of RO for processing a composite effluent, which was a mixture of various wastewaters from bulk drug and pharmaceutical factories. Separation performance was evaluated at various feed pressures (0–70 bar) and feed concentrations (2–30 gdm−3), and was found to improve with increasing pressure. High rejection of dissolved solids (∼98%), COD, BOD and almost complete removal of color were achieved with reasonable flux rates and water recovery. The effect of concentration polarization and fouling on flux and rejection rates as functions of time was evaluated. An approximate cost estimate for an aerobic process vis‐à‐vis a RO membrane process for treatment of the composite effluent is presented. Copyright © 2003 Society of Chemical Industry
Removal of cadmium from dilute aqueous solutions with a rotating cylinder electrode of expanded metal
Authors: Grau Javier M , Bisang José M
Published: September 2003

The removal of cadmium from dilute solutions using a continuous undivided electrochemical reactor with a rotating cylinder cathode of expanded metal is analysed. The effects of cathodic applied potential, size and orientation of expanded metal meshes and inlet cadmium concentration were ascertained. The results show that cadmium can be removed from dilute solutions (inlet concentration range 5–50 mg dm−3) with a high fractional conversion of between 35 and 40% depending on the operating conditions. Thus a minimal residual cadmium concentration of 3 mg dm−3 was achieved. The specific energy consumption increases from 0.6 to 2 kWh mol−1 as the cadmium concentration decreases. Copyright © 2003 Society of Chemical Industry
Anaerobic degradation of polyethylene glycol mixtures
Authors: Otal Emilia , Lebrato Julian
Published: September 2003

Anaerobic treatment of polyethylene glycol may represent an alternative to integrated chemical–biological treatment for the elimination of polyethylene glycol. Anaerobic biodegradation of synthetic waters are made with a mix of polyethylene glycol of molecular weights 400, 600 and 1000 and another made with polyethylene glycol of molecular weights 1500, 3000 and 10 000, was studied using an inoculum adapted to polyethylene glycol 10 000. The critical and minimum retention times were estimated and ranged from 13.2 to 14 and from 18 to 20 days, respectively. Under these operational conditions, the removal percentage ranged from 85 to 90%. Thus, anaerobic degradation of synthetic water containing polyethylene glycol produces removal percentages and hydraulic retention times similar to those of biodegradable wastewater tested at the same operational conditions. Copyright © 2003 Society of Chemical Industry
RDX biodegradation column study: influence of ubiquitous electron acceptors on anaerobic biotransformation of RDX
Authors: Wani Altaf H , Davis Jeffrey L
Published: September 2003

A series of column studies, with aquifer material from the former Nebraska Ordinance Plant (NOP), were performed to explore the phenomenon of electron competition from ubiquitous inorganic electron acceptors (nitrate and sulfate) present in contaminated groundwater. Acetate was used as a source of readily biodegradable carbon in all of the treatment‐column systems. Influent hexahydro‐1, 3, 5‐trinitro‐1, 3, 5‐triazine (RDX) concentrations (1–1.8 mg dm−3) were completely removed to below detection levels of 20 µg dm−3 in all treatment‐column systems without any nitroso‐metabolites. In the control‐column system (with no carbon amendment) significant levels (∼30% of the inlet molar RDX) of nitroso‐substituted RDX derivates were observed in the effluent stream. The estimated first‐order biodegradation rate coefficient for RDX was highest (0.79 h−1) in the treatment‐column system where acetate was the only amendment, about 52 times higher than the rate coefficient (0.015 h−1) obtained in the control‐column system. The presence of sulfate (100 mg dm−3) in influent groundwater temporarily delayed the onset of RDX biotransformation without any adverse effects on overall RDX biotransformation. Coexistence of low (100 mg dm−3) nitrate levels in the influent feed water reduced the first‐order biodegradation rate coefficient obtained in the absence of nitrate by about 80% to 0.16 h−1. These nitrate levels, however, were low to halt the RDX biodegradation probably because the available carbon levels were high enough to exceed the demands for nitrate reduction. High levels of nitrate (500 mg dm−3) initially halted RDX removal, and significantly reduced the rate of RDX biotransformation by about 98% to 0.02 h−1, thereby increasing the half‐life from 0.9 h in the absence of nitrate to about 32 h, with noticeable levels of untreated RDX in the effluent stream. Contrary to the expectations, the presence of ammonium in conjunction with acetate resulted in a lower (0.09 h−1) biodegradation rate coefficient as compared with the one obtained in the absence of ammonium. Copyright © 2003 Society of Chemical Industry