bluuebunny/crossref_metadata_2025 huggingface dataset:
Die Ermittlung der Beständigkeit gegen Spannungsrißkorrosion (SpRK) von hochlegierten Sonderstählen in chloridhaltigen wäßrigen Medien
Authors: Brücken Volker , Rockel Manfred B.
Published: May 2005

Die nichtrostenden Stähle auf Basis 18 Cr 10 Ni(Mo) sind durch Höherlegieren mit Cr, Ni und Mo weiterentwickelt worden. Das Spannungsrißkorrosionsverhalten dieser hochlegierten Stähle wurde in praxisnahen Prüfmedien ermittelt, da die Beständigkeit gegenüber Spannungsrißkorrosion (SpRK) teilweise noch ungeklärt ist. SpRK‐Versuche an Bügelproben in siedender 62%iger CaCl2‐Lösung ergaben eine gute Differenzierung in Abhängigkeit vom Ni‐ und Mo‐Gehalt. Mit zunehmendem Ni‐Gehalt wird die SpRK‐Anfälligkeit der Sonderstähle zu längeren Standzeiten verschoben, wobei Legierungen mit ≧ 42‐Masse% Nickel beständig sind. Sonderstähle mit hohem Molybdängehalt verhalten sich gegenüber Stählen mit niedrigem Molybdängehalt SpRK‐resistenter. Diese Ergebnisse konnten an Rundzugproben unter konstanter Last und potentiostatischen Bedingungen in siedender 62% CaCl2‐Lösung bestätigt werden. Die an den Sonderstählen mit 25% Ni und an den Ni‐Basislegierungen registrierten Freien Korrosionspotentiale liegen in dem potentiostatisch ermittelten SpRK‐unempfindlichen Bereich. Der hochmolybdänhaltige Sonderstahl X 2 NiCrMoCu 25 20 6 (1.4529) weist das gleiche sehr anodisch liegende kritische SpRK‐Potential auf wie die Ni‐Legierung NiCr 21 Mo (2.4858). Der Superferrit X 1 CrNiMoNb 28 4 2 (1.4575) und der austenitisch‐ferritische Stahl X 2 CrNiMoN 22 5 (1.4462) zeigten in beiden Versuchen das entsprechend vom Stahl X 10 CrNiMoTi 18 19 (1.4571) bekannte ungünstige SpRK‐Verhalten. Untersuchungen in siedender 4 m NaCl (Erlenmeyerkolben) ergaben auch unter verschärften Versuchsbedingungen aufgrund der Versuchsanordnung keine SpRK. Der große Einfluß des Sauerstoffgehaltes wurde in Autoklavenversuchen mit definierten Sauerstoff‐ und Chloridkonzentrationen nachgewiesen. Die SpRK‐Beständigkeit der Stähle nimmt bei Luftsättigung (8 … 10 ppm O2) ab, wobei die Chloridkonzentration (200 und 2000 ppm Cl−) keinen wesentlichen Einfluß ausübt. Bügelproben sollten bei SpRK‐Untersuchungen den Erichsenproben vorgezogen werden. Metallographisch und rasterelektronenmikroskopisch konnten die für die SpRK charakteristischen Bruchmerkmale festgestellt werden.
Elektrochemische Methode zur Prüfung des Korrosionsverhaltens austenitischer CrNiMo‐Stähle im Schweißnahtbereich
Authors: Voigt C. , Riedel G. , Werner H.
Published: May 2005

Schweißverbindungen von austenitischen CrNiMo‐Stählen können durch Seigerungen und Ausscheidungen in der Wärmeeinfluß‐, Hochtemperaturzone und im Schweißgut gegenüber dem Grundwerkstoff loch‐ und spaltkorrosionsanfälliger sein.

Geeignete Prüfmethoden sind zur Optimierung von Schweißtechnologien notwendig. Eingeführt sind Potentialvergleiche aus Potential‐Weg‐Kurven (DIN 50 919), Vergleich kritischer Lochkorrosionstemperaturen in FeCl3‐ oder anderen Modelllösungen, visuelle Beurteilung nach Dauerbelastungstest mit oder ohne elektrochemischer Belastung.

Vorgestellt wird eine kleine Aufsatzmeßzelle mit Rückseitenheizung und zirkulierendem und temperierbarem Elektrolyten, mit Hilfe derer einzelne Bereiche einer Schweißnaht elektrochemisch belastet werden können.

Getestet werden Schweißverbindungen von Werkstoffen X2CrNiMoN 17 12 2 (1.4406), X2CrNiMoN 17 13 5 (1.4439) und X1NiCrMoCu 31 27 4 (2.4563) in sauren NaCl‐Lösungen im Bereich 25–75°C. Grenzpotentiale der Lochkorrosion werden abgestuft für Grundwerkstoff, Wärmeeinflußzone und Schweißgut erhalten. Ein Einfluß der Streckenenergie ist angedeutet, statistisch aber nicht gesichert.
Dimethyl ether chemical ionization mass spectrometry
Authors: Burrows Elizabeth P.
Published: May 2005

The uses of dimethyl ether (DME) as an unusual positive ion reagent for chemical ionization mass spectrometry (CIMS) are reviewed. The fragment–molecule adducts formed by ion–molecule reactions of organic substrates with the ionized gas are highly characteristic for the substrates and frequently can be used to differentiate among isomers. The fragmentation mechanisms of the adducts have been studied by collision‐induced dissociation and with deuterium labeling, and, in some cases, are well‐understood. DME CIMS has been applied to a wide variety of classes of organic compounds, including substituted aromatics, amino alcohols, lactones, lactams, polyethylene glycols, benzodiazepines, azepines, trichothecenes, and certain alkaloids, nucleoside antibiotics, and polynuclear aromatic hydrocarbons. © 1996 John Wiley & Sons, Inc.
Cover Picture: Macromol. Theory Simul. 4/2005
Authors: Wang Rong , Hu Jinglei , Jiang Zhibin , Zhou Dongshan
Published: May 2005

Cover: There are at least twelve structures found in the melt of linear ABCD tetrablock copolymers based on two‐dimensional self‐consistent field theory. The pictures on the cover show four morphologies largely different from those of diblock and triblock copolymers. The microphase patterns, displayed in the form of density, are shown in red, green, blue and white, assigned to A, B, C, and D, respectively. The upper two morphologies “four‐color” lamellae and “three‐color” core‐shell hexagonal phase prove the existing experimental observations. Further details can be found in the Full Paper by R. Wang,* J. Hu, Z. Jiang, and D. Zhou on page 256.
Verschleiß bei gleichzeitiger elektrochemischer Beanspruchung: Korrosionsverschleiß
Authors: Wiegand H. , Broszeit E. , Hirth F. W. , Speckhardt H.
Published: May 2005

Es wird über erste Versuche aus dem Gebiet des Korrosionsverschleißes berichtet, die durch Schadensfälle in der Praxis angeregt wurden. Das Besondere dabei scheint zu sein, daß man bisher der kombinierten mechanisch‐chemischen Beanspruchung auf dem Gebiet des Verschleißes zu wenig Aufmerksamkeit geschenkt hat, so daß durch Korrosionsverschleiß hervorgerufene Schäden häufig nicht als solche erkannt werden, sondern ihre Ursachen nur in einem mechanischen Verschleiß (abrasiv oder adhäsiv) oder unter Umständen noch in einem chemischen Angriff gesehen werden.
Plattiertes Grobblech mit Titan‐Auflage
Authors: Pircher H. , Pennenkamp R. , Sussek G.
Published: May 2005

Die Arbeit befaßt sich mit Fragen der Herstellung sowie den Verarbeitungs‐ und Gebrauchseigenschaften von plattierten Grobblechen. Erörtert werden die wesentlichen Merkmale von Sprengplattierungen, u. a. wird über Versuche mit höherfestem Titan der Gruppe II berichtet.

Großformatige Bleche mit Titan‐Auflagedicken von 1,5 bis 3 mm werden über einen neuentwickelten Fertigungsweg durch Warmwalzen von sprengplattiertem Halbzeug hergestellt. Mit Warm‐ und Kaltumformungen, Untersuchungen zum Korrosionsverhalten sowie der erfolgreichen schweißtechnischen Erprobung wird gezeigt, daß die neuartige Plattierung den Anforderungen bezüglich der Verarbeitbarkeit voll genügt.
Identification of chemical warfare agent in air samples using capillary column gas chromatography with three simultaneous detectors
Authors: Kaipainen Antti , Kostiainen Olli , Riekkkola Marja‐Liisa
Published: May 2005

An identification method for chemical warfare agents using a capillary column gas chromatograph equipped with a thermal desorption cold trap injector and three different detectors is describ ed. The most reliable identification parameters were the retention indices. The relative photoinonization detector/flame ionization detector response ratios normalized to aniline gave additional information about all compounds, whereas the response ratios calculated for the thermionic flame ionization and thermionic photo‐ionization detection gave reliable results only for the nerve agents soman and tabun.
The need for levodopa as an end point of Parkinson's disease progression in a clinical trial of selegiline and α‐tocopherol
Authors: LeWitt Peter , Oakes David , Cui Lu ,   The Parkinson Study Group
Published: May 2005

Progression of Parkinson's disease (PD) can be detected through changes in clinical ratings or disability assessments. A clinical trial, Deprenyl and Alpha‐Tocopherol Antioxidative Therapy of Parkinsonism (DATATOP), used a novel study end point: increase in parkinsonian disability to the extent that investigators determined the need for treatment with levodopa. We analyzed DATATOP results to learn if this operationally defined end point could be reproduced from elements of the Unified PD Rating Scale (UPDRS) and other conventional clinical scales. Our analysis involved UPDRS, Schwab and England Activities of Daily Living (S‐E ADL), and Hoehn andYahr (H‐Y) scores when DATATOP subjects reached the study end point. Various UPDRS components were examined, including subscores measuring severity of impaired ADL, bradykinesia, postural instability and gait difficulty, tremor, and rigidity. Data from subjects reaching the end point were compared with assessments of those DATATOP subjects who did not, matched for the same duration of enrollment. All measures showed subjects who reached the end point had significantly greater mean impairment than did controls, although the two groups had substantial overlap. Multivariate analysis by using conditional logistic regression suggested that the end point was determined more by functional (S‐E ADL and the UPDRS ADL scores) than by clinical examination criteria. The method of classification and regression trees suggested a simple decision tree splitting, respectively, on S‐E ADL, UPDRS ADL, H‐Y score, and UPDRS ADL again, with an estimated overall misclassification probability of 18%. We conclude that the DATATOP end point cannot be fully reproduced from the traditional clinical measures, although it can give results that are consistent with these scales in a well‐designed clinical trial.
15N NMR spectra of pyrimidine and [1,3‐15N2]pyrimidine
Authors: Adams C. M. , Von Philipsborn W.
Published: May 2005

The fully proton‐coupled 15N NMR spectra of pyrimidine with natural isotope abundance and of bis‐labelled [1,3‐15N2]pyrimidine, obtained using single pulse experiments, are described. The 15N and 1H spectra are analysed for 2J, 3J and 4J(NH) as well as N,N and H,H coupling constants.
A quantitative empirical treatment of 13C NMR chemical shift variations on successive substitution of methane by halogen atoms
Authors: Gasteiger Johann , Suryanarayana Iragavarapu
Published: May 2005

The 13C NMR chemical shifts of halogen‐substituted methanes are reproduced by a linear two‐parameter equation. The parameters consist of the charge on the carbon atom, as calculated by iterative partial equalization of orbital electronegativity, and the square of the mean molecular polarizability.
Substituent effects on 13C chemical shifts of 1‐arylsulphonyl‐2‐arylaziridines
Authors: Knipe A. C. , Khandelwal Y. , McAuley I. E. , Brown N. M. D.
Published: May 2005

Carbon‐13 chemical shifts of 1‐phenylsulphonyl‐2‐phenylaziridine and several of its m‐ and p‐substituted derivatives have been determined. The substituent chemical shift (SCS) effects on the benzylic carbon C‐2, and on the methylene carbon C‐3 have been satisfactorily correlated with Hammett substituent parameters (δ) for variation of the C‐2‐aryl ring substituent (with a fixed arylsulphonyl ring), and for analogous variation of the arylsulphonyl ring (with a given C‐2‐aryl ring). The results reveal an inverse C‐2‐aryl SCS effect on C‐2, whereas the effect on C‐3 is normal; substituents on the arylsulphonyl ring have a normal effect on both C‐2 and C‐3, for which the SCS is to higher frequency with increasing electron‐withdrawing power of the substituent.
Solvent and Temperature Effects on One‐Bond Spin‐Spin Coupling Constants
Authors: Barna Jennifer C. J. , Robinson Michael J. T.
Published: May 2005

Intrinsic solvent and temperature effects on 1J(CX) (X = H, C, F) have implications for users of one‐bond couplings in conformational analysis.
Investigation of Benzimidazoles. 5—transmission of the substituent effects in 2‐substituted 5(6)‐nitrobenzimidazoles studied by 1H, 13C and 15N NMR spectroscopy
Authors: Lopyrev V. A. , Larina L. I. , Vakul'skaya T. I. , Larin M. F. , Shibanova E. F. , Titova I. A. , Voronkov M. G. , Liepin'sh E. E.
Published: May 2005

The influence of substituents on the 1H, 13C and 15N NMR chemical shifts of 2‐substituted 5(6)‐nitrobenzimidazoles and their analogues labelled with 15N in the nitro group was investigated. It was found that the substituent effects are transmitted to the carbon and hydrogen nuclei in positions 4–7 mainly by the resonance mechanism, but to the nitro‐nitrogen atom with approximately equal contributions from the resonance and inductive components. Comparison of the transmission of substituent effects in nitro‐benzimidazoles with para and meta derivatives of nitrobenzene showed that the nitro group seems to be more tightly conjugated with the benzimidazole fragment than with the benzene ring.
An equation utilizing empirically derived substituent constants for the prediction of vicinal coupling constants in substituted ethanes
Authors: Colucci William J. , Jungk Steven J. , Gandour Richard D.
Published: May 2005

A simple equation has been developed for the prediction of vicinal coupling constants in HCCH fragments:

The equation is a cosine series in θ, the torsion angle between vicinal hydrogens. The feature which distinguishes this equation from similar equations is the inclusion of δSi terms, which describe the magnitude of each substituent's effect. These substituent constants have been defined from experimental data. An orientation effect which is dependent on the torsion angle(s) between substituent(s) and a vicinal hydrogen is included. Substituent constants have been defined for 39 groups, of which 15 have been experimentally determined herein. The parameters for the equation have been defined from 49 torsion angles in 19 conformationally rigid compounds. The torsion angles have been determined from x‐ray crystal structure data and molecular mechanics calculations. The multiplicity of structures used to determine the substituent constants should allow for the application of this equation to a wide variety of structures.
1H NMR and IR spectra of antitumour anthracyclines: Effect of the substitution pattern on the chemical shift values of the phenolic protons and on IR absorptions of the quinone system
Authors: Vigevani Aristide , Ballabio Marzia , Gandini Elena , Penco Sergio
Published: May 2005

1H NMR and IR data of numerous natural and synthetic analogues of daunorubicin and doxorubicin, anthracycline antibiotics successfully used in the clinical treatment of human tumours, have been recorded. The chemical shift values of the phenolic protons of approximately 130 compounds are reviewed and discussed with the aim of establishing a relationship between δ values and structural features. The IR absorptions of the quinone system in the region 1560–1680 cm−1 are also examined.
Increments for calculation of the 13C NMR shifts of acetylated polyphenols considering steric interactions
Authors: Wegner‐Hambloch S. , Glombitza K.‐W.
Published: May 2005

Considerable deviations in the values obtained are an inherent deficiency in the calculation of 13C NMR chemical shifts of the polyphenolic phlorotannins from brown algae when using increments for monosubstituted aromatic substances. In order to account for steric interactions within this class of compounds, special increments have been developed by the use of multiple linear regression with dummy variables. With these 13C NMR chemical shift increments, the occurrence of known and of hitherto unknown substitution patterns can be predicted.
NMR Spectral Analysis of Tetrahydro‐2‐( 3,4 ‐dimethoxyphenyl)‐4‐[(3,4‐dimethoxyphenyl)methyl]‐3‐furanmethanol, a Dimethyl Ether of Lariciresinol, from Monechma ciliaturn
Authors: Maat L. , Peters J. A. , Linders J. T. M. , Hussein Ayoub S. M.
Published: May 2005

Tetrahydro‐2‐(3,4 ‐dimethoxyphenyl)‐4‐[(3,4‐dimethoxyphenyl)methyl]‐3‐furanmethanol has been isolated from Monechrna ciliaturn. Its structure was deduced from the 200 MHz 1H NMR spectrum.
Carbon‐13 NMR studies of oxazolidines, N‐borane‐oxazolidines and oxazolidinium salts derived from pseudoephedrine: Steric effect of the BH3 and CH3 groups on the chemical shifts
Authors: Paz‐Sandoval M. A. , Santiesteban F. , Contreras R.
Published: May 2005

Carbon‐13 NMR chemical shifts in various oxazolidines derived from pseudoephedrine and their corresponding N‐borane adducts and oxazolidinium salts are examined. The observed shifts can be rationalized on the basis of steric factors, owing to the similarity between the borane adducts and the oxazolidinium salts, i.e., BH3 and CH3 appear to have the same substituent effects.
Aryl carbon chemical shifts of methylbenzoic acids and methylbenzoate anions
Authors: Guilleme Joaquin , Diez Ernesto , Bermejo Francisco J.
Published: May 2005

The aryl carbon chemical shifts of methylbenzoic acids in CDCl3 and methylbenzoate anions in aqueous NaOH solutions have been assigned. The shifts have been interpreted by means of a model based on the additivity of substituents which is similar to that previously developed for the analysis of the methyl chemical shifts. Corrective parameters included to take into account the interactions of adjacent substituents are found to be related to both the twist angle, θ, of the carboxyl or carboxylate substituents and the conformation of the methyl groups. The derived values of the twist angle are in closer agreement with x‐ray data than those estimated from UV spectra or from Cl‐PPP computations.
13C NMR spectra of plucheinol and its ester derivatives
Authors: Arriaga F. J. , Borges‐Delcastillo J.
Published: May 2005

13C NMR data are presented for plucheinol and its ester derivatives obtained from Pluchea odorata (L) Cass. A comparison with the data reported for cuauhtemone derivatives was carried out. An unexpected deshielding for C‐4 in diester derivatives was observed.
Conformational analysis of N‐acylazabicyclooctanes
Authors: Sohár P. , Pelczer I. , Váczi I. , Tombor A. , Matolcsy G.
Published: May 2005

N‐Acyl derivatives of 1,3,3‐trimethyl‐6‐azabicyclo[3.2.1]octane were synthesized as compounds with potential pesticidal activity. The conformation of the starting compound and the substituent dependence of the amide rotamers of the acyl derivatives were studied by 1 and 13C NMR spectroscopy, making use of solvent effects (ASIS) and DR, DNOE and DEPT measurements.
Halogenated epoxides 8—13C NMR data of ring halogenated oxiranes
Authors: Spraul M. , Keul H. , Pfeffer B. , Hähnle J. , Griesbaum K.
Published: May 2005

The 13C NMR data of 42 ring‐halogenated oxiranes containing fluorine, chlorine, bromine and, in one case, iodine as substituents are reported and discussed with respect to the influence of the halogen and of other substituents on the chemical shifts of the ring carbon atoms. For monocyclic mono‐ and dichlorooxiranes increments have been determined which allow the calculation of the chemical shifts of the ring carbon atoms. Comparison of the 13C NMR data of substituted 1,2‐dihaloethylenes with those of the corresponding epoxides showed that the signals of the ring carbon atoms of the halogenated oxiranes always appeared at considerably higher field than those of the sp2 hybridized vinylic carbons in the respective precursors.
Simplified measurement of lanthanide‐induced shifts
Authors: Raber Douglas J. , Peters Joop A.
Published: May 2005

A simplified procedure is presented for the determination of accurate lanthanide‐induced shifts. Experimental and simulated data are used to show that bound shifts for both 1:1 and 1:2 complexes with shift reagent can be obtained with as few as six or seven different lanthanide: substrate concentration ratios. This represents a substantial saving in experimental effort over the 25 different concentration ratios that were used previously for this method. The modified procedure affords accurate results if care is taken to minimize experimental errors, and if data are obtained over a wide range in the fraction of substrate that is complexed.
NMR Spectroscopy of platinum(II)‐8‐substituted quinoline complexes. nJ(PtH) Coupling Constants and Pt…︁HC Interactions
Authors: Anklin C. G. , Pregosin P. S.
Published: May 2005

A series of complexes of composition trans‐[PtCl2L(PEt3)], where L is an 8‐substituted quinoline, have been studied by 1H and 31P NMR spectroscopic methods [substitnent = CHO, CH3, HC(CH3)2, CHBr2]. The protons of the substitnent at the 8‐position couple to 195Pt with values for nJ(195Pt1H) which are too large for five‐bond coupling constants, thereby suggesting a Pt…︁HC interaction. Two‐dimensional 1H NMR methods were used for purposes of assignment and also for defining a chemical exchange process. The shape of the 195Pt satellite lines in the 1H spectra vary with the magnetic field strength owing to CSA relaxation of the 195Pt.
Residually coupled attached proton test in the 13C NMR assignment of natural products
Authors: Crews Phillip , Naylor Steve , Myers Barbara L. , Loo James , Manes Lawrence V.
Published: May 2005

Attached proton test (APT) spectra acquired with residual coupling (termed RECAPT) can be advantageous in assigning 13C NMR spectra of complex natural products. RECAPT was applied to the analysis of the 13C NMR spectra of two terpene marine natural products to illustrate its advantages over APT in situations where peaks are accidentally degenerate, or where large J(CH) values give misleading phase APT peaks.
Electron–nuclear double resonance (ENDOR) studies of neutral odd–alternate aromatic hydrocarbon free radicals formed by thermal dissociation
Authors: Lewis I. C. , Singer L. S.
Published: May 2005

Electron–nuclear double resonance (ENDOR) spectra are presented for the odd‐alternate aromatic hydrocarbon neutral radicals phenalenyl, [2H5]phenylphenalenyl and for the benzo[c,d]pyrenyl and benz[d,e]anthracenyl radicals formed by thermal dissociative processes in solution. Proton hyperfine coupling constants were determined from the ENDOR spectra and were shown to give an excellent linear correlation with McLachlan spin densities with Q = −26.5 G.
An investigation of the tautomeric equilibria of some 3‐hydroxyindazole derivatives by 15N NMR spectroscopy
Authors: Schilf W. , Stefaniak L. , Witanowski M. , Webb G. A.
Published: May 2005

15N NMR shielding data are reported for six 3‐hydroxyindazole derivatives and compared with the results of INDO/S‐SOS shielding calculations which are used for assignments. The position of tautomeric equilibrium was found to be solvent dependent and to be proportional to the Gutmann acceptor number of the solvent employed.
Application of 15N NMR to a quantitative investigation of tautomerism in some thiolopyridines
Authors: Stefaniak L. , Webb G. A. , Brevard C. , Bourdonneau M. , Lejeune R. , Thunus L. , Lapière C. L.
Published: May 2005

15N NMR shielding measurements are reported for a series of derivatives of some thiolopyridines. The results obtained are used to provide quantitatively reliable estimates of three tautomeric equilibria involving the pyridine nitrogen atom.
13C nuclear magnetic resonance spectra of amaryllidaceae alkaloids. I—alkaloids with the crinane skeleton
Authors: Frahm August W. , Ali Ahmed A. , Ramadan Mahmoud A.
Published: May 2005

The13C NMR spectra of 15 Amaryllidaceae alkaloids with the crinane skeleton were measured and the chemical shifts unequivocally assigned. From the derived specific shift ranges, it is possible to establish both the complete oxygenation pattern of the 5, 10b‐ethanophenanthridine skeleton and its stereochemical arrangement.
Substituent effects on 1H NMR spectra of 4‐and 4′‐substituted tras‐N‐benzylideneanilines in acidic solution
Authors: Odian George , Yang Nan‐Ioh , Wei Yen
Published: May 2005

Various 4‐ and 4′‐substitued trans‐N‐benlizylidenanilines were synthesized and their 1H NMR spectra recorded at 30 °C in DMSO‐d6, and acidic media (TFA‐d and D2SO4). The effects of substituents on the chemical shifts of H‐α (proton on carbon of imine group) and H‐2′ (protons on benzaldehyde ring ortho to the imine group) were analysed by the Hammett single parameter and Taft dual substituent parameter (DSP) techniques. In the neutral solvent DMSO‐d6, there is transmission of the electronic effects of substituents on the benzaldehyde ring to the H‐α and H‐2′ protons, but no electronic transmission for substituents on the aniline ring. There is a dramatic change in acid media. Protonation of the imine group results in significant electronic transmission from substituents on the aniline ring to the H‐α and H‐2′ protons, as well as an enbancement in electronic transmission from substituents on the benzaldehyde ring. DSP analysis indicates that both inductive and resonance factors are responsible for the observed electronic transmission effects, with resonance being the major factor.
Analysis of the proton, carbon, and nitrogen NMR spectra of cis,cis‐ and cis,trans‐1,3,5‐triaminocyclohexane
Authors: Yu Chin , Dumoulin Charles L. , Levy George C.
Published: May 2005

The proton spectrum of the isomeric mixture of cis,cis‐ and cis,trans‐1,3,5‐triaminocyclohexane was assigned with a 2D COSY experiment. Using Forrest's modified equation and the 2D J spectrum results, the conformations of the two isomers were analysed. The six‐membered ring of the cis,trans isomer is flattened by 1,3‐diaxial interactions between two amino substituents; in the cis,cis isomer, ring pucker is increased owing to non‐bonded interaction between the equatorial amino groups and adjacent methylene protons. The 13C and 15N spin—lattice relaxation of the two isomeric 1,3,5‐triaminocyclohexanes was also measured at different pH values; NHx groups rotate faster with decreasing pH. Rotation/jump rates and barriers are reported, determined from the NT1DD ratios between 15N and 13C nuclei.
Endor studies of cation radicals from pharmacologically active phenothiazines
Authors: Helle N. , Kurreck H. , Bock M. , Kieslich W.
Published: May 2005

A variety of substituted phenothiazine cation radicals, including those from pharmacologically active derivatives, e.g. chlorpromazine, alimemazine and laevomepromazine, have been studied by means of ENDOR and TRIPLE resonance spectroscopy. These techniques allowed accurate determinations of hyperfine coupling constants, including their signs. Conclusions concerning molecular structure (e.g. twist angles) could be drawn, supporting previous investigations of the interrelationship of molecular conformations with the pharmacological potential, i.e. neuroleptic, antihistaminic or anti‐Parkinsonian.
Measurement of long‐range heteronuclear selective 13{1H} NOE enhancements: 4‐ (α‐arylethylidene)‐2‐phenyl‐5(4H)‐oxazolones
Authors: Cativiela Carlos , Sánchez‐Ferrando Francisco
Published: May 2005

The technique previously described as two‐bond heteronuclear selective NOE difference was improved to yield quantitative data on NOE enhancement factors by recording separately the unperturbed and the perturbed FIDs. In this way the E and Z stereoisomers of 4(α‐arylethylidene)‐2‐phenyl‐5(4H)‐oxazolones were easily distinguished. The latter showed positive NOE ehancements on quaternary carbons placed two, three and four bonds away from the irradiated methyl protons, as well as a negative NOE on a nearby protonated carbon.
Computer‐assisted analysis of the 1H NMR spectra of peracetylated galactose‐containing oligosaccharides
Authors: Jimeno M. Luisa , Martin‐Lomas Manuel , Alemany Antonio
Published: May 2005

The computer‐assisted analysis data of t1H NMR spectra of peracetylated α‐and β‐1 →3‐ and ‐1 → 4‐linked D‐gal‐actopyranosyl‐D‐galactopyranoses and several tetraacetylatedO‐methyl derivatives of D‐galactopyranose are reported.
NMR investigations on benzheteroazoles. 2—NMR investigations of N‐acylated 2‐aminobenzimidazoles
Authors: Gründemann E. , Graubaum H. , Martin D. , Schiewald E.
Published: May 2005

The 13C NMR chemical shifts of 74 N‐acylated 2‐aminobenzimidazoles were determined and assigned. The chemical shifts are discussed as a function of electronic and spatial substituent effects. Line broadening for certain C signals are traced to prototropy at N‐1 and N‐3, and N‐3 and Nexo.
Relaxation studies of carbonyl rhenium clusters. Part 2—relaxation mechanisms and estimation of the 13C chemical shielding anisotropy in the [Re3(μ‐H)4(CO)10]− anion at low temperature
Authors: Beringhelli Tiziana , D'Alfonso Giuseppe , Molinari Henriette
Published: May 2005

Application of the non‐selective inversion recovery technique to 13C spectra of moderately enriched [Re3(μ‐H)4(CO)10]− indicates that relaxation times, at low temperatures, are strongly field dependent and decrease with increasing field strength. Measurements performed at 183 K and at 20.15, 50.31 and 67.88 MHz indicate that chemical shielding anisotropy is dominant at higher fields, which differs from the behaviour previously observed at room temperature where the main relaxation pathway is scalar coupling with the quadrupolar rhenium isotopes. The 13C chemical shielding anisotropy was estimated to be in the range 476±40 ppm. Interactions with quadrupolar rhenium also affect the hydrogen spin‐spin relaxation times.
NMR spectra and stereochemistry of 2‐(piperidin‐2‐ylmethyl)cycloalkanols
Authors: Begley Michael J. , Crabb Trevor A. , Roch Olive G.
Published: May 2005

2‐(Piperidin‐2‐ylmethyl)cycloalkanols have been synthesized by the reaction between 2‐picolyllithium and cycloalkene oxides, followed by catalytic hydrogenation of the resulting 2‐(pyridin‐2‐ylmethyl)cycloalkanols. The configurations of the 2‐(piperidin‐2‐yl‐methyl)cycloalkanols were assigned by comparing their 13C and 1H NMR parameters with those of 2‐(piperidin‐2‐ylmethyl)cyclohexanols of known (x‐ray) configuration.
The study of sipholanes by two‐dimensional NMR spectroscopy
Authors: Carmely S. , Kashman Y.
Published: May 2005

The complete assignment of the 13C and 1H NMR spectra of sipholenol‐A and sipholenone‐A, two new triterpenes isolated from a marine sponge, were achieved from 1H‐13C shift correlation diagrams.
Swinholide‐A, a new marine macrolide. Complete assignment of 1H and 13C spectra by 2D NMR techniques
Authors: Carmely Shmuel , Rotem Michal , Kashman Yoel
Published: May 2005

1H and 13C NMR spectra of the novel marine macrolide swinholide‐A, which provide the basis for its structure elucidation, have been completely assigned by parallel use of 1D and homo‐ and hetero‐nuclear 2D NMR techniques. Swinholide‐A (1) probably a polyketide, is a 22‐membered macrolide embodying a dihydropyran ring and a 10‐carbon side‐chain ending with a substituted tetrahydropyran ring. The high degree of overlap of eleven CH—O and nine CH2 signals in the 1D proton NMR spectrum of 1 necessitated the structure elucidation of swinholide‐A tetraformate (2) by 2D homo‐ (up to 6J with formyl groups) and hetero‐nuclear NMR correlations. Formyl groups can be good structural probes in complex polyalcohols, as shown by the observed 5J and 6J formate couplings in 2.
13C NMR spectra of some o‐carbonyl derivatives of naphthols
Authors: Rażniewska‐Lazȩcka G. , Da̧mbska A. , Janowski A.
Published: May 2005

All the signals in the 13C NMR spectra of o‐carbonyl naphthol derivatives (i.e. o‐hydroxy aldehydes, o‐hydroxy methyl ketones and methyl esters of o‐hydroxy acids) are assigned on the basis of the additivity rule of substituent‐induced shifts and selective 13C{1H} hetero‐decoupling experiments [sometimes in the presence of Yb(fod)3]. The differences between the experimental chemical shifts and the values calculated on the basis of the additivity of substituent‐induced shifts are also given; these may be regarded as ‘intramolecular hydrogen bond‐induced shifts’.
15N and 13C NMR spectroscopy of 1,2,6‐thiadiazine 1,1‐dioxide derivatives and fused systems
Authors: Goya Pilar , Ochoa Carmen , Rozas Isabel , Alemany Antonio , Jimeno M. Luisa
Published: May 2005

The natural abundance 15N NMR spectra of sulphamide, sixteen 1,2,6‐thiadiazine and two 1,2,4,6‐thiatriazine derivatives, phenylbutazone and antipyrine have been recorded for the first time. The influence of substituents on nitrogen chemical shifts and the effect of intercalation of SO2 and CO groups between two nitrogen atoms are discussed. Prototropic tautomerism was also studied. 13C NMR data for some of the 1,2,6‐thiadiazine and thiatriazine derivatives are reported.
1H and 13C NMR studies of substituted nitropyridines and nitrobenzenes
Authors: Nudelman N. S. , Cerdeira S. B.
Published: May 2005

The 1H and 13C NMR spectra of 3‐nitro‐, 5‐nitro‐ and 3,5‐dinitro‐2‐methoxypyridines have been determined. The results show the preferred cis conformation for the 2‐methoxy group, and the importance of steric repulsion between the oxygen atom of this group and those of the o‐nitro group which hinders conjugation in the 3‐nitro‐substituted derivatives. Similar steric inhibition of resonance is observable with 2‐N‐butylamine‐, 2‐N‐cyclohexylamine‐ and 2‐(N‐piperidyl)‐substituted nitropyridines, whose 1H and 13C NMR spectra were also determined. In the case of the secondary amines, a hydrogen bond between the amino proton and the 3‐nitro group was clearly detected. 1H and 13C NMR spectra of 2,6‐dinitro‐, 2,4‐dinitro‐ and 2,4,6‐trinitro‐2‐R‐benzenes (R = OCH3, NHC4H9, NH‐cyclo‐C6H11, NC5H10) were also recorded and compared with those of the pyridine derivatives. The electronic aza and nitro group effects are comparable if conjugation of the nitro group is not hindered.
Multinuclear NMR and infrared spectroscopic study of a series of cis‐Mo(CO)4(py‐R)2 (Py‐R = 3‐ or 4‐substituted pyridine) complexes: Relationship between chemical shifts and infrared force constants and the Taft electron donor/acceptor parameters of the pyridine substituents
Authors: Box James W. , Gray Gary M.
Published: May 2005

Poor correlations are normally observed between the chemical shifts of the various NMR‐active nuclei in Mo carbonyl complexes of group 15 ligands as the group 15 atom substituents are varied. It is possible to observe good chemical shift correlations and to develop relationships between chemical shift and changes in electron density due to variations in the group 15 atom substituents, provided that this variation does not change the cone angles of these ligands. This is the case for complexes of the type cis‐Mo(CO)4(py‐R)2 (py‐R = 3‐ or 4‐substituted pyridine). Good to excellent linear correlations are observed between the chemical shifts of the cis and trans CO 13C and 17O resonances and the 95Mo resonances in these complexes, and between these chemical shifts and the CO infrared stretching force constants of the complexes. Good to excellent correlations also occur between either the chemical shifts or the CO infrared stretching force constants and either the Taft σm/σp or σR and σ1 parameters. These correlations provide significant insights into the relationship between the electron donor/acceptor abilities of the pyridine ligands and the NMR and infrared spectra exhibited by the cis‐Mo(CO)4(py‐R)2 complexes.
Identification of guayule triterpenes by two‐dimensional and multipulse NMR techniques
Authors: Komoroski Richard A. , Gregg Earl C. , Shockcor John P. , Geckle J. Michael
Published: May 2005

Five triterpene natural products have been isolated from the resin of the guayule bush (Parthenium argentatum) and four of these identified using two‐dimensional (2D) and multipulse NMR techniques. Of the five structures, two have been reported previously. Two of the structures contain an uncommon seven‐membered ring incorporating an ether linkage. The 2D carbon–carbon chemical shift correlation (2D INADEQUATE) and DEPT multiplicity experiments are used as the primary techniques for determining the molecular skeleton. Supporting evidence is provided by the carbon–proton and proton–proton (COSY) chemical shift correlation experiments, and by preparation of simple derivatives. The merits and problems of the various techniques are discussed. We reverse the previous assignments of C‐27 and C‐29 of cycloartanone.
Use of lanthanide shift reagents to probe the conformation of fatty acids in solution by 13C NMR
Authors: Pons Miquel , Chapman Dennis
Published: May 2005

The conformational analysis of short polymer chains involves the use of statistical models, and their predictions must be checked against experimental information. Ytterbium‐induced shifts in the 13C NMR spectra of fatty acids provide a non‐perturbing, straightforward method of simultaneously obtaining positional information about all the carbon atoms up to nine bonds away from the comuplexation point. Experimental results for saturated and unsaturated C‐18 fatty acids are compared with the predictions of a restricted isomeric states (RIS) model.
Stereochemical investigations on (E)‐homoeburnane derivatives by 1H and 13C NMR spectroscopy
Authors: Tóth Gábor , Szántay Csaba , Kardos Zsuzsa , Incze Mária , Sóti Ferenc , Szántay Csaba , Kotovych George
Published: May 2005

Several 14‐hydroxy‐14a‐methyl‐(E)‐homoeburnane diastereoisomers have been synthesized and studied by 1H and 13C NMR spectroscopy. ID NOE difference experiments, together with proton‐proton correlation and decoupling measurements, have allowed the complete assignment of the 1H and 13C NMR spectra. The relative configurations and predominant conformations have been established.
Dinuclear tungsten and molybdenum complexes with fulvalene ligands: Assignment of their 1H and 13C NMR spectra by one‐dimensional heteronuclear noe difference spectroscopy
Authors: Meyerhoff Dieter J. , Nunlist Rudi , Tilset Mats , Vollhardt K. Peter C.
Published: May 2005

One‐dimensional heteronuclear NOE difference spectroscopy was used to assign 1H and 13C NMR spectra of dinuclear fulvalene complexes with tungsten and molybdenum. It was found that metal‐metal bonded complexes show 1H chemical shifts which are the inverse of those in non‐metal—metal bonded complexes, whereas the relative 13C chemical shifts are not affected by the metal—metal bond.
A caveat concerning ‘ultra‐high‐resolution nmr.’ effects of magnetic field induced alignment
Authors: Bastiaan E. W. , Bulthuis J. , MacLean C.
Published: May 2005

Line positions in high‐resolution NMR spectra may be affected by dipolar couplings and anisotropic shift contributions, which arise from the partial orientation of the molecules by the magnetic field of the spectrometer. It is shown that, depending on the system studied, these effects can be larger than 0.01 Hz at moderate fields (ca 7 × 104 G), and should therefore be considered when claiming accuracies of 10mHz or better.
Carbon‐13 NMR spectra of nineteen (1R)‐(+)‐camphor derivatives
Authors: Crull George B. , Garber Albert R. , Kennington John W. , Prosser Christina M. , Stone Phillip W. , Fant James W. , Dawson John H.
Published: May 2005

Nineteen derivatives of (1R)‐( + )‐camphor with deutero, fluoro, bromo, iodo, keto, and hydroxyl functionalities at carbons 3, 5, 8, or 9 have been examined using 13C NMR. The chemical shifts for each carbon of these substituted camphor derivatives have been assigned using broad band decoupling and the refocused INEPT pulse sequence.
Heterocyclic β‐enamino esters 43—easy 13C NMR distinction between aryl‐substituted dimroth isomers of the 1,2,3‐triazole series
Authors: Wamhoff H. , Bohlen J. , Yang S. Y.
Published: May 2005

5‐Amino‐1‐aryl‐1,2,3‐triazoles and 5‐anilino‐1,2,3‐triazoles can be easily distinguished by their 13C NMR spectra. Thus, C‐4 and C‐5 of some studied 5‐anilino isomers are deshielded by 2–5 ppm in comparison with the corresponding 5‐amino‐1‐aryl isomers. From the 13C NMR signals of the aryl carbons in the same 5‐anilino isomers, C‐6 is shifted downfield (ca 9 ppm; –I effect), whereas C‐7 and C‐9 are shifted upfield (ca 7 and 10 ppm, respectively; +M effect). This allows a fast and easy assignment of both Dimroth isomers.
13C NMR spectroscopy of naphtho‐γ‐pyrones
Authors: Priestap Horacio A.
Published: May 2005

The 13C NMR spectra of three naphtho‐γ‐pyrones produced by Aspergillus fonsecaeus (NRRL 67, 0 16–1), viz. 5‐hydroxy‐6,8‐dimethoxy‐2‐methyl‐4H‐naphtho[2,3‐b]pyran‐4‐one (rubrofusarin B), 2,3‐dihydro‐2,5‐dihydroxy‐6,8‐dimethoxy‐2‐mehtyl‐4H‐naphtho[2,3‐b]pyran‐4‐one (fonsecin B) and 2,3‐dihydro‐2,5,8‐trihydroxy‐6‐methoxy‐2methyl‐4H‐naptho[2,3‐b]pyran‐4‐one (fonsecin), have been determined. Assignments of the carbon resonances were carried out from chemical shifts, long‐range carbon‐hydrogen couplings and hydrogen–deuterium exchange information. Carbon shift assignments previously reported for fonsecin have been revised. The C‐4 and C‐5 signals show that the angle of twist of the carbonyl group with the aryl ring system is larger in fonsecin than in fonsecin B, indicating the occurrence of different preferred conformations in the dihydropyrone ring of these compounds.
Selenium‐77 NMR spectral analysis of selected substituted selenanes, selenanones and 3‐selena‐7‐azabicyclo[3.3.1]nonanes and derivatives
Authors: Thompson M. Daniel , Smith Gary S. , Ramalingam K. , Berlin K. Darrell
Published: May 2005

A series of selenanes and selenanones have been examined using 77Se NMR analysis. Sharp resonances were found in all cases whether recorded at 47.7, 51.4 or 57.22 MHz or in DCCI3 or DMSO‐d6. Diphenyl diselenide was used as the external reference, but all resonances were subsequently referred to dimethyl selenide (0°C, O ppm). It was observed that in the selenanone family any substituent at the α‐, β‐ or γ‐positions exerted a significant effect on the 77Se resonances. The same was true in the selenanes. Moreover, the presence of a chair‐chair or chair‐boat form in certain 3‐selena‐7‐azabicyclo[3.3.1]nonan‐9‐ones and related 3‐selena‐7‐azabicyclo[3.3.1]nonanes (and hydroperchlorates) induced remarkable differences in 77Se shifts. Some general observations and conclusions are delineated in terms of the influence of various groups on the 77Se resonances in these cyclic systems.
NMR spectra of betaines from marine algae
Authors: Blunden Gerald , Gordon Sally M. , Crabb Trevor A. , Roch Olive G. , Rowan Michael G. , Wood Brian
Published: May 2005

The 1H and 13C NMR spectroscopic characteristics of a range of behines, most of which are found in marine algae, are described. The spectral features are an important aid to the identification of these compounds. In the 13C NMR spectra, some (14N, 13C) couplings are clearly observed. The FAB mass spectral characteristics of some of these compounds are also described.
Carbon‐13 NMR of solid phenylazo‐2‐naphthols: Tautomerism and (13C, 14N) residual dipolar coupling
Authors: Harris Robin K. , Jonsen Paul , Packer Kenneth J. , Campbell Colin D.
Published: May 2005

The use of 13C CP/MAS NMR is illustrated by the determination of the tautomeric structures of some phenylazo‐2‐naphthols in the solid state. The effects of (13C, 14N) residual dipolar coupling for such systems are discussed.
17O NMR spectroscopy: Referencing in diamagnetic and paramagnetic solutions
Authors: Gerothanassis Ioannis P. , Lauterwein Jürgen
Published: May 2005

Several referencing techniques for measuring 17O NMR chemical shifts in diamagnetic and paramagnetic solutions have been examined. 1,4‐Dioxane is recommended as an external reference standard for diamagnetic solutions because the 17O resonance position is independent of temperature between 27 and 90°C. At 40°C the 17O chemical shift, within experimental error, corresponds to that of doubly distilled water. Nitromethane cannot be considered as a suitable internal reference because of large solvent effects on the 17O chemical shift. Further, in organic solutions its lanthanide‐induced chemical shifts are not negligible. For the study of paramagnetic solutions the combined use of a cylindrical and a spherical cell is proposed: the 17O resonance of either the magnetically active solvent or a convenient compound added to the solution is recorded in both cells; the chemical shift difference between the two measurements is the bulk magnetic susceptibility shift.
Deuterium isotope effects in propylene and ethylene ozonide
Authors: Choe Jong‐In , Choi Hyung‐Soo , Kuczkowski Robert L.
Published: May 2005

The proton NMR spectra of four deuteriated species of propylene ozonide and five of ethylene ozonide were analysed. The deuterium isotope shifts were 0.0140 ppm (H gem to D), 0.0034 ppm (H trans to D) and 0.0015 ppm (H cis to D) for propylene ozonide. The same trends were observed in ethylene ozonide. The isotope shifts were not additive when two geminal protons were substituted by deuterium. The relative intensities of microwave rotational and proton NMR transitions were compared for propylen ozonide‐d1 prepared stereoselectively in order to assign unambiguously its chemical shifts and spin–spin splittings.
Interactions between protonated retinal schiff base and various counter ions: A study by two‐dimensional NOE NMR spectroscopy
Authors: Ghirlando Rodolfo , Berman Elisha , Baasov Timor , Sheves Mordechai
Published: May 2005

Using two‐dimensional NMR spectroscopy, the spatial location of various carboxylate anions relative to the polyene chain of the protonated Schiff base of all‐trans‐retinal was determined. The observed intermolecular NOE cross‐peaks between a proton on the counter ion and a proton near the nitrogen atom indicate the existence of ion‐pair formation between the protonated retinal Schiff base and various counter ions in chloroform. The results suggest that the most likely site of the carboxylate group of the counter ion is in the immediate vicinity of the positively charged nitrogen atom of the retinal Schiff base.
Assignment of carbon‐13 nuclear magnetic resonance spectra of some friedelanes
Authors: Patra Amarendra , Chaudhuri Swapan Kumar
Published: May 2005

Carbon‐13 resonance assignments of cerin acetate, 2α‐pyridine‐N‐oxyfriedelan‐3‐one, epi‐cerin and its acetate, 3α‐hydroxyfriedelan‐2‐one and its acetate, 3‐hydroxyfriedel‐3‐en‐2‐one and its acetate, friedelane‐3,7‐dione, 3β‐hydroxyfriedelan‐7‐one, canophyllol, friedelolactone and friedelolactone‐2α‐yl acetate, friedelane‐2α,3β‐diol and its diacetate, friedelane‐2β,3α‐diyl diacetate, pachysandiyl‐A diacetate and friedelane‐2β‐3β‐diyl diacetate have been made. The carbon signals of 3‐oxofriedelan‐29‐ol and its acetate, methyl 3‐oxofriedelan‐29‐oate, 3‐oxofriedelan‐30‐ol, maytenfoliol, maytensifolin‐A, maytensifolin‐B, pachysonol and pristimerin reported in the literature have also been considered for their specific resonance assignments. A few signal assignments of some friedelanes, viz. friedelan‐28‐ol, friedelan‐29‐ol, friedelan‐30‐ol, friedelan‐29‐al, 3‐oxofriedelane‐21α,26‐diol and zeylasterone, reported recently by others, are unusual and have been reviewed.
1H NMR chemical shifts of gaseous amines
Authors: Chauvel J. Paul , Folkendt Michael M. , True Nancy S.
Published: May 2005

Gas‐phase 200 MHz 1H NMR spectra of nineteen primary and nine secondary aliphatic amines were obtained at total densities below 0.15 amagat at 148.6 °C. Theoretical predictions of 1H chemical shifts of ammonia and methylamine are compared with the gas‐phase experimental values. The amino proton chemical shifts move downfield with increasing alkyl group size. For series of amines with similar structural geometry about the amino nitrogen, the 1H amino proton chemical shifts correlate reasonably well with gas‐phase basicities as measured via ion cyclotron resonance spectroscopy (r = 0.95 for a linear fit of chemical shift to the gas‐phase basicity for the primary amines and r = 0.93 for the secondary amines). Gas‐phase 1H NMR spectra for linear diamines, hydroxyamines, cyclic amines and substituted anilines were also obtained.
Carbon‐13 NMR Studies. 127—13C and 2H NMR investigations of 1H/2H exchange in isomeric tricyclic [5.2.1.0] and [5.3.1.0] ketones
Authors: Jurlina Jeffrey L. , Patel Hemant A. , Peiris Sriyawathie , Stothers J. B.
Published: May 2005

Under strongly basic conditions (t‐BuO−/t‐BuOD at 185 °C), the 9,9‐dimethyltricyclo[5.2.1.02,6]‐ and ‐[5.2.1.01,5]decan. 8‐ones and the homologous [5.3.1.0]undecanones undergo multi‐site 1H/2H exchange. The total 2H uptake was monitored by mass spectrometry, while the individual sites of exchange were established by 13C NMR spectroscopy. The relative rates and stereoselectivity of incorporation at each site were determined by 2H NMR. These results extend our knowledge on the activating effect of the carbonyl group for proton abstraction at remote centres and are compared with earlier data for several related bi‐ and tricyclic systems. In addition, the 13C spectra provide several examples of geminal and vicinal 2H‐induced isotope shifts in tricyclic carbon skeletons.