bluuebunny/crossref_metadata_2025 huggingface dataset:
Corrosion fatigue behaviour of nitrogen‐implanted steel in water
Authors: De Anna P. L. , Cerisola G. , Bonora P. L. , Lo Russo S. , Mazzoldi P. , Scotoni I. , Tosello C.
Published: May 2005

The corrosion fatigue behaviour of nitrogen implanted iron in neutral solutions has been investigated utilizing the oscillating cantilever beam method, by means of electrochemical (Ecorr vs. time plots, Rp measurements) and S. E. M. techniques.

The calculated corrosion rate under stagnant conditions is lowered for the implanted iron at all nitrogen doses with respect to untreated iron. The surface oxide layers achieve enhanced protecting capacity.

Consequently under a cyclic load of 25.4 kg mm−2, at a frequency of 16.6 Hz, cracks nucleation is delayed. The time to breaking of implanted specimens is considerably lower in our experimental conditions compared to untreated iron. The increase in the crack growth rate is consistent with the detrimental action of structural damage following implantation. The fracture morphology is also discussed.
Titan: Moderner Werkstoff des Chemieapparatebaus – Ein Beitrag zur Schadenskunde
Authors: Protogerakis Emmanuil , Steiger Klaus
Published: May 2005

Im Chemieapparatebau wird Titan in den letzten Jahren aufgrund seiner hohen Korrosionsbeständigkeit und seines günstigen Preis/Gewicht‐Verhältnisses häufiger angewendet.

Titan besitzt eine hervorragende Beständigkeit in einer Reihe von kritischen Medien, wie z.B. wäßrigen Chloridlösungen, salpetersauren Lösungen, Chromsäure, schwefeliger Säure und feuchtem Chlorgas. Völlig unbeständig ist Titan in fluoridhaltigen Angriffsmitteln, in trockenem Chlorgas, in roter rauchender Salpetersäure, in Salzsäure sowie in salzsaurem Methanol. In den letztgenannten Lösungen erleidet Titan Spannungsrißkorrosion, falls ausreichend hohe Zugspannungen vorliegen. Seine hohe Korrosionsbeständigkeit verdankt Titan einer oxidischen Deckschicht, die das an sich sehr unedle Metall von der aggressiven Umgebung trennt. Eine Verletzung der Schutzschicht, wie dies z.B. in strömenden Angriffsmitteln häufiger beobachtet wird, kann zu einem beschleunigten Angriff auf den Ti‐Werkstoff führen. In der vorliegenden Arbeit werden als Beitrag zur Schadenskunde an Hand einiger Beispiele typische Schadensfälle aufgezeigt, die im Laufe der Jahre aufgetreten sind.
CORIS®: Korrosionsdatenbank
Authors: Gervens Th. , Krohn‐Huppertz R. , Schlagner W.
Published: May 2005

In der vorliegenden Arbeit wird die Kernkomponente des Systems CORIS, die Korrosionsdatenbank, vorgestellt. In ihr sind Korrosionsfakten unter Berücksichtigung aller relevanten Parameter abgelegt. Es wird die dem System zugrunde liegende Korrosionsstruktur mit Hilfe von E/R‐Modellen (Entity‐Relationship‐Modelle) erläutert und ein detaillierter Einblick in die Funktionalität und das Erscheinungsbild gegeben. Das System bietet dem Anwender die Möglichkeit, sowohl eigene Korrosionserfahrungen abzulegen als auch unter Eingabe von Suchbedingungen vorhandenes Wissen zu recherchieren. Die graphisch interaktive Benutzeroberfläche ist auch für ungeübte DV‐Nutzer leicht zu bedienen.
Die Versorgung von CORIS® mit Stoffdaten
Authors: Eckermann R. , Sass R.
Published: May 2005

Im folgenden wird die Stoffdatenbank als Komponente des Korrosionsinformationssystems CORIS vorgestellt. In ihr sind die thermophysikalischen Eigenschaften der in CORIS verwendeten Medien abgespeichert. Die zugrunde liegende Struktur wird erläutert und ein Einblick in die Funktionalität gegeben. Das System erlaubt die Recherche gespeicherter und die Eingabe eigener Werte. Die allen CORIS‐Komponenten gemeinsame graphisch‐interaktive Windows‐Oberfläche ermöglicht eine von Systemsprachen unabhängige äußerst einfache Bedienung des Systems.
Ein Expertensystem zur Auswahl von Werkstoffen für schwefelsaure Medien in CORIS®
Authors: Hatzinasios A.
Published: May 2005

Das Verhalten von Werkstoffen in schwefelsauren Medien wurde mit der Shell‐NEXPERT‐OBJECT entwickelt. Das System enthält etwa 1200 Regeln und 250 Werkstoffe, die aus der DECHEMA‐Werkstoff‐Tabelle und durch Akquisition von Korrosionsexperten stammen. Über die graphische Benutzeroberfläche kann der Benutzer zwischen Werkstoffauswahl, Schadensanalyse und Werkstoffüberprüfung wählen.

Ergebnis: Der Benutzer erhält geeignete Werkstoffe für sein Problem und zusätzlich tendenzielle Aussagen über deren Verhalten in bezug auf andere Korrosionsarten.
Hochtemperaturkorrosion hochlegierter Stähle unter simulierten Müllverbrennungsbedingungen
Authors: Spiegel M. , Grabke H. J.
Published: May 2005

Das Korrosionsverhalten hochlegierter Stähle wurde in Auslagerungsexperimenten in N2‐O2‐HCl‐SO2‐Atmosphären bei 600°C mit und ohne Ablagerungen aus der Müllverbrennung untersucht. Zusätze von 500–3000 vppm HCl zur N2‐O2‐Atmosphäre bewirken immer beschleunigte Korrosion. Dabei entsteht Chlor, welches durch Risse und Poren. des Oxids zur Phasengrenze Metall/Oxid diffundiert und hier überwiegend FeCl2 bildet; verdampft und wird bei Auswärtsdiffusion durch die Oxidschicht zu Fe2O3 oxidiert („aktive Oxidation”︁). Die Korrosion wird nach Zugabe von SO2 durch Sulfidbildung auf dem Metallchlorid stark herabgesetzt. Bei 600°C kommt es unter Ablagerungen zur „Hot Corrosion”︁ durch eine Sulfatschmelze. In N2‐O2 werden die Oxidschichten durch basischen Aufschluß gelöst. dabei bilden sich PbCrO4 und zinkreicher Spinell. In N2‐O2‐SO2 werden die Oxidschichten durch sauren Aufschluß als Sulfate gelöst, unter diesen Bedingungen verhalten sich Cr2O3‐Deckschichten hinreichend resistent. In N2‐O2‐HCl kommt es zur Bildung von (K. Na) Cl in den Ablagerungen und damit zur katastrophalen Korrosion durch Chlor. Die Zugabe von SO2 zu N2‐O2‐HCl‐bewirkt eine Verringerung der Chlor‐Korrosion und saures Verhalten der Schmelzen.
Corrosion behaviour of various steels and alloys in a simulated coal liquefaction environment
Authors: Fujikawa H. , Shida Y.
Published: May 2005

The corrosion behaviour of Fe‐Cr, Ni‐Cr and Fe‐Cr‐Ni alloys was studied in simulated liquefaction environments over the temperature range of 623 to 723 K. Corrosion of alloys in these environments was controlled by both sulfidation and oxidation. In the slurry, the oxygen potential was apparently higher and the corrosion rate was smaller in comparison with those in the gas phase in the solvent only environment. An oxygen‐rich brown coal caused much smaller corrosion than a sub‐bituminous coal. With regard to the effect of the alloy compositions, chromium content controlled the corrosion rate. The Fe‐Cr‐Ni austenitic alloys were the most resistant. The Fe‐Cr alloys with high chromium content were fairly resistant, although they may be relatively sensitive to the variation of the environments such as temperature and H2S content. Ni‐Cr alloys of less than 20% Cr may have high corrosion rate due to their fast sulfidation. The structure of the scales formed on the alloys can be reasonably explained by the phase stability diagram of Metal‐O‐S system.
Untersuchung der Korrosionsbeständigkeit von Auftragschweißungen der Hartlegierungsfülldrahtelektroden Stelly Fe12 und Stelloy 6
Authors: Garz I. , Boese E. , Hubold K. , Weber F.
Published: May 2005

Panzerungen aus Cobaltbasislegierungen (Stellite) werden vielfach für den Einsatz unter kombinierter Korrosions‐ und Verschleißbeanspruchung bei höheren Temperaturen verwendet. Für Einbauten in Kernreaktoren sind jedoch cobaltfreie Überzüge erforderlich, um eine möglichst niedrige Strahlenbelastung zu erreichen. Darüber hinaus besteht aus Kostengründen ein allgemeines Interesse der Armaturenindustrie an cobaltfreien Schweißzusatzwerkstoffen. Das Problem bei der Entwicklung cobaltfreier Ersatzlegierungen besteht darin, daß diese eine ebenbürtige Verschleiß‐ und Korrosionsbeständigkeit aufweisen müssen.

Es wurden Auftragschweißungen der niobhaltigen Fülldrahtelektrode Stelloy Fe12 mit ca. 19% Cr und 10% Ni hinsichtlich ihrer Beständigkeit in 0,5 M Schwefelsäure bei 66°C sowie gegenüber interkristalliner Korrosion (IK) im Vergleich zur Cobaltbasislegierung Stelloy 6 untersucht.

Die im Dauertauchversuch ermittelte Beständigkeit in Schwefelsäure war nicht zufriedenstellend. Dagegen erwiesen sich beide Elektroden bzw. Auftragschweißungen im EPR‐Verfahren als IK‐beständig. Nachteilig auf die Beurteilung wirkt sich die hohe Matrixauflöung an geschliffenen Proben aus.
The role of mass spectrometry in vitamin D research
Authors: Yeung Bernice , Vouros Paul
Published: May 2005

1,25‐dihydroxyvitamin D3 is the active metabolite of vitamin D3, and has been found to play important roles in mineral balance and immunological regulation. Recently, 1,25‐dihydroxyvitamin D3 and similar synthetic analogs in development have been found to possess potential therapeutic values in the treatment of proliferative diseases, including leukemia, breast cancer, and psoriasis. Current methods for the analysis of these compounds may either lack the necessary sensitivity (i.e., UV detection) or specificity (i.e., receptor binding assay). In addition, the synthetic analogs developed to date have not been found to uniformly bind with receptors in binding assays, a property that may render them to be difficult for measurement at the trace levels. Methods utilizing mass spectrometry (MS) have been used for either structural identification or quantification. Electron impact ionization has been the technique of choice for structural analysis, whereas newer ionization techniques have been utilized for the quantification of metabolites, often in conjunction with on‐line separation. In this review, MS and non‐MS based methods for vitamin D analysis will be discussed, with an emphasis on the former. Historical perspectives, the present state, and the future role of MS in vitamin D research will be discussed. © 1996 John Wiley & Sons, Inc.
Multiply charged ions
Authors: Vékey Károly
Published: May 2005

Formation, characteristics of, and applications using doubly and multiply charged ions are reviewed in the present article. The main emphasis is on medium‐ to large‐sized molecules, from the point‐of‐view of organic, physico‐organic, and bio‐organic mass spectrometry. Multiply charged species can be studied by all conventional mass spectrometric techniques. Those techniques and reaction types that are particularly relevant to multiply charged ions are discussed in some detail in Section III. Studies on small‐ to medium‐sized molecules are discussed in Section IV. A particularly interesting aspect, the distinction of doubly charged isomeric ions, is also treated here. Multiply charged ions of large (bio‐)molecules are discussed in Section V. This area is fast expanding, mainly due to the spread of electrospray ionization. Fragmentation and conformation of multiply protonated peptides is discussed in detail. © 1996 John Wiley & Sons, Inc.
Soft‐ionization mass spectrometry study of deoxynucleoside bioclusters and deoxynucleoside‐antitumor medicinal preparation clusters
Authors: Sukhodub Leonid F.
Published: May 2005

This article reviews the results of mass spectrometric investigations of the formation mechanism and the energy stabilty of the bioclusters DNA and RNA nucleotide pairs, and nucleoitde base clusters containing certain antitumor medicinal preparations. All of the results discussed were obtained using temperature‐dependent field ionization mass spectrometry (TD‐FIMS) and well‐known and approved desorption mass spectrometry techniques; e.g., fast atom bombardment (FAB) and plasma‐desorption mass spectrometry (PDMS).

A variety of data are presented on the formation enthalpies of Watson–Crick (Hoogsteen) and other H‐bonded base‐pairs, nucleobase stacking dimers, base hydrates, and their complementary pairs in vacuum. Analysis of the data permitted a thermodynamic stability sequence of bioclusters under study to be constructed. The nucleobases in rare (enol and imine) tautomer forms are shown to produce H‐bonded pairs comparable in energy with the canonical A · T pair.

This review summarizes the results of recent investigations into the interactions of DNA, nucleosides, bases, and some amino acids with antitumor preparations such as triethylene thiophosphate amide (thio TEPA), prospydine (Psp), farmorubicin (Far), and doxorubicin (Dox). The specific features of the Dox and Far clusters formation observed in the mass spectra are found to correlate with the antitumor chemotherapeutic activity of these antibiotics. © 1996 John Wiley & Sons, Inc.
Particle‐induced desorption in mass spectrometry. Part II. Effects and applications
Authors: Demirev Plamen A.
Published: May 2005

In the second part of this review (see preceding article for Part I), desorption‐induced processes by polyatomic projectiles over a broad energy range is described. The nonlinear increase in secondary ion yields as a function of the number of constituent atoms, which is evidence for “collective” effects, is discussed. Effects accompanying ion ejection upon monotornic or polyatomic particle impact, namely secondary electron emission, impact‐induced luminescence (photon emission), and sputtering of clusters (fullerenes in particular) by energetic ions, are intimately related to the mechanisms of desorption, and for that reason are also reviewed. Some of these phenomena, linked to, e.g., methods of ion detection, have (or may have in the future) practical applications in analytical mass spectrometry. In conclusion, selected examples for useful analytical applications of desorption methods like PDMS and FAB mainly in the biochemical field, which may illustrate current and emerging trends and perspectives, are discussed. © 1996 John Wiley & Sons, Inc.
Application of secondary ion and matrix‐assisted laser desorption‐ionization time‐of‐flight mass spectrometry for the quantitative analysis of biological molecules
Authors: Muddiman David C. , Gusev Arkady I. , Hercules David M.
Published: May 2005

This review primarily focuses on the current status of two solid‐state mass spectrometric (MS) techniques, namely, static secondary‐ion (SIMS) and matrix‐assisted laser desorption‐ionization (MALDI) time‐of‐fight (TOF) maSs spectrometry, as applied to the quantification of biological materials. Although a number of articles have appeared in the literature for both SIMS and MALDI quantitative analysis, neither field has been extensively researched nor currently used in general practice. However, several results are very exciting and offer advantages over conventional methods. The abilities and limitations of MALDI and SIMS for quantitative analysis of biological molecules will be discussed at the fundamental and applied level. Use of an internal standard approach, development of instrumental protocols, and sample preparation will be examined in detail. Various examples demonstrating the feasibility of quantitative analysis by MALDI and SIMS, including quantification of in vivo and in vitro metabolism of drugs in real biological matrices, will be reviewed. © 1996 John Wiley & Sons, Inc.
Neue Entwicklungen auf dem Gebiet der Schweißtechnik
Authors: Steffens H.‐D. , Klingauf S.
Published: May 2005

Im vorliegenden Beitrag sind anhand von ausgewählten Beispielen neue Entwicklungen auf einigen Gebieten der Schweißtechnik beschrieben. Diese Entwicklung wird durch wirtschaftliche Gesichtspunkte wesentlich beschleunigt und ist noch nicht an ihrem Ende angelangt.
Formulierung des in Grundversuchen ermittelten zeitabhängigen Spannung‐Dehnung‐Verhaltens viskoelastischer Werkstoffe
Authors: Schlimmer M.
Published: May 2005

Unter der Voraussetzung der Existenz einer mechanischen Zustandsgleichung werden Rechenverfahren untersucht, mit denen das in Grundversuchen ermittelte mechanische Verhalten viskoelastischer Werkstoffe unabhängig von der Beanspruchungsart beschrieben werden kann. Als Beispiel kann die Bestimmung des Kriechverhaltens aus Zugversuchen mit konstanter Dehngeschwindigkeit genommen werden. Ausgehend von der üblichen doppellogarithmischen Darstellung der Ergebnisse aus Kriechversuchen mit jeweils konstanter Spannung und/oder Zugversuchen wird eine mechanische Zustandsgleichung aufgestellt. Die Ergebnisse der Anwendung dieser Gleichung zur Beschreibung des Werkstoffverhaltens unter konstanter Dehngeschwindigkeit, Kriech‐ und Relaxationsbedingungen in Grundversuchen sind mit dem zeitabhängigen Verhalten von Polycarbonat verglichen.
Einführung in die Grundlagen der Bruchmechanik Teil 3:. Das Ermüdungsrißwachstum in bruchmechanischer Darstellung
Authors: Dander W.
Published: May 2005

Im folgenden soll das Ermüdungsrißwachstum in der bruchmechanischen Darstellungsweise erläutert werden, wobei eine Beziehung zwischen der Wöhler‐Kurve (klassischer Ermüdungsversuch) und dem bruchmechanischen Ermüdungsversuch hergestellt wird, sowie einige für die Ingenieurpraxis interessante Aspekte erläutert werden.
Das Verhalten von galvanisch verzinktem unlegiertem Vergütungsstahl bei schwingender und stoßartiger Beanspruchung
Authors: Apel B. , Marrek K.‐H. , Prang W.
Published: May 2005

Durch leicht reproduzierbare Untersuchungen wird nachgewiesen, daß der beim galvanischen Verzinken evtl. von der Probenoberfläche aufgenommene diffusible Wasserstoff ‐ hier absichtlich neben dem Zink kathodisch mit abgeschieden ‐ nur in einer begrenzten Zeitspanne vom Ende der Oberflächenbehandlung an gerechnet, das Bauteilverhalten bei dynamischer und stoßartiger Beanspruchung beeinflußt. Der normalgeglühte Gefügezustand wird in seinem Versprödungsverhalten mit einem schlecht vergüteten d. h. eigenspannungsbehafteten Material verglichen.
Untersuchungen zur Initiierung interkristalliner Schwingungsrisse in interstitiell freien (IF‐) Stählen
Authors: Kocik R. , Pries H. , Finke M. , Hagemann J. , Eisenberg S.
Published: May 2005

Bei Untersuchungen zur Ermüdungsfestigkeit interstitiell freier Stähle sind mit dem Auftreten interkristalliner Schwingungsrisse erstmals Schadensmechanismen aufgetreten, die den Einsatzbereich dieses für seine hervorragenden mechanischen Eigenschaften bekannten Werkstoffes erheblich begrenzen können. In metallographischen Untersuchungen konnten die für dieses Schadensbild bekannten Ursachen wie die Bildung von schalenförmigem Tertiärzementit oder die Schwächung der Korngrenzen durch Ausscheidungen ausgeschlossen werden. Im vorliegenden Beitrag werden Untersuchungsergebnisse mit hochauflösenden elektronenoptischen Analyseverfahren (TEN, AES) vorgestellt.
Untersuchungen zum Schweißen der aushärtbaren Aluminiumlegierungen AlMgSi 1 und AlCuMg 1 mit einem gepulsten Festkörperlaser
Authors: Beek I. , Weisheit A. , Mordike B. L.
Published: May 2005

In dieser Arbeit werden Ergebnisse zum Schweißen der aushärtbaren Aluminiumiumlegierungen AlMgSi 1 und AlCuMg 1 mittels eines gepulsten 1.2 kW Nd: YAG‐Lasers ohne Zusatzwerkstoff vorgestellt. Gefügt wurden 1 mm starke Bleche im I‐Stoß. Bei einer Spaltbreite von 50 μm sind Nähte mit nur geringem Durchhang realisierbar. Der geringe Strahldurchmesser (ca. 0.2mm im Fokus) führt zu sehr schmalen Nähten und Wärmeeinflußzonen. Der hohe Temperaturgradient im Schmelzbad führt zudem zu einer Kornfeinung im Schweißgut und nur zu geringfügigen Korngrenzanschmelzungen in der kritischen Übergangszone zwischen Schweißgut und Wärmeeinflußzone. Wird im ausgehärteten Zustand geschweißt, sinkt die Härte im Schweißgut auf das Niveau des lösungsgeglühten Zustandes ab. Da keine signifikante Verdampfung oder Oxidation von Legierungselementen auftritt, kann durch eine nachfolgende vollständige Aushärtungsbehandlung die max. Härte wieder erreicht werden. Die statischen Festigkeiten liegen über denen konventionell geschweißter Nähte. Gegenüber dem ungeschweißten Zustand ist allerdings auch bei diesen Nähten ein erheblicher Einbruch der Ermüdungsfestigkeit festzustellen.
High‐speed, thermally modulated SFE/GC for the analysis of volatile organic compounds in solid matrices
Authors: Liu Zaiyou , Farnsworth Paul B. , Lee Milton L.
Published: May 2005

A coupled supercritical fluid extraction (SFE) and high‐speed gas chromatography (GC) system was developed which permits simultaneous sample extraction and analysis. A thermal desorption modulator at the head of a 50‐μm i.d. capillary column was used as an interface between the SFE and GC. The extraction fluid was first split between the modulator and a waste collection vessel. The substances introduced into the modulator were concentrated in the stationary phase and then released as a sharp injection pulse to the analytical column by electrical resistance heated thermal desorption. The modulator was operated at 10‐s time intervals, which generated consecutive concentration pulses to the column. These concentration pulses were separated into individual chromatograms by high‐speed GC. A set of chromatograms could be generated while the extraction proceeded. With this system, the extractant was sampled continuously so that the SFE process could be monitored in real time for selected components. Quantitative results could be extrapolated before extraction was complete from curves obtained by signal averaging of segmented chromatograms from the set.
High efficiency cross‐linked polyacrylamide coating for capillary electrophoresis of proteins
Authors: Huang Mingxian , Vorkink William P. , Lee Milton L.
Published: May 2005

A highly efficient cross‐linked polyacrylamide capillary coating has been developed for capillary electrophoresis of proteins. The fused silica capillary tubing was pretreated with 7‐oct‐1‐enyltrimethoxysilane and then statically coated with the polymerization reagents. The copolymerization reaction was performed at 120°C when using a free‐radical initiator. Coated columns were evaluated for the separation of both basic and acidic proteins. Methylene bisacrylamide was added in the preparation of the cross‐linked polyacrylamide coating, and the cross‐linking effects on column performance were evaluated. Both linear and cross‐linked columns gave high separation efficiencies and good reproducibilities for proteins, and electroosmotic flow was eliminated. It was found that the cross‐linked polyacrylamide coatings produced nearly double the efficiencies and only one third the relative standard deviations in migration times for proteins when compared to linear polyacrylamide coatings. Highly efficient and reproducible separations of proteins in human serum samples were achieved using the cross‐linked column.
2‐Dimethoxyphosphoryl‐1,3‐dithiane: A comparison of NMR studies for 1H, 13C and 31P nuclei by one‐ and two‐dimensional NMR techniques
Authors: Engelhardt Michael , Hägele Gerhard , Mikolajczyk Marian , Balczewski Piotr , Wendisch Detlef
Published: May 2005

2‐Dimethoxyphosphoryl‐1,3‐dithiane was obtained by the reaction of 2‐chloro‐1,3‐dithiane with trimethyl phosphite. Studies at 200, 360 and 400 MHz using 1H, 13C and 31P nuclei and 1D‐ and 2D NMR techniques are described. Long‐range coupling constants were extracted by iterative treatment of [AB]2CDMR6X spin systems. A rigid dithiane structure with axial phosphorus is consistent with the NMR results. Analogous dithianes and solid‐state structures are discussed.
Effect of lithium cation on the relaxation mechanisms of acids and alcohols
Authors: Lambert Joseph B. , Simpson Sharon Vlasak
Published: May 2005

The effect of lithium chloride on the relaxation mechanisms of simple acid and alcohols has been examined. Dipolar relaxation is predominant for acetic acid and ethanol. Lithium chloride (approximately 10%) significantly increases the rate of dipolar relaxation for all carbons and protons of acetic acid, probably through an increase in aggregate size or viscosity. Lithium chloride (approximately 1.5%) has a similar but smaller effect on the protons of ethanol. The methyl carbons and fluorines of trifluoroacetic acid and 2,2,2‐trifluoroethanol relax primarily by spin‐rotation. With about 10% lithium chloride, dipolar relaxation becomes more important for trifluoroacetic acid. With about 1.5% lithium chloride, trifluoroethanol possibly shows an enhancement of spin‐rotation relaxation for the CF3 nuclei.
Determination of the Karplus relationships for the C‐2, H‐1′ and C‐6, H‐1′ vicinal coupling paths of uridine derivatives
Authors: Davies David B. , Rajani Pramila , MacCoss Malcolm , Danyluk Steven S.
Published: May 2005

A number of uracil cyclo‐nucleosides with known glycosidic bond conformations have been synthesized as model compounds for evaluating the Karplus parameters of vicinal carbon‐proton coupling across the glycosidic bond. The magnitudes of 3J(C‐2, H‐1′) and 3J(C‐6, H‐1′) were determined from proton‐coupled 13C NMR measurements, and both coupling constants showed an approximate Karplus dependence with dihedral angle. Careful analysis of the results on model compounds reveals that the C‐2, H‐1′ and C‐6, H‐1′ coupling paths are not equivalent, and so the magnitudes of Karplus parameters have been determined for each coupling path for the Karplus relationship in the form 3J=A cos2 θ + B cos θ + C, i.e. A6 = 6.2, B6 = −2.4 and C6 = 0.1 Hz and A2 = 5.0, B2 = 2.1 and C2 = 0.1 Hz. Comparison is made between proton‐carbon coupling magnitudes in nucleoside and peptide coupling paths.
The structural dependence of geminal and vicinal CC coupling constants
Authors: Cho Jung‐hyuck , Klessinger Martin , Tecklenborg Ute , Wilhelm Konrad
Published: May 2005

CC coupling constants of ten bicyclic hydrocarbons and ten cyclic ethers or carbonyl compounds were determined from the satellites of broad band decoupled spectra or from INADEQUATE measurements. The influences of valence angles, dihedral angles, hybridization and heterosubstitution on geminal and vicinal CC coupling constants are discussed in terms of the algebraic additivity of the contributions from individual coupling paths within the framework of a multiple path mechanism.
119Sn and 1H NMR of the novel complexes [IrH(SnCl3)5]3‐ and [RhH(SnCl3)5]3‐
Authors: Yamakawa Tetsu , Shinoda Sumio , Saito Yasukazu , Moriyama Hiroshi , Pregosin Paul S.
Published: May 2005

New anionic complexes, [IrH(SnCl3)5]3‐ and [RhH(SnCl3)5]3‐, in which the hydride ligands are stabilized only by SnCl3− ligands, have been characterized by 119Sn and 1H NMR spectroscopy. These pentakis SnCl3− complexes are contained in catalyst solutions for the liquid‐phase dehydrogenation of propan‐2‐ol yielding acetone and dihydrogen.
NMR characterization of functional groups: 9‐isomer ratios of available chloromethylstyrene mixtures
Authors: Manatt Stanley L. , Khune G. D. , Khatri N. A.
Published: May 2005

From the assignments of the 1H and 13C 11.7 tesla NMR spectra of available mixtures of m‐ and p‐chloromethylstyrene, the proportion of the meta and para compounds are easily determined. For these materials from two common commercial sources, proportions of 72 and 28% and 68 and 32% were found. These concentrations are substantially different from the often assumed 60 and 40% for the meta and para compounds, respectively. The influence of this difference on the desired properties of copolymers made from such mixtures is discussed. An alternative quantitative procedure for determining the chloromethyl group isomer ratios is also described which employs silver trifluoroacetate in acetone displacement of chloride and 19F NMR examination of the resulting ester mixture with a 2.3 tesla spectrometer.
Nuclear magnetic resonance III‐13C NMR spectral studies on substituted indoles
Authors: Biswas K. M. , Dhara R. N. , Mallik H. , Roy S.
Published: May 2005

13C signal assignments of 3‐ethyl‐1‐methylindole (1), 1‐methyl‐3‐phenylindole (3), 1,3‐dimethyl‐2‐phenylindole (5), 1‐methyl‐2,3‐diphenylindole (10), 1,5‐dimethyl‐2,3‐diphenylindole (12), 7‐methoxy‐2,3‐diphenylindole (13), 7‐methoxy‐4‐methyl‐2,3‐diphenylindole (14) and 1‐(7‐methoxy‐4‐methyl‐2,3‐diphenyl‐6‐indolyl)‐1‐(7‐methoxy‐2,3‐diphenyl‐4‐indolyl)methane (15) are reported. Contrary to an earlier report on monophenylindoles, the para carbons of the phenyl groups of 3, 5, 10 and 12–15 resonate at lower frequencies than their ortho carbons. The methoxy carbon at position 7 in 15 absorbs at a higher frequency than other similar carbons in 13–15 owing to steric inhibition to resonance.
Motional anisotropy‐induced unequal deuterium NMR spin‐lattice relaxation of 3α‐deuteriocholesterol and 3β‐deuterioepi‐cholesterol in solution as a measure of sterol motion about the molecular axis
Authors: Murari Martha P. , Murari Ramaswamy , Baumann Wolfgang J.
Published: May 2005

Deuterium spin‐lattice relaxation (T1) data for 3α‐deuteriocholesterol and 3β‐deuterioepicholesterol in solution were obtained at 12.21 MHz as a function of solvent viscosity (η). The correlation times (τc) for both 3‐deuteriosterols varied in a linear fashion over the range of viscosities studied. The data showed that although both 3α‐deuteriocholesterol and 3β‐deuterioepicholesterol undergo rapid reorientations (τc ≈︁ 10−11s) in solution, the relaxation of the deuterium in 3β‐deuterioeholesterol was approximately 2.5 times faster than in 3β‐deuterioepicholesterol. These unequal rates of relaxation are due to the difference in the angles between the CD bond and the molecular axis for the two sterol isomers. An equation containing an angular‐dependent term was derived to analyze the T1 data further. The effective correlation times (τeff), thus calculated, converged for identical viscosities. In the case of 3α‐deuteriocholesterol, it was determined that rotation about the molecular axis comprised up to 60% of the motions relaxing the deuteron. The results show that for molecules having an inherent anisotropy and undergoing isotropic motions, it is possible to separate the portion of motion due to rotation about the molecular axis from other motions which contribute to the relaxation processes at a specific center.
Carbon‐13 NMR Spin‐Lattice Relaxation and Molecular Motion in 2‐Phenyl‐1,3,2‐dioxarsolane and its 4‐Methyl and 4,5‐Dimethyl Derivatives
Authors: Aksnes D. W. , Ramstad K.
Published: May 2005

13C NMR spin‐lattice relaxation times (T1) have been measured as a function of temperature for three 2‐phenyl‐1,3,2‐dioxarsolanes. The T1 data have been interpreted in terms of isotropic overall molecular reorientation, internal rotation about the AsPh bond and internal methyl rotation. Information on the relative order of magnitude of the overall and internal reorientations has been obtained. The internal rotation of the phenyl ring is thus 2—4 times faster than the overall molecular tumbling. Further, the internal rotation of the arsolane ring appears to be comparable to, or slightly faster than, the phenyl ring rotation. The association process which is believed to take place in the unsubstituted parent compound is reflected in its very high activation energy for overall reorientation (39 kJ mol−1 compared with 24‐25 kJ mol−1 for the methyl derivatives). The rotation of the methyl groups appears to be considerably more hindered in the cis isomer of 2‐phenyl‐4,5‐dimethyl‐1,3,2‐dioxarsolane than in the trans isomer and, in particular, the mono‐4‐methyl compound.
Carbon‐13 delta shifts and steric interactions in N‐aryl‐1‐isoindolinones and Isoindoline‐1,3‐diones
Authors: Khadim Mohammad A. , Colebrook L. D.
Published: May 2005

Consistently deshielding 13C δ shifts resulting from the presence of aryl ortho substituents have been measured for the 3‐methylene carbon atoms of some N‐aryl‐1‐isoindolinones (0.12‐3.25 ppm) and for the carbonyl carbon atoms of these compounds and corresponding N‐arylisoindoline‐1,3‐diones (0.04‐1.47 ppm). Low‐temperature (−75 and −150 °C) 1H NMR studies indicate that steric barriers to internal rotation about the aryl CN bonds in the N‐aryl‐1‐isoindolinones are low. The compounds with the bulkiest aryl ortho substituents tend to show the largest δ shifts (particularly for the 3‐methylene carbons). No consistent correlation with the size of aryl ortho‐substituents or their expected electronic properties is evident.
Two‐dimensional INADEQUATE 13C NMR Study on Vitamin D3
Authors: Kruk C. , Jans A. W. H. , Lugtenburg J.
Published: May 2005

Two‐dimensional INADEQUATE 13C NMR spectroscopy has been used to find the carbon‐carbon connectivities of the carbon skeleton of vitamin D3. This information leads to the unambiguous assignment of the chemical shifts of all 27 carbon atoms of vitamin D3.
17O NMR spectroscopy of 4‐substituted pyridine N‐oxides: Substituent and solvent effects
Authors: Boykin D. W. , Baumstark A. L. , Balakrishnan P.
Published: May 2005

The 17O chemical shifts for 4‐substituted pyridine N‐oxides at natural abundance were measured in acetonitrile at 50°C. Electron withdrawing groups caused deshielding and electron donating groups caused shielding of the 17O resonance. The data are correlated with 17O chemical shifts of substituted anisoles by DSP treatment and with ionization potentials. The chemical shift range for the substituents (methoxy to nitro) is exceptionally large (102 ppm). The 17O signal of the pyridine N‐oxides is substantially shifted in aqueous solution; the differences in chemical shifts between acetonitrile and water for the nitro, parent and methoxy compounds are 85, 75 and 59 ppm, respectively.
Heavy metal spin‐ ½ nuclei. Platinum‐195 relaxation times in phosphorus‐platinum(o) compounds and their dependence on the geometry of the complex
Authors: Benn Reinhard , Michael Büch Holger , Reinhardt Rolf‐Dieter
Published: May 2005

The 195Pt NMR parameters of several phosphorus‐platinum(O) complexes [LnPt(O), L = phosphine or phospite, n = 2, 3, 4] have been investigated to illustrate the particular NMR properties of a spin‐1/2 heavy metal nucleus, and for elucidation of their dependence on the geometry of the complexes. In these compounds the T1 values vary as a function of the coordination number, n, over several orders of magnitude and, therefore, can be used as structure‐dependent parameters. In L2Pt complexes the relaxation rate varies with Bo2, and chemical shift anisotropy (CSA) is the dominant relaxation mechanism. In the L3Pt and L4Pt complexes spin‐rotation increasingly contributes to the relaxation. For the tirethylphosphine‐platinum complex (L3) the contribution of CSA is reduced by 45% at 7 T and 240 K, whereas the tetrahedral trimethylphosphine‐platinum (L4) and triethyl phosphite‐platinum (L4) complexes relax mainly by spin‐rotation even at 9.4 T.
Steric interaction between the peripheral substituents of 10(S)‐chlorophyll derivatives and its conformational consequences: A proton magnetic resonance study
Authors: Hynninen Paavo H. , Lötjönen Simo
Published: May 2005

The improved methods developed recently for the preparation of 10(S)‐chlorophyll derivatives have permitted a detailed comparison of their conformations with those of the corresponding 10(R) derivatives, utilizing 1H NMR spectroscopy. Starting from the highly purified 10(S) derivative and following its conversion to the corresponding 10(R) form by repeated 1H NMR spectral measurements in acetone‐d6, reliable values for the differences in the chemical shifts (Δδ) for each epimeric pair of compounds have been obtained. The relatively large Δδ values (0.1–0.2 ppm) observed for the P‐1‐CH2, P‐H‐2, P‐3a‐CH3 and 10b‐CH3 signals were interpreted as indicating the proximity of the C‐10 methoxycarbonyl group and the olefinic region of the phytyl group in the 10(S) derivatives. The proximity between these side‐chains was considered to be derived principally from the three closely spaced carbonyls in the 10(S) derivatives. To minimize repulsion among the carbonyls, the C‐7 and C‐10 side‐chains presumably assume conformations allowing maximal mutual distances for the carbonyls. As a compromise of various energetic factors, the phytyl group takes up a conformation where it bends to the right hand side of the macrocycle, or above rings V and III. This results in steric crowding between the olefinic region of the phytyl group and the C‐10 methoxycarbonyl group. In addition, the other chemical shift increments show that the steric crowding between the bulky side‐chains of the 10(S) derivatives increases the steric strain at the periphery of the macrocycle, relieved by pronounced conformational changes in rings IV and V and, to a lesser extent, also in the whole phorbin ring. The conformational differences were found to be larger for the magnesium‐free epimers than for the chlorophylls. In the former case, they were also manifested by relatively large Δδ values (0.1–0.5 ppm) for the pyrrole NH protons.
Concerted use of two‐dimensional NMR techniques in the ab initio assignment of complex spectra: Complete proton and carbon‐13 assignment of oligomycin A
Authors: Morris Gareth A. , Richards Michelle S.
Published: May 2005

The identification and complete 13C and 1H assignment of a sample of oligomycin A is described. 13C multiplicities were determined by the INEPT method; assignments were made by comparison of heteronuclear 13C‐1H chemical shift correlation, homonuclear COSY and homonuclear relayed coherence transfer two‐dimensional NMR spectra.
17O NMR spectroscopy of heterocycles. Steric effects for N‐oxides
Authors: Boykin D. W. , Balakrishnan P. , Baumstark A. L.
Published: May 2005

The 17O chemical shift data for a series of 2‐ and 4‐alkyi‐ and ‐aryl‐substituted pyridine N‐oxides, as well as those for quinoline N‐oxide (13), benzo[f]quinoline N‐oxide (14) and benzo [h]quinoline N‐oxide (15) at natural abundance were measured in acctonitrile at 75°C. 2‐Alkyl groups cause a deshielding effect on the N‐oxide chemical shifts compared with those of the 4‐alkyl isomers. The largest effects are noted for 2‐tert‐butylpyridine N‐oxide (8) and 2,6‐dimethylpyridine N‐oxide (12). Similarly, the 17 O chemical shift of 15 is deshielded by 18 ppm compared with that of 13 and 14. 17O chemical shift data were obtained for 2‐and 4‐tert‐butylanisoles and compared with those of 8 and 4‐tert‐butylpyridine N‐oxide (9). The sensitivity of the N‐oxide 17O chemical shifts was substantially greater than that for the anisoles, an effect that was also observed in an analysis of the 13CNMR data of the tert‐butyl groups of 8 and 9. Steric inhibition of resonance is noted for 3‐methyl‐4‐nitropyridine N‐oxide; the N‐oxide 17O signal was shielded and the NO2 17O signal was deshielded relative to those for 4‐nitropyridine N‐oxide.
Carbon‐13 and proton NMR spectra of 1(2H)‐isoquinolinone, 1(2H)‐phthalazinone, 4(3H)‐quinazolinone and their substituted derivatives
Authors: Spassov S. L. , Atanassova I. A. , Haimova M. A.
Published: May 2005

The 13C NMR chemical shifts, one‐bond and some long‐range 13C–1H coupling constants and the 1H NMR chemical shifts for isoquinolinone, phthalazinone, quinazolinone and their derivatives containing CH3, COOH, COOCH3 and CH2COOH substituents in the hetero‐ring are reported. The NMR data are in agreement with the lactam structure for all compounds studied; no evidence for the detectable presence of other tautomers was obtained.
14N nuclear quadrupole resonance in substituted isatin compounds
Authors: Bray P. J. , Mulkern R. V. , Greenbaum S. G.
Published: May 2005

14N nuclear quadrupole resonances have been found for eight substituted isatin compounds. Variations in the electric field gradient (EFG) and asymmetry parameter, η, have been attributed to inductive rearrangement of the electron distribution at the nitrogen site. A correlation between the inductive Taft parameter, σ*, of the substituent and the charge density difference between the hybridized nitrogen bonding orbitals, σNHσNc, has been established. Implications of the results with respect to the available biological data on substituted isatins are discussed.
13C NMR and azomethine 1H NMR spectra of substituted N‐benzylideneanilines and hammett correlations
Authors: Echevarria Aurea , Miller Joseph , Nascimento M. Graça
Published: May 2005

Twenty‐four N‐benzyliaeneanilines (four being new compounds) have been prepared, which are divided conveniently into three series: (I) with 4‐substituents, plus one compound with 3‐ and 4‐substituents; (II) with 4′‐substituents, plus one compound with 3′‐ and 4′‐substituents; and (III) with 4‐ and 4′‐substituents. Their 13C NMR spectra and the 1H NMR absorption of the hydrogen attached to the imidoyl carbon atom have been studied and their Hammett correlations were tested.
ESR of cation radicals of phenothiazine derivatives
Authors: Motten Ann G. , Chignell Colin F.
Published: May 2005

Phenothiazines are of interest as model heterocyclic compounds and also as pharmacological agents with a wide spectrum of biological activities. Cation radicals derived from six phenothiazine derivatives including phenothiazine, 2‐chlorophenothiazine, promazine, chlorpromazine, promethazine and trimeprazine have been studied in aqueous solution by electron spin resonance. Their high‐resolution electron spin resonance spectra have been fully analysed, and hyperfine splitting parameters have been compared with those obtained in other solvent systems where available. Previously undetected hyperfine splittings of about 0.2–0.4 G from γ‐protons on the alkyl chain were observed for promazine, promethazine and, possibly, chlorpromazine.
A 15N NMR study of some fused polyaza heterocyclic ring systems
Authors: Kaczmarek L. , Nantka‐Namirski P. , Stefaniak L. , Webb G. A. , Davoust D. , Basselier J. J.
Published: May 2005

15N NMR spectroscopy was used to distinguish between isomers and to characterize some series of novel fused polyaza heterocyclic ring systems. Support for the assignments was provided by means of some INDO/S‐SOS shielding calculations. Previously observed shielding trends, as a function of nitrogen type, are reproduced in the present set of molecules.
13C NMR spectroscopy of functionalized alkenyl and cycloalkenyl cyclopropanes
Authors: Chalchat J. C. , Garry R. Ph. , Lacroix B. , Michet A.
Published: May 2005

The 13C NMR spectra of ninety‐eight functionalised alkenyl and cycloalkenylcyclopropanes are described. The chemical shifts of specific carbon atoms, and the evaluation of certain pairwise contribution parameters between the substituents, provide information on the structure of the considered compounds.
13C NMR data bank techniques as analytical tools
Authors: v. d. Lieth C. W. , Seil J. , Köhler I. , Opferkuch H. J.
Published: May 2005

Various applications of computer programs which allow the automatic use of spectral and structural information from the SPEKTREN 13C NMR data bank are presented. A method of classifying clusters in a distribution of shifts belonging to the same substructure code is described and the reliability of the prediction of spectra is discussed. The influence of the size of the ‘shift window’ for spectral match was tested. The usefulness of the combination of spectroscopic and substructural information in various ways is illustrated, and the integrity of the used data base is tested with different methods.
NMR study of molecules in anisotropic systems. III—Structure and orientation of 1a,2a,3e,4e,5e,6a‐hexachlorocyclohexane in a nematic liquid crystal determined from low‐temperature experiments
Authors: Fujiwara Hideaki , Shimizu Naoto , Takagi Tatsuya , Sasaki Yoshio
Published: May 2005

1H NMR spectra of 1a,2a,3e,4e,5e,6a‐hexachlorocyclohexane (γ‐BHC) have been measured in a nematic solution of ZLI2081 at low temperatures to prevent exchange broadening. The spectra were analysed and direct couplings determined. The six‐membered ring is most favourably oriented parallel to the solvent molecule. The principal axes of the order matrix differ from those of the moment of inertia, and the difference is explained as being due to the steric effect of the three axial chlorine atoms. The molecular structure of γ‐BHC in nematic solution is found to differ from that calculated from the MNDO MO method, but resembles that in the crystal determined by x‐ray spectrometry.
Application of two‐dimensional NMR spectroscopy to the analysis of the proton NMR spectrum of sparteine and its lactams
Authors: Gołȩlebiewski W. Marek
Published: May 2005

Combined application of two‐dimensional 1H–1H homonuclear chemical shift correlation, two‐dimensional J‐resolved 1H NMR measurements and double resonance experiments permitted the specific assignment of the signals in the 1H NMR spectra and of the 1H–1H coupling constants of sparteine and its 2‐, 15‐ and 17‐oxo and 2,17‐dioxo derivatives. The results provide information on the conformation of these alkaloids.
Conformational studies on some phthalideisoquinoline derivatives
Authors: Kövér Katalin E. , Kerekes P.
Published: May 2005

The molecular conformation of phthalideisoquinoline derivatives was studied by 1H NMR methods. For the qualitative determination of the conformational preferences, proton relaxation times, 1D and 2D NOE experiments were applied. Our proposals were supported by the calculation of the effects of ring currents.
Conformational analysis. XXVII—A 1H and 13C NMR conformational study of cis‐ and trans‐annelated 2‐p‐nitrophenyl‐4,5‐ and ‐5,6‐tetramethyleneper‐hydro‐ and 2‐p‐chlorophenyl‐4,5‐ and ‐5,6‐tetramethylenedihydro‐1,3‐oxazines
Authors: Pihlaja Kalevi , Mattinen Jorma , Bernáth Gábor , Fülöp Ferenc
Published: May 2005

The 400 MHz 1H NMR spectra of cis‐ and trans‐annelated 2‐p‐nitrophenyl‐4,5‐ and ‐5,6‐tetramethyleneperhydro‐ and 2‐p‐chlorophenyl‐4,5‐ and ‐5,6‐tetramethylenedihydro‐1,3‐oxazines were recorded. The AMKX subspectra due to the protons at C‐4, C‐5 and C‐6 were analysed. Both cis‐ and trans‐annelated an equatorial 2‐p‐nitrophenyl group, as concluded from the values of their vicinal coupling constants and those in some simple model compounds, in agreement with the information given by 13C NMR and low‐temperature experiements. Correspondingly, trans‐2‐p‐chlorophenyl‐4,5‐ and ‐5,6‐tetramethylenedihydro‐1,3‐oxazines exist in anancomeric conformations; the cis isomers, however, are equilibrium mixtures of the N‐ or O‐eq and N‐ or O‐ax forms where the latter predominate, as shown by vicinal H, H coupling constants, 13C chemical shifts and low‐temperature experiments.
Synthesis and NMR analysis of isotopically enriched methanol
Authors: Walker T. E. , Wageman W. E.
Published: May 2005

Four isotopomers of methanol were prepared enriched with 13C, 12C, and deuterium, including [13C, 2H4]methanol, [13C]methanol, [12C, 2H4]methanol and [12C]methanol. These compounds were analysed by proton NMR and by deuterium and 13C NMR, both proton coupled and decoupled. The spectra are useful for calculating the isotopomer distribution and for determining the percentage enrichment in the labeled positions, for which each spectrum provides unique information. A variety of coupling constants and isotope shifts are also reported.
1H NMR investigation of 10‐dimethylaminononafulvene
Authors: Otter Albin , Neuenschwander Markus , Kellerhals Hans Peter
Published: May 2005

The 1H NMR spectrum of 10‐dimethylaminononafulvene (2) has been analysed under high‐resolution conditions at low temperature. Chemical shifts and 27 non‐zero J values are reported. None of the parameters are significantly influenced by changes in solvent or temperature. The results indicate that 2 is not planar, and contains two sterically very different ring segments: a nearly planar (E)‐configurated dienamine system consisting of atoms N—(C‐10)—(C‐9)—(C‐8)—(C‐7) is linked to a triene system deviating strongly from planarity.
13C and 31P NMR spectra of 1‐diethylphosphono‐1‐hydroxycycloalkanes
Authors: Buchanan G. W. , Bourque K. , Seeley A.
Published: May 2005

13C and 31P NMR chemical shifts and 13C‐31P couplings are reported for a series of thirteen 1‐diethylphosphono‐1‐hydroxycycloalkanes and their alkyl derivatives with carbocyclic ring sizes varying from four to twelve.
1J(CC) and 3J(CC) coupling constants in monosubstituted anilines. Additivity of substituent effects on carbon–carbon couplings
Authors: Sándor Péter , Radics Lajos
Published: May 2005

Isotropic carbon–carbon coupling constants over one and three chemical bonds have been measured in ortho‐, meta‐ and para‐substituted anilines, C6H4NH2X (X = F, Cl, Br, I, OCH3, NH2, NO2, CN, COOCH3, CH3), in natural abundance. The experimental data are compared with J(CC) values calculated by assuming additivity of substituent coupling increments. Additivity conditions are discussed. Non‐additivities are interpreted, on a qualitative level, in terms of mesomeric and inductive interactions between the substituents.