bluuebunny/crossref_metadata_2025 huggingface dataset:
Verschleiß – eine Systemeigenschaft Auswirkungen auf die Verschleißprüfung
Authors: Heinke G.
Published: May 2005

Verschleißforschung, Verschleißprüfung und Verschleißabwehr müssen davon ausgehen, daß Verschleiß die Eigenschaft eines Systems ist, bestehend aus Konstruktionsgrößen und Beanspruchungsgrößen.

Verschleißkenngrößen sind deshalb nur aus Systembetrachtungen ableitbar, und die Verschleißprüfung muß sich am speziellen praktischen Verschleißsystem orientieren.

Verschleißsysteme werden mit Hilfe von Modell‐, Bauteil‐, Erzeugnis‐ und Praxisversuchen untersucht und geprüft. Trotz Mängel hat die Modell‐ und Bauteilprüfung unter bestimmten Bedingungen ihre Berechtigung bei der Entwicklung praktischer Verschleißsysteme.

Als Beispiel wird ein Bauteil‐ und Modellprüfstand zur Simulation von Gleitverschleißvorgängen unter Misch‐ und Grenzreibungsbedingungen beschrieben. Neben statischen Beanspruchungen sind auch dynamische Verschleißbeanspruchungen simulierbar.
Mikrobereichs‐ und Oberflächenanalyse in der Werkstoff‐Forschung
Authors: Dudek H. J.
Published: May 2005

Die Eignung und die Grenzen der Verfahren der Mikrobereichs‐ und Oberflächenanalyse für die Untersuchung von Werkstoffproblemen werden unter Anwendung von, der analytischen Chemie analogen, Kriterien diskutiert. In die Betrachtungen einbezogen werden die Elektronenstrahl‐Mikroanalyse (ESMA), die Auger Elektronen Spektroskopie (AES), die Röntgenphotoelektronen Spektroskopie (XPS) sowie die Röntgen‐Mikroanalyse (EDX) und die Elektronen‐Energieverlust Spektroskopie (EELS) in der analytischen Transmissions‐Elektronen‐Mikroskopie (ATEM). Als Kriterien für die Einsetzbarkeit dieser Verfahren in der Werkstoff‐Forschung werden die allgemeine Anwendbarkeit, die Nachweisgrenze, die Reproduzierbarkeit, die quantitative Analyse, die Ortsauflösung und die bindungsspezifischen Informationen betrachtet.
Wasserstoffversprödungsanfälligkeit hochfester Werkstoffzustände Teil 1: Wasserstoffversprödungsanfälligkeit aus metallkundlicher Sicht
Authors: Kloos K. H. , Beyer St.
Published: May 2005

Nach den Ausführungen in 2.1 und 2.2 können hoch‐ und höchstfeste Vergütungszustände sowie einsatzgehärtete und einsatzvergütete Werkstoffzustande hinsichtlich ihrer Wasserstoffversprödungsanfälligkeit nach rein metallkundlicher Sicht ähnlich beurteilt werden:

Wasserstoffinduzierte interkristalline Brüche scheinen nur in Anwesenheit von Korngrenzenverunreinigungen aufzutreten.

Die Wasserstoffversprödungsanfälligkeit ist am höchsten im Bereich der dritten Anlaßstufe, wo zunehmende ε‐Karbidauflösung auf den Subkorngrenzen und anwachsende Karbidfilmbelegung auf den Lattengrenzen des Massivmartensits und den ehemaligen Austenitkorngrenzen stattfindet. Für übliche Einsatzstähle ist dies im allgemeinen der Anlaßtemperaturbereich zwischen 200–400 °C. In diesem Bereich durfte das Gefüge gemäß 2.1 zum überwiegenden Teil reversible Fallen enthalten. Die reversiblen Fallen werden einerseits durch die gelösten Korngrenzenverunreinigungen (P, N, S, usw.) repra. für Wasserstoff bildet. Das bedeutet, daß Wasserstoffanreicherungsmechanismen hier besonders wirksam werden können und insbesondere unter Zugbeanspruchung ortlich kritische Wasserstoffkonzentrationen schneller erreicht werden.

Legierungselemente können sowohl den Versprödungsgrad einer Anlaßversprödung als auch den Temperaturbereich der Versprödungsanfälligkeit maßgeblich beeinflussen. Da eine deutliche Korrelation zwischen dem Temperaturbereich einer Anlaßversprödung – auch wenn diese nur latent vorhanden ist – und der Wasser‐ stoffversprödungsanfälligkeit besteht, ist es insbesondere bei Vergütungsstahlen mit Elementen wie Mo oder Ni, die Vorgänge der dritten Anlaßstufe zu höheren Anlaßtemperaturen verschieben können, moglich, daß auch die Wasserstoffversprödungsanfälligkeit bis zu Anlaßtemperaturen von 450–500 °C bestehen bleibt.
Quecksilberporosimetriemessungen an durch Druckwasserstrahlen beanspruchten Betonproben
Authors: Momber A.
Published: May 2005

Der Beitrag beschreibt das Verhalten von Zementstein und Betonen bei der Beanspruchung durch Flüssigkeisstrahlen hoher Geschwindigkeit. Mittels Quecksilberporosimetriemessungen und Korngrößenanalysen wird festgestellt, daß der Versagensvorgang bruchmechanisch orientiert ist und daß das Verhalten deutlich durch die Zuschlagstoffkörner beeinflußt wird.
Long‐term Creep Behavior of austenitic steel S‐590 (X 40 CoCrNi 20 20)
Authors: Bürgel R.
Published: May 2005

Typical data from discontinuous long‐term stress rupture tests were adapted for a differentiated creep analysis. A test series of more than 2000 000 h (23 years) single test time was available for austenitic steel S‐590. This alloy was formerly used for high temperature applications. Various factors influence the creep behavior and cause anomalies from classical three‐stage creep division. These phenomena are: microstructural instability, early creep damage (cavitation, microcracks) and corrosion. Typical features of diffusion creep were not observed. The procedure used in this examination and the principal findings can be applied to other high temperature materials.
Bewertung von Oberflächenrissen mit Methoden des plastischen Versagens
Authors: Keller H. P.
Published: May 2005

Untersuchungen an Flachzugproben und Behältern aus Vergütungs‐ und Feinkornbaustählen mit etwa halbelliptischen Oberflächenrissen haben gezeigt. Daß die Versagensspannung nach Verfahren des plastischen Versagens konservativ ermittelt wird. Während sie nach dem Ansatz von Harrison und dem Fließkriterium von Mises – unabhängig von der Rißtiefe – im Mintel um etwa 10% unterschätzt wird, bewerten die anderen untersuchten Verfahren (Mattheck, Chell) deutlich konservativer. Der Grad der Unterschätzung wächst von etwa 30 bzw. 40% bei mittleren Rißtiefen bis zu 70% bei tiefen Rissen. Für einseitigen Wasserstoffangriff auf der Rißausgangsseite ergaben sich i.a. die gleichen konservativen Bewertungen wie bei Luftumgebung.

Die Untersuchung hat weiterhin gezeigt, Daß die Versagensspannung von Fluchzugproben unter Luft‐ und Wasserstoff‐Atmosphäre mit etwa konstanter Rißtiefe mit guter Genauigkeit berechnet werden kann, wenn im Restquerschnitt der Mittelwert zwischen Streckgrenze und Zugfestigkeit als Fließspannung angesetzt wird.

Es ist für ähnliche Bauteile zu erwarten, daß die erarbeiteten Ergebnisse auf Werkstoffe mit vergleichbaren Rißzähigkeits‐ und Festigkeitseigenschaften übertragbar sind.
Degradation and regeneration of the cross‐linking agent azo‐t‐butane
Authors: Shaw Timothy J. , Jones Brian A.
Published: May 2005

The ability of commercially available azo‐t‐butun (ATB) to facilitate immobilization of polysiloxane stationary phases in capillary columns deteriorates upon storage. Aged ATB produces columns with high bleed, solute retention shifts, erratic immobilization efficiency, and high activity. This deterioration is accelerated in the presence of light, suggesting free radical processes are involved. The loss of certain lowlevel impurities, which act as free radical transfer agents or radical sinks, may be responsible for the performance change. Regeneration can often temporarily be accomplished using platinum catalyzed reduction with trichlorosilane. The addition of small amounts of toluene or other radical transfer agents to aged ATB moderates the cross‐linking process, allowing the reproducible production of columns with good immobilization efficiency, excellent intertness, low thermal bleed, and proper polarity.
Parkinsonian features of eight pathologically diagnosed cases of diffuse lewy body disease
Authors: Louis Elan D. , Goldman James E. , Powers James M. , Fahn Stanley
Published: May 2005

Premortem diagnosis of diffuse Lewy body disease (DLBD) is difficult, and knowledge of the parkinsonian features of DLBD might facilitate the diagnosis. In this study, we compared the parkinsonian syndrome of DLBD and Parkinson's disease (PD). We retrospectively reviewed the charts of Columbia‐Presbyterian Medical Center (CPMC) Brain Bank cases (1989–1993) with pathologically diagnosed DLBD or PD, and the literature on the parkinsonian features in DLBD patients presenting with parkinsonism. Parkinsonism accompanied or preceded cognitive/psychiatric changes in most CPMC cases (DLBD 100%, PD 88%). DLBD had an earlier mean age of onset than PD did (57 versus 64 years), a similar male: female ratio (1.7:1 versus 1.9:1), and similar mean disease duration (12–13 years). Cognitive/psychiatric changes were less frequent in PD than in DLBD (65 versus 100%) (p = 0.025). Rest tremor was specifically mentioned in 29% of DLBD versus 56% of PD (p = 0.10). Bradykinesia was less common in PD (56% versus 86%) (p = 0.05). All those with PD responded to L‐Dopa, as did all those with DLBD who received L‐Dopa. In conclusion, there are subtle differences between PD and DLBD in age of onset, frequency of cognitive/psychiatric changes, bradykinesia, and rest tremor. However, even when taken together, these cannot be used to distinguish these entities.
Intramolecular motion and reorientational barriers in 9‐fluorenone, 4‐methyl‐9‐fluorenone and 4,5‐dimethyl‐9‐fluorenone
Authors: Wilson Nancy K.
Published: May 2005

Carbon‐13 nuclear magnetic resonance spin‐lattice relaxation times and nuclear Overhauser enhancements were measured as functions of temperature for the hydrogen‐bearing carbons in 9‐fluorenone, 4‐methyl‐9‐fluorenone and 4,5‐dimethyl‐9‐fluorenone. Reorientational diffusion constants were obtained from the dipolar T1 values. Isotropic overall molecular motion was assumed, and the methyl group rotation was separated from the overall molecular reorientation by the method of Woessner. Arrhenius plots of the dependence of the rotation rates on temperature provided values of the energy barriers for molecular reorientation and methyl group rotation. The energy barriers for molecular reorientation are essentially the same: 9‐fluorenone 11.8 ± 0.5 kJ mol−1, 4‐methyl‐9‐fluorenone 11.9 ± 0.5 kJ mol−1 and 4,5‐dimethyl‐9‐fluorenone 11.7 ± 0.2 kJ mol−1. The barriers to methyl group rotation are 4‐methyl‐9‐fluorenone 7.8 ± 0.9 kJ mol−1 and 4,5‐dimethyl‐9‐fluorenone 11.0 ± 0.5 kJ mol−1. Thus the bay methyl‐methyl steric interaction in 4,5‐dimethyl‐9‐fluorenone increases the methyl rotational barrier by 3.2 kJ mol−1.
A Study of steric and electronic effects in some methane‐ and dimethane‐sulphonanilides by 13C NMR spectroscopy
Authors: Hasan Misbah Ul , Asrof Ali Sk.
Published: May 2005

The steric and electronic interactions in several methanesulphonanilides and dimethane‐sulphonanilides have been examined on the basis of their 13C NMR chemical shifts. In aromatic amines there is evidence of nitrogen electron pair donation into the aromatic ring. However, the substitution of a methanesulphonyl group on nitrogen, as in N‐phenylmethanesulphonamide, causes a decrease in this resonance interaction. The chemical shifts of ortho‐ and para‐carbons therefore move downfield in comparison with the corresponding amines. Substitution of the aromatic ring at the para position by electron‐withdra wing and electron‐donating groups affects the resonance process. The substitution of methyl groups either at nitrogen or at the ortho positions causes severe steric inhibition of resonance, which is clearly reflected in the chemical shifts of these compounds. The chemical shifts in several dimiethane‐sulphonanilides have also been examined and compared with the shifts in the corresponding methanesulphonanilides. The observed differences are explained in terms of steric, mesomeric and inductive interactions in these molecules. The preferred conformations of these compounds in solution are also postulated on the basis of their chemical shifts.
Effect of nitrogen substituents on CN rotational barriers in enamine derivatives
Authors: Azzaro Marcel , Geribaldi Serge , Videau Bruno
Published: May 2005

Rates of rotation around the CN bond in a series of ten N,N‐disubstituted 3‐amino‐5,5‐dimethylcyclohex‐2‐enones were determined from total NMR line shape analysis. Linear correlations are shown to exist between Δ and parameters describing the inductive and steric effects of N‐alkyl substituents. The substituent effects on the barriers seem to occur mainly through a change in the potential energy of non‐bonded interactions between the nitrogen substituents and the hydrogen atoms in the ortho position to the amino group.
15N, 1H and 13C NMR. A study of the complexation of binuclear lanthanide(III)‐silver(I) shift or relaxation reagents with substrates containing multiply bonded nitrogen
Authors: Audit M. , Davoust D. , Goasdoue N. , Platzer N.
Published: May 2005

Binuclear lanthanide(III)‐silver(I) β‐diketonate chelates are effective NMR shift and relaxation reagents for substrates containing one or two multiply bonded nitrogen atoms, despite the fact that some of the substrates are able to react with lanthanide chelates alone. The silver cation is bonded to the nitrogen—nitrogen or nitrogen—carbon multiple bond. The lanthanide(III) chelate tetrakis anion is held in proximity to the substrate, without delocalization of spin density from the lanthanide to the studied nuclei (15N, 13C, 1H) of the substrate. Greater spectral simplification is achieved with a binuclear shift reagent than with a single lanthanide chelate in two ways. First, the complexation ability of the π electron pair may be greater than that of the heteroatom lone pair when that of the latter is lowered owing to steric (azobenzene, trans‐aldimine derivatives) or conjugative effects (benzonitrile is similar in this respect to heteroaryl substrates in which the heteroatom is devoid of basicity). Second, resolution may be far better preserved in cases where very strong binding to the lanthanide chelates results in extensive broadening of the NMR signals (imidazole, thiazole and oxazole derivatives).
Carbon‐13 NMR spectra of adamantane carboxylic acids and diamantane mono‐ and di‐carboxylic acids and esters
Authors: Hájek Milan , Vodička LuděK , Trška Petr , Sklenář Vladimír
Published: May 2005

The 13C NMR chemical shifts of 17 adamantane and diamantane mono‐ and di‐carboxylic acids and methyl esters have been measured in CDCl3, and D2O. The assignment of the chemical shifts was verified using an additivity rule and the lanthanide shift technique.
1H and 13C NMR spectra of the rotational isomers of N‐hydroxymethylamides and derivatives
Authors: Gate E. N. , Hooper D. L. , Stevens M. F. G. , Threadgill M. D. , Vaughan K.
Published: May 2005

A series of N‐hydroxymethylamides, RCONR′CH2OH, and their O‐methyl and O‐acetyl derivatives, have been studied by 13C and 1H magnetic resonance spectroscopy. Signals have been assigned to the E‐ and Z‐isomers on the basis of the analysis of the fully coupled spectra, and by comparison of the chemical shifts with those of model compounds. The introduction of the hydroxy, alkoxy or acetoxy groups at the α‐position of the N‐alkyl moiety causes a significant shift in the equilibrium towards the E‐rotamer compared with the unsubstituted N‐alkylamide. The predominant effect in determining the E: Z ratio appears to be the steric interaction between the carbonyl oxygen and the α‐oxygen in the alkyl moiety; intramolecular hydrogen bonding does not play a significant role in determining the rotamer populations of these molecules.
NMR of carboxylic‐17O in amino acids
Authors: Steinschneider A. , Valentine B. , Burgar M. I. , Fiat D.
Published: May 2005

17O NMR studies were conducted on the α‐COOH groups of the amino acids Val, Leu, Ile, His and Pro and on the γ‐COOH group of Glu. Limit chemical shifts, downfield from external water, were 249‐257 ppm in aqueous solution at low pH, and 234–243 ppm in HSO3F. The relative nuclear screening order for α‐COOH 17O between pH ‐1 and 13 and in HSO3F was usually Pro>Leu>His>Val>Ile, reflecting on interactions with the side chain. Concomitant with ionization in aqueous solution, the α‐ and γ‐COOH resonances were displaced to lower field, by 13–18 aid 24 ppm, respectively, presumably owing to overriding effects of the bond order‐charge density term in the paramagnetic contribution toward nuclear shielding. Titration with alkali above neutrality resulted in 2–4 ppm upfield shifts related to deprotonation of the α‐NH3+ group. T2 relaxation times were inversely related to the molecular weight. Line widths of amino acid 17O‐COOH resonances near neutrality were between 280 and 525 Hz, corresponding to T2 relaxation times between 0.6 and 1.1 ms. Titration from acidic to neutral pH increased T2 by up to 1.7‐fold. T1 measured for 17O‐Gly and γ‐17O‐Glu changed in parallel with T2. This was attributed to decreasing rotational correlation times, τc, in line with expected changes in the nuclear quadrupole coupling constant. τc values calculated from 17O relaxation in solutions near neutrality (zwitterion predominant) were in good agreement with τη, expected from solution properties and with the assumption of isotropic rotation. T2 decreased when the pH was increased above neutrality, partly owing to increasing solution viscosity.
NMR studies in the heterocyclic series xxv—13C NMR spectra of some azole dicyanomethylides
Authors: Begtrup Mikael , Elguero José , Díez‐Barra Enrique , Pardo Carmen
Published: May 2005

Chemical shifts and coupling constants are reported for seven azole derivatives (imidazoles, triazoles and their benzo derivatives), their quaternary salts and the corresponding dicyanomethylides. The assignment of the heterocyclic carbons is based on couplings with the N‐methyl group. Compared with neutral azoles the quaternary salts show irregular effects for the chemical shifts. On the other hand, the 13C chemical shifts of dicyanomethylides are similar to those of N‐methyl quaternary salts.
Carbon‐13 NMR spectra of anthraquinone‐derived dyes
Authors: Rubin I. B. , Buchanan M. V.
Published: May 2005

The 13C NMR spectra of six anthraquinone‐derived dyes, namely benzanthrone, 1‐(methylamino)anthraquinone, 1,4‐di‐p‐toluidinoanthraquinone, 1,4‐diamino‐2,3‐dihydroanthraquinone, 1,4‐diaminoanthraquinone and dibenzochrysenedione, have been measured. The chemical shift assignments were achieved by elucidation of the coupling patterns of the fully coupled spectra and by comparison with the chemical shifts of other anthraquinone derivatives and other model compounds. One‐ and three‐bond carbon‐hydrogen coupling constants are also reported.
15N NMR studies of the tautomeric equilibrium of some 1‐hydroxybenzotriazoles
Authors: Schilf W. , Stefaniak L. , Witanowski M. , Webb G. A.
Published: May 2005

By means of 15N NMR shielding measurements it is possible to obtain quantitative results on tautomeric equilibria for N‐hydroxybenzotriazole and its 4‐ and 6‐mononitro derivatives. For the unsubstituted compound the position of the tautomeric equilibrium is found to depend on the pKa value of the solvent. Intramolecular hydrogen bonding appears to be responsible for an increase in the proportion of the N‐oxide form present in the equilibrium mixture of the 4‐mononitro compound.
31P spin‐sattice relaxation times of tertiary aryl phosphines and their iridium(I) and gold(I) complexes
Authors: Jans‐Bürli S. , Pregosin P. S.
Published: May 2005

31P spin‐lattice relaxation times, T1, and 31P‐1H NOE values, η, for CDCl3, solutions of the compounds P(C6H4‐p‐X)3, [IrCl(CO){P(C6H4‐p‐X)3}2] (X = H, CH3, F, Cl, OCH3) and [AuCl{P(C6H4‐p‐X)3}] (X = H, OCH3) are reported. For the uncoordinated tertiary phosphines T1 = 26–28 s, except for X = OCH3 for which T1 = 14 s. For the iridium(I) complexes T1 falls in the range 4.4–8.7 s, whereas for the gold(I) compounds the values are 15.7 and 11.3 s for X = H and OCH3, respectively. The data are discussed in terms of the differing relaxation mechanisms within each class of compound. The unusually low T1 values observed when X = OCH3 is attributed to a relatively large change in the dipole‐dipole contribution to T1, such that T1 (dipole‐dipole) decreases.
Selective heteronuclear chemical shift correlation without soft pulses
Authors: Delsuc M. A. , Guittet E. , Lallemand J. Y.
Published: May 2005

The elucidation of 1H‐13C connectivities is one of the most powerful NMR tools for the determination of unknown structures, and a new one‐dimensional correlation technique is presented, based on a modified INEPT sequence. Omission of the first two 180° refocusing pulses and randomization of the mixing delay realize addition of a 13C bearing the selected 1H. This technique avoids resorting to the acquisition time and data storage consuming two‐dimensional approaches, and does not require any selective pulse or decoupling.
Non‐quaternary suppression with flip‐back: A useful technique for high‐resolution NMR of solids
Authors: Harris Robin K. , Kenwright Alan M. , Packer Kenneth J.
Published: May 2005

A modification to the well‐established non‐quaternary suppression pulse sequence used in high‐resolution solid‐state NMR is proposed which allows the inclusion of a ‘flip‐back’ pulse. The utility of such a sequence is demonstrated by spectra obtained using the standard and modified NQS sequences for a glycidyl ether derivative.
1H and 13C NMR spectra of (Z)‐N‐(o‐hydroxy‐benzylidene)‐p‐x‐phenylamine N‐oxides and (Z)‐N‐(2‐hydroxy‐1‐naphthylmethylene)‐p‐X‐phenylamine N‐oxides
Authors: Arumugam N. , Manisankar P. , Sivasubramanian S. , Wilson D. A.
Published: May 2005

Substituent effects on the 1H and 13C chemical shifts of (Z)‐N‐(o‐hydroxybenzylidene)‐p‐X‐phenylamine N‐oxides [(Z)‐α‐(o‐hydroxyphenyl)‐N‐p‐X‐phenyl nitrones] and (Z)‐N‐(2‐hydroxy‐1‐naphthylmethylene)‐p‐X‐phenylamine N‐oxides [(Z)‐α‐(2‐hydroxy‐1‐naphthyl)‐N‐p‐X‐phenyl nitrones] have been obtained. A combination of SFDOR and NOE methods was necessary for complete assignment of signals in the naphthalene series. Correlations have been found between the chemical shifts of various protons and carbons and Hammett o‐ parameters and Swain and Lupton F and R parameters. With both series of compounds a fixed conformation, due to intramolecular hydrogen bonding, is observed which affects the polarity of the nitrone group compared with that in α,N‐diphenyl nitrone. Reduced through‐resonance between aryl rings via the nitrone function was found. This may be attributed to the α‐aryl ring and the nitrone group being held out of coplanarity by the hydrogen bond.
Carbon‐13 chemical shift assignment of some organophosphorus compounds. Part 3. Diaryl‐, dialkoxy‐ and dihalo‐(alkylamido or arylamido) phosphorus derivatives with general formula Y2P(X)NHR
Authors: Al‐rawi Jasim M. A. , Ayed Naceur
Published: May 2005

Carbon‐13 chemical shifts and PC coupling constants of fifteen compounds containing the amine moiety and with the general formula Y2P(X)NHR are reported (Y=Cl, C2H5O, C6H5; Y2 = OCH2CH2O 1,2‐dioxybenzene: X = S, Se or O: R = Et, n‐Pr, n‐Bu, i‐Pr, t‐Bu, Ph, C6H11). The effects of sulphurization and selenization on J(PC) and on chemical shifts were verified.
Nitrogen and oxygen nuclear quadrupole and nuclear magnetic resonance spectroscopic study of NO bonding in pyridine 1‐oxides
Authors: Woyciesjes Peter M. , Janes Nathan , Ganapathy S. , Hiyama Yukio , Brown Theodore L. , Oldfield Eric
Published: May 2005

14N nuclear quadrupole resonance (NQR) spectra of the NO functional group in a series of 4‐substituted pyridine 1‐oxides (R = H, CH3, C6H5, OCH3, OCH2C6H5, Cl, CN, NO2) and the natural abundance 17O NQR and nuclear magnetic resonance (NMR) solution spectra of a number of selected systems were obtained. The orientations of the principal axes of the 14N electric field gradient tensor (efg) in the NO group were determined using a Townes‐Dailey treatment of the NQR results, combined with a 13C cross‐polarization magic‐angle sample‐spinning NMR line shape analysis of carbons bonded directly to nitrogen. The major principal axis (Z) is coincident with the NO bond. The orientation of the principal (Z) axis of the 17O efg tensor also lies along the N‐O bond, as determined by Townes‐Dailey analysis. The NO π‐bond orders show considerable sensitivity to the nature of the para‐substituent, ranging from 0.17 to 0.31. 17O and 15N NMR chemical shifts parallel these changes in π‐bond order.
Computer simulation of lanthanide induced shifts (LIS) in bifunctional substrates. Geometry of europium‐quinone complexes
Authors: Aversa M. C. , Giannetto P. , Saija A.
Published: May 2005

By observing the shifts of the 1H NMR signals of 1,4‐benzoquinones induced by Eu(fod)3, and simulating them with the aid of a novel computer program TWOCEN, it has been shown that the two carbonyl groups of 1,4‐toluquinone and 2,6‐dimethyl‐1,4‐benzoquinone compete in the Eu coordination. The metal binds at two sites on both the carbonyl groups, with 4‐CO having a greater complexing ability with respect to 1‐CO, in line with steric and electronic considerations.
Carbon NMR spectra of conjugated nitrones
Authors: Moskal Janusz , Milart Piotr
Published: May 2005

13C NMR spectra of some bifunctional nitrones containing the aldonitrone functionality as part of the hetero‐1,3‐diene system have been determined, and interpreted for the chemical shifts and coupling constants. The steric structures and long‐range substituent effects on the heteroene carbon resonances are discussed.
Carbon‐13 NMR studies on catechol, phenol and benzene derivatives of biological relevance
Authors: Lai Adolfo , Monduzzi Maura , Saba Giuseppe
Published: May 2005

Some biologically relevant derivatives of catechol, phenol and benzene were studied by 13C NMR spectroscopy. The 13C chemical shifts of the aromatic ring are discussed in terms of the polarizing ability of the substituents.
1H NMR spectra of diastereomeric aromatic dipeptides (Phe‐Phe) in aqueous solution
Authors: Chu Yen‐Ho , Wang Kung‐Tsung
Published: May 2005

The 1H NMR chemical shifts and spin‐spin coupling constants of phenylalanylphenylalanine (Phe‐Phe) dipeptide diastereomers have been completely analysed at 100 MHz. Assignment of the observed signals to individual residue protons is proposed, based on characteristic shifts and standard double resonance experiments. The rotamer populations have also been determined. The spectra of the aromatic regions of the dipeptidyl diastereomers, L‐Phe‐L‐Phe and L‐Phe‐D‐Phe, are very different at pH 1.95 in D2O but similar at pH 9.15 in CD3CND2O (34:66). These results are correlated with the retention behaviour on a C18 reversed‐phase HPLC column.
Study of 1H29Si coupling constants in triethoxysilanes and silatranes by multiple quantum NMR
Authors: Liepinš E. , Birǧele I. , Tomsons P. , Lukevics E.
Published: May 2005

29Si1H coupling constants across two and three bonds in silatranes and model triethoxysilanes were measured from 1H spectra by multiple quantum NMR. There was an increase in the 29SiOCH coupling in the equatorial position and a decrease in that in the axial position of the silicon trigonal bipyramid compared with the tetracoordinated silicon.
Line width considerations in 33S nuclear magnetic resonance of aqueous samples
Authors: Mahendroo Prem P. , Dean Sherry A.
Published: May 2005

A series of sulfur compounds have been examined by 33S NMR at 15.3 MHz. The sharpest resonances were found for the inorganic sulfates, with line widths varying from 3.6 Hz for ammonium sulfate to 9.0 Hz for sodium sulfate. Increasing the viscosity of the solvent did not affect the line widths appreciably. Other anions and molecules examined, and their corresponding line widths, included cysteic acid (30 Hz), sodium thiosulfate (60 Hz), ammonium sulfamate (300 Hz), carbon disulfide (400 Hz), concentrated sulfuric acid (1200 Hz) and dimethyl sulfate (2000 Hz). A comparison of the measured line widths and the spin‐lattice relaxation times, T1, for five of these samples indicated that exchange processes may contribute to and often dominate the 33S resonance line widths in aqueous samples. No signals were observed in concentrated aqueous solutions of cysteine, adenosine monosulfate or chondroitin sulfate after overnight scans.
Conformational equilibria and torsional barriers of the isopropyl groups in N,N‐diiso‐propylbenzamide and its thio and seleno analogues
Authors: Berg Ulf , Pettersson Ingrid
Published: May 2005

The conformations of the isopropyl groups and the barriers to conformational interconversion in N,N‐diiso‐propylbenzamide (1), and its thio (2) and seleno (3) analogues have been studied by dynamic 1H NMR spectroscopy. In 1 only one conformation is observed, whereas 2 and 3 exist as mixtures of three conformations. The use of the strongly deshielding CX (X = O, S, Se) group and comparison with earlier results on similar systems allows total assignment, in the case of 2, rectifying an earlier proposal. The temperature dependence of the NMR spectra of 2 and 3 clearly shows that the E‐ and Z‐isopropyl groups rotate with very different rates, thus providing experimental evidence for the stepwise nature of the conformational interchange.
Structural assignment of the isomeric 2‐ and 4‐endo‐ iodobicyclo[3.3.1]non‐6‐ene‐3‐endo‐ carbonitriles by two‐dimensional 1H and 13C NMR spectroscopy
Authors: Duddeck Helmut , Kaiser Manfred , Brosch Dino
Published: May 2005

The structural assignment of 2‐ and 4‐endo‐iodobicyclo[3.3.1]non‐6‐ene‐3‐endo‐carbonitriles was accomplished by evaluation of their COSY spectra. All 1H and 13C signals were identified unequivocally. Vicinal 1H‐1H coupling constants. NOESY experiments and iodine substituent effects on the 13C chemical shifts show that these molecules prefer the chair conformation.
Determination of the E,Z configuration of alkenephosphonates by the use of vicinal 13C31P coupling constants
Authors: Spassov S. L. , Markova L. , Mondeshka D. M. , Tancheva Ch. N. , Angelov Ch. M.
Published: May 2005

The vicinal 13C31P couplings in the CCCP fragment of alkenephosphonates (∼8 Hz for a cis‐ and ∼22 Hz for a trans‐orientation of the respective nuclei) are a reliable and convenient parameter for the determination of the EZ configuration of these and analogous compounds.
SIMPLE 1H NMR observation of cooperative hydrogen bonding in O‐3′‐sucrose derivatives
Authors: Christofides John C. , Davies David B.
Published: May 2005

Application of the SIMPLE NMR method (secondary isotope multiplet NMR of partially labelled entities) to O‐3′‐sucrose derivatives in DMSO‐d6 solution reveals the presence not only of the 1‐OH Fru…︁‐2‐OH Glu intramolecular hydrogen bond in 3,3′,4′,6′‐tetra‐O‐acety Isucrose, but also of an extensive hydrogen bond network in the glucose residue of 3′,6′‐di‐O‐benzoylsucrose, i.e. 2‐OH…︁3‐OH…︁4‐OH…︁6‐OH.
13C NMR Spectra of 1‐Amino‐1,2,3‐triazole Derivatives. 2—Identification of 4,5‐Unsymetrically Substituted 1‐(N,N‐Diaroyl)amino‐1,2,3‐triazotes
Authors: Rodios Nestor A.
Published: May 2005

The13C NMR spectra of some 1‐(N,N‐diaroyl)amino‐1,2,3‐triazole derivatives are reported. The shifts of the methyl carbons attached to the triazole ring and those of C‐4 and C‐5 of the ring were used to distinguish between 4,5‐unsymmetrically substituted derivatives. The location of a methyl group on the 4‐or 5‐position of the ring can be also deduced from the 1J CH3 value. A complete assignment of the aroyl carbons of the imide moiety is given.
Steric influences on spin‐lattice relaxation rates of methyl protons in substituted aromatic molecules
Authors: Chazin Walter J. , Colebrook Lawrence D.
Published: May 2005

Proton spin‐lattice relaxation rates (R1 values) have been measured at 400 MHz for a series of substituted aromatic compounds to determine the steric effects of ortho substituents on the R1 values of the methyl groups. These values have been interpreted on the basis of differences in the barriers to methyl group rotation caused by the substituent, resulting in changes in the contributions from the dipolar and the spin‐rotation relaxation mechanisms. A significant dynamic range of methyl R1 values has been observed, showing that these measurements are sensitive to the steric environment.
Conformation‐activity relationships in diethylmethyl‐2‐[p‐(o‐alkyloxy‐benzamido)benzoyloxy]ethylammonium bromides in solution as detected by one‐ and two‐dimensional 1H NMR spectroscopy
Authors: Sega Alessandro , Gaggelli Elena , Valensin Gianni
Published: May 2005

The relative conformation of the aromatic rings and the amide bridge of a series of diethylmethyl‐2‐[p‐(o‐alkyloxybenzamido)benzoyloxy]ethylammonium bromides has been established by a combined analysis of non‐selective, single‐selective and double‐selective pulse experiments. Relevant details of the main conformation adopted in solution by the alkyloxy and the diethylmethyl‐2‐benzoylosyethylammonium side‐chains have been obtained by 1H{1H} NOE and 1H two‐dimensional NMR analysis. Molecular Dreiding models were used as a basis of comparison.
Re‐investigation of the conformational interconversion of the 1,2,3,6,7,8‐hexahydropyrene cation radical by EPR, ENDOR and TRIPLE spectroscopy
Authors: Mäkelä Reijo , Vuolle Mikko
Published: May 2005

The conformational interconversion of the 1,2,3,6,7,8‐hexahydropyrene cation radical has been re‐examined by EPR, ENDOR and TRIPLE spectroscopy, and the Arrhenius plot is presented for a wider temperature range than that used earlier. The EPR spectra were measured from 143 to 369 K and the ENDOR spectra from 143 to 263 K. The thermodynamic constants of the conformational interconversion of the cation radical were determined on the basis of the temperature‐dependent spectra. The high‐resolution spectra clearly show that there are two overlapping spectra at low temperature, and this is confirmed by simulation.
Synthetic applications of N–N linked heterocycles. Part 18—substituent effects on the 13C NMR spectra in N‐(4‐Aryliminio‐2,6‐dimethylpyridin‐1‐yl)pyridinium bistetra‐fluoroborates, and some variable‐temperature 1H NMR measurements
Authors: Sammes Michael P. , Ho King‐Wah , Katritzky Alan R.
Published: May 2005

The 13C and 1H NMR spectra have been recorded and fully interpreted for a series of N‐(4‐Aryliminio‐2,6‐dimethylpyridin‐1‐yl)pyridinium bistetrafluoroborates having a variety of phenyl para substituents. Correlations between 13C chemical shifts and both Hammett and Taft dual‐substituent parameters for the aryl substituents were found for C‐2, C‐6, C‐3 and C‐5 of the iminiopyridinyl ring (but not for C‐4), and also for the aryl carbon atom attached to the imino group. Data from variable‐temperature 1H NMR spectra suggest that isomerization about the iminium CN bond is by the little known deprotonation‐imine isomerization‐reprotonation mechanism.
Solute molecular structure determination by NMR: Furan in liquid crystal mixtures
Authors: Jokisaari Jukka , Hiltunen Yrjö , Heikkilä Helena
Published: May 2005

The rα structure of furan dissolved in various thermotropic nematogens and in their mixtures was studied. The results indicate that the structure is not very sensitive to the solvent, contradicting the observations made earlier on the structure of thiophene. The distance ratios and bond angles are observed to be in fair agreement with the results derived from a microwave spectrum.
A 1H and 13C NMR conformational study of methyl‐substituted isochromanes
Authors: Pihlaja K. , Mattinen J. , Kleinpeter E. , Meusinger R. , Duscheck Ch. , Borsdorf R.
Published: May 2005

The 1H and the noise‐decoupled 13C NMR spectra of isochromane and 13 of its methyl‐substituted derivatives were recorded and analysed. The collected data were used to assign the configurations and to determine the position of the conformational equilibria based on the vicinal 1H coupling constants of the aliphatic moiety of the ring system. In some cases the substitution site‐dependent conformational energies of the methyl substituents were also used to estimate the conformer ratios. The primary and some vicinal methyl substituent effects on the 13C chemical shifts of the oxane ring carbons were derived and compared with those of 1,3‐dioxanes. Their usefulness in conformational analysis is demonstrated for 1‐methylisochromane.
Anisotropic solvent‐induced shifts of the trimethylsiloxy group
Authors: Parsonage J. R. , Vidgeon E. A.
Published: May 2005

Polyorganosiloxanes of the QxMy type [Q = SiO4/2; M = (CH3)3SiO1/2] have been quantitatively analysed by 1H NMR in the presence of aromatic solvents. This has been achieved by integrating the signals due to the separation of the chemically equivalent trimethylsilyl protons. This separation is a further example of the ASIS effect (anisotropic solvent‐induced shift). The inverse relationship between observed shift and solute molar volume has been confirmed, and has been extended to include non‐limiting cases. Some evidence for solvent ordering and structure is also presented.
Binuclear lanthanide(III)–silver(I) NMR shift reagents: Investigations of new achiral and chiral analogs
Authors: Wenzel Thomas J. , Ruggles Anne C. , Lalonde Daniel R.
Published: May 2005

A series of new achiral binuclear complexes formed from a ytterbium(III) tris‐beta‐diketonate and silver(I) beta‐diketonate have been evaluated as NMR shift reagents for olefins. The effectiveness of the new reagents was compared with that of similar binuclear reagents that have already been reported. Some unexpected behavior in the form of ‘wrong way’ shifts was observed in the NMR spectrum of substrates in the presence of certain binuclear reagents. Possible explanations for this observation are discussed. A series of new chiral binuclear reagents were evaluated; certain of the complexes with praseodymium(III) resulted in enhanced enantiomeric resolution when compared with previously reported examples. Binuclear complexes formed from Pr(III) tris chelates with the ligands d,d‐dicampholylmethane and 1,1‐difencholylmethane do not appear to be suitable for chiral binuclear shift reagent applications.
Deuterium isotope effects on 13C NMR chemical shifts in 7,12‐dimethylbenz[a]anthracene
Authors: Jones D. W. , Shaw J. D.
Published: May 2005

The 100.6 MHz 13C off‐resonance‐decoupled and polarization‐transfer NMR spectra of 7,12‐dimethylbenz[a]anthracene and its 5‐deuteriated analogue in deuteriated chloroform solution enabled assignments of the shifts of C‐3 and C‐5 to be revised, and other spectral ambiguities to be reduced. Negative, i.e. upfield, deuterium‐induced secondary isotope shifts, Δδ = δ(C…︁D) – δ(C…︁H), were evident over one, two, three and four bonds and, also, small apparently significant positive shifts to the methyl carbons at the 7‐ and 12‐positions, i.e. over five and six bonds, respectively. 13C1H coupling constants were unaffected by the deuteriation.
Differences and sums of traces within, COSY spectra (DISCO) for the extraction of coupling constants: ‘Decoupling’ after the measurement
Authors: Kessler H. , Müller A. , Oschkinat H.
Published: May 2005

A procedure is proposed for obtaining coupling constants from phase‐sensitive H,H‐COSY spectra. For this purpose, firstly pseudo‐one‐dimensional spectra are created by co‐addition of individual traces of cross‐peaks, and by a similar addition of diagonal peaks in a spectrum which is phase corrected to pure‐absorption line shapes. The sum and difference of the pseudo‐one‐dimensional spectra of a cross‐peak and its diagonal peak give two spectra, with a pattern in which the active coupling ceases to exist (‘spin decoupling’) but is shifted by half the value of the same. If diagonal peaks are not available owing to overlapping signals, sums and differences of the pseudo‐one‐dimensional spectra of two cross‐peaks can be applied to simplify spectral patterns for the evaluation of J values. The procedure is demonstrated with the example of the AMXY spin system of a tyrosine, and the complex pattern of the Pro8 spin system of the cyclic decapeptide antamanide. The conformation of the Pro8 ring, derived from the coupling constants thus obtained, is of the γE type.
Hydrogen‐bonded 2‐hydroxybenzalazines: Complete assignment of 1H and 13C NMR spectra
Authors: Meléndez Enrique , Serrano José Luis , Sánchez‐Ferrando Francisco
Published: May 2005

The 80 MHz 1H NMR and 20 MHz 13C NMR spectra of eleven substited benzalazines (subsituenst: α‐methyl, α,α′‐dimethyl, 2‐hydroxy, 2,2′‐dihydroxy, 4‐n‐octyloxy, 4,4′‐di‐n‐octyloxy) possessing mesogenic acivity have been assigned using a variety of one‐dimensional techniques. These include homonuclear NOE measurements, selective heteronuclear 13C{1H} NOE difference spectroscopy, singlefrequency off‐resonance decoupling, spin—echo multiplicity sorting (SEFT) and long‐range heteronuclear coupling constant determintion via both gated decoupling and selective excitation (DANTE).
Configuration and conformation of some 4‐hydroxy‐cis‐ and ‐trans‐1‐oxadecalins
Authors: Dolmazon René , Gelin Suzanne
Published: May 2005

The configuration and conformation of some diastereomeric 4‐hydroxy‐cis‐ and ‐trans‐1‐oxadecalins were inferred by 1H and 13C NMR spectroscopy. The results obtained indicate that the cis‐fused compounds are conformationally homogeneous, having the oxygen atom attached to the cyclohexyl ring in the axial position. In the 13C NMR spectra, the magnitude of the α and γ substituent effects of the hydroxy group is rationalized in terms of steric deformations of the tetrahydropyran ring.
Intrinsic ASIS of the methyl protons of camphor
Authors: Bertran Jose Fernández , Rodriguez Mario rodríguez
Published: May 2005

The intrinsic ASIS of the C‐8, C‐9 and C‐10 methyl protons of camphor in 14 hydrocarbon solvents have been calculated using intrinsic ASIS values of the TMS protons. The intrinsic ASIS of the methyl groups show excellent correlation among themselves and, therefore, can be factored into independent solute and solvent factors UiVα. The solute factors, Ui, depend on the position of the methyl group with respect to the polar carbonyl group. The solvent factors, Vα, correlate with the benzene ring concentration of the aromatic solvents measured by d/M, which is in accordance with a general solvation mechanism but not with the formation of specific solute‐solvent complexes.
NQR and NMR study of pseudorotation in solids
Authors: Kibrik G. E. , Kjuntsel I. A. , Kozlov E. S. , Mokeeva V. A. , Soifer G. B.
Published: May 2005

Nuclear quadrupole resonance and nuclear magnetic resonance methods have been used to study the pseudorotation process in solids. In crystalline dimeric (Hal3PNR)2phosphazo compounds, where Hal = CI or F, and R contains protons, the temperature dependences of the35CI,19F and1H spectra and the relaxation times indicate intramolecular exchange of the ‘trigonal twist’ type between one axial and two equatorial halogen atoms attached to the pentacoordinated phosphorus. The activation energy,Ea, for the exchange process is obtained from theT1temperature dependence of the35CI nuclei and from theT1etemperature dependence of the19F and1H nuclei. In the case of chlorinated phosphazo compounds,Ea, lies in the 59‐105 kJ mol−1range, whereas in solid (F3PNCH3)Ea, is about 38 kJ mol−1.
Carbon‐13 and mercury‐199 NMR data for methyl‐substituted bisaryl mercury compounds
Authors: Rowland K. E. , Thomas R. D.
Published: May 2005

13C and 199Hg NMR data are reported for seven bisaryl mercury compounds (aryl = phenyl, o‐tolyl, m‐tolyl, p‐tolyl, 2,5‐xylyl, 2,6‐xylyl and mesityl) and two unsymmetrically substituted compounds, phenyl(o‐tolyl)‐and phenyl(m‐tolyl)‐mercury, in deuteriochlorform. Also presented are carbon chemical shift substituent parameters due to mercury substitution on the aromatic ring.
13C NMR spectra of wyosine, a hypermodified nucleoside of transfer RNAs, and related compounds
Authors: Golankiewicz Bożenna , Folkman Wojciech
Published: May 2005

Complete 13C NMR spectral assignments were made for wyosine, 4,9‐dihydro‐4,6‐dimethyl‐9‐oxo‐3‐(β‐D‐ribofuranosyl)imidazo [1,2‐a]purine, a hpermodified, fluorescent nucleoside of transfer RNAs, and its isomers methylated at N‐5 and at N‐1. The influence of the position of N‐methylation on the 13C chemical shifts of the tricyclic nucleoside is discussed. In relation to the parent N‐unsubstituted compound, the most pronounced changes of chemical shifts appear in wyosime. Chemical shift data for the sugar moiety suggest that the population of the anti conformer in wyosine is higher than in the other tricyclic nucleosides.
13C NMR Spectra and the stereochemistry of the adducts of enaminones with P‐benzoquinone
Authors: Kozerski Lech
Published: May 2005

1‐Alkylamino‐2‐alkyloylpropenes give, with ρ‐benzoquinone, derivatives of 2H‐1,5‐benzodioxepine, 2‐phenylenamine and 2,3‐dihydrobenzo[b]furan. 13C NMR spectra were used to establish the primary structures and stereochemistry of the reaction products, which were verified by x‐ray analysis for several (Z)‐2,3‐dihydrobenzofurans. The data show the usefulness, for diastereomeric distinction, of the low‐frequency shifts induced for the chemical shifts of aliphatic or aromatic 13C nuclei by an eclipsed nitrogen in a 1,4‐arrangement.
Carbon‐13 NMR study of acridine derivatives: 13C chemical shifts of some new 9‐alkylthioacridines and 9‐alkylthio‐1,2,3,4‐tetrahydroacridinium salts
Authors: Faure R. , Poulallion P. , Galy J. P. , Giovanangelli G. , Soyfer J. C. , Barbe J.
Published: May 2005

Thirty‐five new 9‐alkylthioacridines and 9 ‐ alkylthio ‐ 1,2,3,4 ‐ tetrahydroacridinium salts were studied by 13C NMR spectroscopy and their chemical shifts are reported.
Calculation of 1H chemical shifts of conjugated alternant hydrocarbons with (4m) rings
Authors: Vogler H.
Published: May 2005

The 1H chemical shifts of the polycyclic alternant hydrocarbons bicyclo[6.2.0]decapentaene, cycloocta[def]biphenylene, dicycloocta[1,2,3,4‐def: 1′,2′,3′,4′‐jkl]biphenylene and cycloocta[1,2,3,4‐def]benzo[3,4]cyclobuta[6,7]biphenylene, which contain an 8‐membered ring, are calculated by means of a semi‐empirical approach. The agreement between experimental and calculated shifts is good if geometries are determined by a self‐consistent resonance integral, or even better by a π‐SCF force field procedure. Predictions are made for the as yet unknown dianions of these hydrocarbons.
Multidimensional spectroscopy
Authors: Bremser Wolfgang , Fachinger Winfried
Published: May 2005

Intelligent programs for structure elucidation should be able to predict structural features, or even complete structures, for an unknown compound. This can be accomplished by substructure analysis of the topological matrices corresponding to the most similar reference spectra detected by a library search. A comparison of the results from different spectroscopic techniques (1H NMR, 13C NMR, IR, MS) reflects the content of the individual data bases, and also the sensitivity of the specific physical experiment to structural changes. The results can be combined to yield multidimensional information on the probability of any given substructure, even without crosslinked libraries from varying sources. In connection with the structure generator and the 13C NMR spectrum estimation in ACCESS, a prediction of novel structures is routinely possible, as exemplified by the analysis of the spectra of 3′‐methylacetophenone and genipin. The great advantages of this approach lie in its high flexibility in omitting or adding information and the absence of hand‐encoded rules, because knowledge of the system simply stems from its experience, i.e. the structure‐oriented spectral data bases.
Solid‐state tin‐119 NMR spectroscopy: The first observations of (Tin‐119, tin‐117) coupling constants
Authors: Harris Robin K. , Mitchell Terence N. , Nesbitt Geoffrey J.
Published: May 2005

(Tin‐119, tin‐117) coupling satellites are visible in the CP/MAR spectra of tetrakis(trimethylstannyl)methane and of a series of tetrastannacyclohexanes, the values in the solid and solution states being equal within experimental error. The single signal from the former compound has a line width of only 28 Hz. The broad lines (Δν1/2 320 Hz) obtained for 1,4‐bis(trimethylstannyl)benzene precluded the observation of 5J(SnSn).
1H and 13C chemical shift data of two sulphonaphthoimidazoles
Authors: Parrilli M. , Pastore A. , Temussi P. A.
Published: May 2005

1H and 13C chemical shifts are reported for the condensation products of 1‐amino‐2‐phenylazonaphthalene‐4‐sulphonic acid with benzaldehyde and trans‐cinnamaldehyde, two model compounds for sweetening agents. Assignments, based on several two‐dimensional techniques, confirm the naphthimidazole skeleton for both compounds.