bluuebunny/crossref_metadata_2025 huggingface dataset:
Das Diffusionsschweißen von Titanlegierungen
Authors: Kellerer Helmut
Published: May 2005

Beim Diffusionsschweißen laufen teils nacheinander, teils gleich‐zeitig vier Prozesse ab: Oberflächenverformung, atomare Bindung, Grenzflächendiffusion und Kornwachstum.– Es wird untersucht, wie diese einzelnen Vorgänge jeweils von den technologischen Verfahrens–und Materialparametern abhängen, wobei teilweise eine mathematische Erfassung möglich ist. Für die technische Durchführung der Diffusionsschweißung stehen mehrere Verfahren zur Verfügung, deren Vorteile und Nachteile diskutiert werden. – Die bisherigen Erfahrungen mit dem Diffusions‐schweißen von Titanlegierungen haben gezeigt, daß in der Schweißnaht Grundmaterialfestigkeit erreicht werden kann, bei manchen Bauteilen ergeben sich sogar Festigkeitsgewinne. Typische Fehlerquellen beim Diffusionsschweißen von Titan werden aufgezeigt. Abschließend wird anhand von Beispielen auf die Einsatzgebiete eingegangen, wo das Diffusionsschweißen wirtschaftliche und konstruktive Vorteile erbringen kann.
Eine einfache Methode zum Nachweis löslicher dimethylsilikonhaltiger Verarbeitungshilfsmittel
Authors: Kurz R. , Schmid K. H.
Published: May 2005

Zum schnellen Nachweis löslicher Dimethylsilikonverbindungen, die auf Oberflächen von Bauteilen z. B. als Reste von Verarbeitungshilfsmitteln oder als Bestandteile von Lacken in bestimmten Fällen Ursache unerwünschter Effekte sein können, hat sich ein sog. „TRI‐Schütteltest”︁ bewährt. Silikonverbindungen setzen die Oberflächenspannung von Trichloräthylen (TRI) herab, so daß beim Schütteln Schaum entsteht. Die Beständigkeit des Schaumes ist ein Maß für den Silikongehalt der Lösung zwischen 10 μg Silikon/ml TRI (Nachweisgrenze) und etwa 100 mg/ml TRI (Sättigung).
Walzplattierte Grobbleche für den Apparatebau
Authors: Müsgen B.
Published: May 2005

Bedeutung plattierter Grobbleche im Apparatebau für die chemische und petrochemische Industrie. Beschreibung des Verfahrens, mit dem ferritische Stähle und korrosions‐ bzw. hitzebeständige Werkstoffe sich durch Walzplattieren dauerhaft verbinden lassen. Hinweise auf lieferbare Werkstoffkombinationen und Abmessungen sowie auf notwendige Qualitätsanforderungen.

Ergebnisse von Untersuchungen der Verbindungsschicht. Verteilung der Elemente zwischen Auflage‐ und Grundwerkstoff. Haftfestigkeit, Korrosionsverhalten, Zähigkeits‐ und Festigkeitseigenschaften des Schichtsystems, Wärmebehandlung, Schneiden und Schweißen plattierter Grobbleche. Anwendungsbeispiele.
Oberflächenspezifische Analysenverfahren (AES/SAM, ESCA/XPS, SIMS) und ihr Einsatz zur Untersuchung von Verschleiß‐Schutzschichten
Authors: Hantsche H. , Habig K.‐H.
Published: May 2005

Es werden die analytischen Möglichkeiten aufgezeigt, die sich ergeben, wenn man mehrere oberflächenspezifische Analysenverfahren, hier speziell AES/SAM, ESCA(XPS) und SIMS, zur Charakterisierung von Werkstoffoberflächen kombiniert einsetzen kann.

Die Grundprinzipien werden besprochen, die Vor‐ und Nachteile der Methoden miteinander verglichen – insbesondere in bezug auf die klassische Röntgen‐Mikroanalyse – und schließlich anhand von Beispielen aus dem tribologischen Bereich erläutert.
The effect of Graphitization on the Mechanical Properties of twodimensional carbon – carbon composites
Authors: Sedghi A. , Fard F. Golestani
Published: May 2005

In this article the effect of graphitization in twodimensional c‐c composite bodies prepared by impregnation of novalak resin is reported. Mechanical properties were determined by bending tests and microstructural features were studied by SEM and XRD. It was found that primary graphitization at 2300°C followed by graphitization at 2500°C improves the mechanical strength remarkably. Repeated graphitization and long – term treatment at 2500°C, however, found to have an adverse effect. Microstructural observations revealed that the level of strength is mainly controlled by a sheath developed around the fibre during graphitization.

Applying an improper thermal regime affects the matrix – fibre adherence and may cause the destruction of the fibres. This enhances the crack propagation and causes early failure of composite body under loading.
Chromatographic evaluation of chiral (1R‐trans)‐N, N′ ‐1,2‐cyclohexylenebisbenzamide‐oligodimethylsiloxane copolymeric stationary phases for capillary supercritical fluid chromatography
Authors: Petersson Patrik , Markides Karin E. , Johnson Deborah F. , Rossiter Bryant E. , Bradshaw Jerald S. , Lee Milton L.
Published: May 2005

A novel approach to the design of chiral stationary phases (CSPs) is illustrated by the synthesis and evaluation of selective and efficient copolymeric CSPs with alternating chiral (1R‐trans)‐N, N′‐1,2‐cyclohexylenebisbenzamide and achiral (oligodimethylsiloxane) blocks. These materials are shown to resolve a variety of chiral diols. Evaluation of the performance of one of these phases in GC and SFC suggests that SFC can produce higher resolution because of its lower operating temperature which facilitates solute‐stationary phase interactions. The influence of different chiral (position of substitution) and achiral (chain length) blocks of the copolymer on solute retention, efficiency, chiral selectivity, and resolution were studied, as well as the reproducibility of the column preparation method.
Molecular formula determination of halogenated compounds in environmental samples using gas chromatography and atomic emission dection
Authors: Pedersen‐Bjergaard Stig , Asp Tone Normann , Vedde John , Greibrokk Tyge
Published: May 2005

Atomic emission spectroscopy coupled with capillary gas chromatography (GC) has been evaluated for molecular formula determination of several chlorinated and brominated compounds present in three environmental samples. Variations in elemental responses due to compound type, poor chromatographic resolution, and small signals relative to the background were all found to complicate molecular formula calculations. About 20% of the calculated molecular formulas presented in this paper agreed with theoretical values. For most applications, identifications based solely on GC coupled with theoretical values. For most applications, identifications based solely on GC coupled with atomic emission detection (AED) are not sufficiently accurate. However, the combination of elemental information derived form a GC‐AED analysis with complementary data obtained from other detection techniques results in a strong analytical tool for analyte identification.
Nitrogen‐15 NMR characterization of 7‐methylguanosine and its base‐pair with cytidine in dimethyl sulphoxide
Authors: Barbarella G. , Bertoluzza A. , Tugnoli V.
Published: May 2005

The neutral and the protonated, positively charged, forms of 7‐methylguanosine have been characterized by 15N NMR in dimethyl sulphoxide. It is shown that in this solvent protonated 7‐methylguanosine gives specific interactions with cytidine at the same sites as those involved in the guanosine‐cytidine Watson‐Crick base‐pairs present in nucleic acids.
NMR studies of indoles and their N‐carboalkoxy derivatives
Authors: Morales‐Ríos M. S. , Joseph‐Nathan P.
Published: May 2005

The 13C NMR assignment of indoles and 5‐methoxyindoles substituted at position 3, and some of their N‐carboalkoxy derivatives, was achieved from one‐ and two‐dimensional NMR experiments. Substituent chemical shifts and 1 J(CH) values were evaluated. The dynamic processes of N‐carboalkoxyindoles and N‐carboalkoxyindoline observed by high‐field 1H NMR show the existence of two preferred rotamers around the carbamate NC(O)OR bond, which was interpreted in terms of frequency/field strength‐dependent phenomena.
Cycloaddition reactions of cephalosporin compounds. IX—1H and 13C NMR stereochemical study of the 1,3‐dipolar cycloadditions of diazoalkanes to 2‐methylenecephem derivatives
Authors: Cs. Jászberény J. , Pitlik J. , Batta Gy. , Kövér K. E. , Kollár K.
Published: May 2005

A series of known and novel 2‐methylenecephem derivatives were prepared and their reactions with diazomethane, phenyldiazomethane and diphenyldiazomethane were studied. The initially formed 1‐pyrazolino derivatives easily underwent spontaneous loss of nitrogen, leading to 2‐spirocyclopropylcephems. The two reaction products, formed in a 3:1 to 8:1 ratio on addition of diphenyldiazomethane, were separated by column chromatography and distinguished by their 1H and 13C NMR spectra. The 1H NMR spectra did not exclude the possibility of 1‐pyrazoline formation, but elemental analysis and 13C data corroborated the previous assumption that loss of nitrogen took place, even in those cases when it did not occur during the reaction.
Dynamic NMR study of the electronic state of heteroaromatics. III—Pyrylium salts or intramolecularly bridged pentamethine cyanines?
Authors: Kleinpeter E. , Spitzner R. , Schroth W. , Pihlaja K. , Mattinen J.
Published: May 2005

The 13C NMR spectra and the temperature‐dependent 1H NMR spectra of a series of NR2‐substituted pyridines and pyrones were studied, and the 13C chemical shifts and the rotational barriers about the exocyclic partial C,N double bonds were compared with the corresponding values for suitable pyridinium, pyrylium and thiopyrylium salts. The NMR spectroscopic results are discussed in the light of the electronic state and mesomerism in the species studied; the salts in question should be named, from the electronic point of view, more realistically as bridged pentamethine cyanines rather than pyridinium, pyrylium and thiopyrylium salts.
Conformations in solution of four 2,4,5,7‐tetramethyloctane‐4,5‐dicarboxylates: Molecular mechanics and NMR studies
Authors: Holland Kelvyn A. , Rae Ian D. , Weigold Josephine A.
Published: May 2005

Potential energy calculations (MM2), low‐temperature 1H and 13C NMR spectra and 1H–1H COSY spectra are reported for four octane derivatives, the central portions of which constitute tetrasubstituted succinates. The existence of several conformers differing in stereochemistry in this central moiety is predicted by calculations and observed in low‐temperature NMR. The periphery of each molecule is in an extended configuration, as shown by the existence of long‐range (W‐plan) couplings involving the methyl groups.
Aza crown ethers. 13C and 1H NMR studies of ring conformations and stereochemically dependent shifts in N‐substituted dibenzodiaza‐18‐crown‐6 ethers and a nine‐membered analog
Authors: Buchanan G. W. , Landry D. J.
Published: May 2005

Remarkably large (> 10 ppm) 13C NMR chemical shift differences are observed in solution and in the solid phase between ortho aromatic carbons of structurally analogous dibenzodiaza‐18‐crown‐6 ethers and their 9‐membered ring counterparts. On the basis of geometries deduced from 1H1H NOESY results, the upfield 13C chemical shifts in the 18‐membered systems are attributed to cis coplanar interactions between the terminal carbons of these torsional networks. Overall mobilities of 9‐ and 18‐membered ring systems are examined via 13C spin–lattice relaxation times.
γgaucheEffects in the 1H and 13C NMR spectra of steroids. II
Authors: Hammann P. E. , Kluge H. , Habermehl G. G.
Published: May 2005

γgaucheEffects of 17β‐ and 7α‐substituted 14α‐steroids were studied by 1H and 13C NMR spectroscopy. A linear correlation was found between the 1H chemical shift of H‐12β and the 13C chemical shift of C‐12 for C‐17β‐substituted steroids and between the chemical shifts of H‐14α and C‐14 in C‐7α‐substituted compounds.
An NMR study of the hydroxylamine‐induced denitration of nitrocellulose, nitroamylose and some model monosaccharide nitrate esters
Authors: Bulusu S. , Axenrod T. , Liang B. , Yuan L.
Published: May 2005

The previously known method of partial denitration of trinitrocellulose by hydroxylamine in pyridine was further investigated by NMR and applied to trinitroamylose and several other monosaccharide nitrates to study its selectivity. The sites of denitration were determined in each case using 13C and 15N NMR and, in most cases, by 2D homo‐ and hetero‐nuclear (15NOC1H and 13C1H) chemical shift correlations. The results indicate that denitration of the polysaccharide nitrates is a highly regiospecific reaction occurring at the 2‐position only, whereas with the monosaccharide nitrates denitration takes place with less selectivity, at the 4‐position predominantly, and to a lesser extent at the 3‐position.
13C NMR spectra of multifunctional bile acid derivatives
Authors: Blossey Erich C. , Ford Warren T. , Periyasamy Mookkan
Published: May 2005

Carbon‐13 NMR signals were assigned to a set of methyl 5β‐cholanoates having multiple functional groups, including hydroxy, carbonyl and acetoxy groups. Assignments were based on empirical chemical shift rules for α‐, β‐ and γ‐substituent effects, direct spectral comparison with compounds of similar structure, DEPT and 2D‐HETCOR. Use of β‐substituent effects permitted the assignment of structural changes at positions 3, 7 and 12 of the steroidal nucleus.
Carbon‐13 chemical shift anisotropies of solid amino acids
Authors: Ye Chaohui , Fu Riqiang , Hu Jianzhi , Hou Lei , Ding Shangwu
Published: May 2005

An approach to spinning sideband (SSB) separation of protonated and non‐protonated carbons in slow spinning conditions via dipolar dephasing is proposed. This method offers two features: SSB spectral simplification, which greatly reduces the overlaps encountered in a usual SSB spectrum, and spectral distinction of overlapped resonances for protonated and non‐protonated carbons. The 13C chemical shift anisotropies of the 20 amino acids as polycrystalline powdered solids were completely measured with the SSB intensity analyses as an application of the suggested approach.
Application of Hahn‐echo extended pulse sequences to phosphorus–nitrogen compounds. Determination of coupling signs and detection of 15N31P15N isotopomers in natural abundance
Authors: Wrackmeyer Bernd , Köhler Christian , Kupče Eriks
Published: May 2005

Hahn‐echo extended (HEED) pulse sequences in one‐ and two‐dimensional experiments were successfully applied to phosphorus–nitrogen compounds with two PN bonds {2‐chloro‐1,3‐dimethyl‐1,3,2‐diazaphospholidine (1), 2‐tert‐butyl‐1,3‐dimethyl‐1,3,2‐dizaphospholidine (2), bis(diethylamino)chlorophosphane (3) and bis(diethylamino)phosphenium cation (4; counterion [AlCl4]−)}. In the case of 2, the 31P resonance signal was detected as a sharp triplet for the 15N31P15N isotopomer in natural abundance: the secondary isotope effect on the coupling constant 1J(31P15N) in 14N31P15N and 15N31P15N isotopomers is < 0.05 Hz; the isotope‐induced shifts 1Δ 15/14N(31P) are additive. The value of 1Δ 15/14N(31P) in the phosphenium cation 4 is markedly more negative than that in its precursor 3 or other aminophosphanes. For 2, the absolute signs of the coupling constants 2J(15N 1H) ( < 0), all 3J(31P1H) ( > 0), 1J(31PC13C) ( < 0), 2J(31PC13C) ( > 0), 2J(31PN 13CCH3) ( > 0) and 2J(31PNCCH2) ( < 0) were determined using 1H detected 2D inverse pseudo triple resonance 1H{(13C)31P} experiments and 2D 13C1H, 15N1H and 31P1H heteronuclear shift correlations.
NMR assignments for 6‐hydroxy‐2‐methyl‐2‐(4‐methylpent‐3‐enyl)‐2H‐1‐benzopyran (cordiachromen A)
Authors: Kim In Kyu , Park Sun Ku , Erickson Karen L.
Published: May 2005

6‐Hydroxy‐2‐methyl‐2‐(4‐methylpent‐3‐enyl)‐2H‐1‐benzopyran, a fairly common naturally occurring terpene hydroquinone, was isolated from the Korean ascidian Aplidium multiplicatium and its 1H and 13C NMR assignments were made and/or corrected from earlier literature values.
Dérivés Alléniques du Phosphore. Influence de l'État de Coordination du Phosphore et de la Nature des Radicaux Liés au Phosphore sur les Signes de J(PH)
Authors: Simonnin Marie‐Paule , Charrier Claude , Lecourt Marie‐José
Published: May 2005

Les signes des constantes de couplage phosphore‐proton dans les dérivés alléniques du phosphore ont été déterminés soit par analyse des spectres de type AB2X, soit par Double Résonance, et les signes absolus probables ont été obtenus en supposant que 3J(PH) est toujours positif.

Dans les oxydes de phosphines alléniques, les signes sont les suivants: 2J(PH) +, 3J(PH) +, 4J(PH) −, 5J(PH) + et 4J(PH) dépend principalement des effets inducteurs des radicaux liés au phosphore.

Dans les phosphines alléniques, les signes sont: 2J(PH) +, 3J(PH) +, 4J(PH) − et + et 4J(PH) dépend à la fois des effets inducteurs et de résonance des radicaux liés au phosphore: ce couplage, normalement négatif, deviant positif lorsque le phosphore porte des substituants donneurs par effet de résonance.

Ces résultats sont interprétés par l'existence d'une liaison pπdπ dans les phosphines.
The NMR spectra and conformations of cyclic compounds–III: The conformations of some pinane derivatives
Authors: Abraham R. J. , Bottom F. H. , Cooper M. A. , Salmon J. R. , Whittaker D.
Published: May 2005

The 220 MHz 1H spectra of isoverbanone, nopinone and verbanone are reported.

The spectra of the first two are completely assigned but that of verbanone only partially. The coupling constants obtained provide information about the conformation of these molecules. The isoverbanone molecule is almost Y shaped, but that of nopinone is between a Y shape and a half‐chair conformation with the six membered ring bent away form the gem dimethyl groups. These conformations are consistent with the known steric interactions in these molecules.
Applications of proton magnetic resonance spectroscopy to structural problems–XXXI Hindered internal rotation in 2‐dimethyl‐aminopyridine derivatives
Authors: Katritzky A. R. , Tiddy G. J. T.
Published: May 2005

ΔH‡ and ΔS‡ values for the restricted rotation of the dimethylamino groups in 5‐nitro‐and 3,5‐dinitro‐2‐dimethylaminopyridine and 4‐dimethylaminopyrimidine are reported and discussed.
Deceptive simplicity in NMR spectra of oriented molecules
Authors: Diehl P. , Khetrapal C. L. , Lienhard U.
Published: May 2005

The theory for deceptive simplicity in the NMR spectra of oriented molecules is discussed in terms of degeneracy of subspectra. The conditions for the degeneracy of AB, AB2 and AA′BB′ spectra leading to deceptive simplicity in the spectra of the type ABX, AB2X, AA′BB′X and AA′XX′ are reported.

It is shown that the conditions for deceptive simplicity are easily fulfilled for ABX, AA′BB′X and AA′XX′ cases. It is further demonstrated that deceptive simplicity is not so common in AB2X spectra.

The proton spectra of partially oriented 2,4,5‐trichloronitrobenzene (AB) and 2,6‐dibromo‐pyridine (AB2) are use to illustrate degeneracy and those of p‐chloro‐ and p‐bromo‐fluorobenzenes are reported to demonstrate deceptive simplicity.
A proton magnetic resonance study of complexes of pyridine, 2‐methylpyridine 3‐methylpyridine, 4‐methylpyridine, and 2,6‐dimethylpyridine with borane and boron trifluoride
Authors: Fratiello Anthony , Schuster Ronald E.
Published: May 2005

A variable temperature, proton magnetic resonance study has been made of complexes of pyridine, 2‐methylpyridine, 3‐methylpyridine, 4‐methylpyridine, and 2,6‐dimethylpyridine with borane and boron trifluoride. By lowering the temperature and slowing ligand exchange, separate resonance signals can be observed for bulk and complexed molecules of the base. A direct comparison of the complexing abilities of these ligands was made by studying them in pairs with borane or boron trifluoride. The complexing abilities, as estimated from the NMR data, decreased in the order: 4‐MePy > 3‐MePy > Py > 2‐MePy > 2,6‐MePy. This trend was interpreted in terms of steric effects and the basic strengths of these molecules towards boron trifluoride.
The proton magnetic resonance spectra of cyclopentadiene trimers at 220 MHz
Authors: Foster R. G. , McIvor M. C.
Published: May 2005

Detailed interpretations of the spectra of four of the possible isomeric cyclopentadiene trimers are given. It is shown that the geometry of the ring fusion can be determined by measuring the chemical shifts of the bridge protons and of the allylic proton on the cyclopentene ring 3a‐H.
Carbon‐proton coupling constants in α‐chlorostyrene‐α‐13C
Authors: Servis Kenneth L. , Casanova Joseph , Geisel Manfred
Published: May 2005

The two stereochemically distinct two‐bond carbon‐13‐ hydrogen coupling constants J(13CCH), for α‐chlorostyrene‐α‐13C have been shown to be of similar magnitude but opposite sign (−6.3 and +5.6 Hz). A simple additivity relationship which adequately reproduces all the reported J(13CCH) values for chloroethylenes has been found.
Etudes par RMN en serie heterocyclique–III. Non‐equivalence magnetique et inversion de l'azote dans une serie d'heteocycles pentagonaux diazotes, pyrazolines‐2 et 3, pyrazolidines et pyrazolidones
Authors: Elguero J. , Marzin C. , Tizané D.
Published: May 2005

La non‐équivalence de groupements éthyle, benzyle et isopropyle fixés sur les azotes de pyrazolines‐2 et 3, de pyrazolidines et de pyrazolidones est fonction de l'asymétrie existant dans la molécule. Celle‐ci peut provenir soit d'un carbone du cycle, soit de l'un des azotes rendu asymétrique par protonation, quaternarisation ou simplement par ralentissement de son inversion, Ce dernier phénomène n'a été observé que dans le cas des pyrazolidines (possibilité d'inversion de deux azotes adjacents) et des pyrazolidones (inversion de l'azote non amidique): il est fonction des substitutions et des variations de température.
The 19F chemical shift in oxygen containing carbon fluorine products
Authors: Ciampelli F. , Venturi M. Tacchi , Sianesi D.
Published: May 2005

We have examined the 19F NMR spectra of a number of oxygen‐containing fluorocarbon products and obtained a comprehensive set of 19F chemical shift values, which enabled us to determine the influence of an oxygen atom bonded to a fluorocarbon group on the 19F chemical shift. The influence of neighbouring fluorocarbon groups, either directly connected or separated by an oxygen atom, was also considered.

Our results may be summarized as follows. An oxygen atom bonded by a single bond (ether type bond) to a fluorine substituted carbon atom decreases the 19F chemical shift, as does the introduction of a further fluorine atom. Considering two adjacent fluorocarbon groups, a variation of x ppm in the 19F chemical shift of one of the two groups gives a variation of 0·12 x ppm in the opposite sense on the 19F chemical shift of the other group. If the two groups are connected by an ether oxygen atom, the effect is only about 0·06 x ppm.
On the nuclear magnetic resonance spectrum of reduced nicotinamide adenine dinucleotide
Authors: Hollis Donald P.
Published: May 2005

The two C‐4 protons of reduced nicotinamide adenine dinucleotide (NADH) produce an AB NMR spectrum at 100 MHz as well as at 220 MHz. This observation allows an upper limit of 50 sec−1 to be placed on the mean rate of interconversion of the two folded forms of NADH invoked to account for the magnetic non‐equivalence of the C‐4 protons. The interpretation of non‐equivalence of the C‐4 protons in terms of the various equilibria among folded and unfolded forms of NADH and its possible significance in the mechanism of action of dehydrogenase enzymes is discussed. It is suggested that one folded form of NADH is strongly favored thermodynamically over the other and that the resulting magnetic non‐equivalence of the C‐4 protons is of doubtful significance in explaining the stereospecificity of dehydrogenase enzymes toward the nicotinamide ring.
Nuclear magnetic resonance studies of 5,6‐dicarboxy‐2‐norbornene derivatives
Authors: Kamezawa Norimasa , Sakashita Kiyoshi , Hayamizu Kikuko
Published: May 2005

A detailed study has been made on the 1H nuclear magnetic resonance (NMR) spectra of 5,6‐dicarboxy‐2‐norbornene derivatives, whose chemical shifts and geminal, vicinal and long‐range spin‐spin coupling constants were determined. Each signal of the spectra of these derivatives shows a slight low‐field shifts compared with norbornene itself. In the case of five methyl esters studied in this work, the signal of the 7s‐proton remains at approximately the same position in all the compounds, but that of the 7a‐proton is more variable. For the chemical shifts of the 7a‐proton of the five methyl esters, an additive rule seems to hold: that the magnitude of the low‐field shift, from the 7a‐signal of norbornene itself, is obtained by adding each of the effects of the carboxyl and the carbomethoxy groups substituted at the endo‐5‐(or 6‐) or the exo‐5‐(or 6‐) positions of the norbornene ring. In most of the derivatives considered in this work, the spin‐spin coupling constants, except those between bridgehead and bridged methylene protons, are about 1 to 2 Hz smaller than those of many other norbornene derivatives already studied. This fact seems to suggest that norbornenes, which have two bulky adjacent substituents at 5‐ and 6‐positions, may suffer distortions in the norbornene ring.
Die Kernresonanzspektren von N‐substituierten 2.6‐Dimethylmorpholinen
Authors: Brügel W.
Published: May 2005

Die NMR‐Spektren von am N substituirten 2.6‐Dimethylmorpholinen warden nach gaschromatographischer Trennung der Stereoisomren aufgenommen. Die spektralen Parameter warden daraus durch eine mathematische Analyse erthakten. Auf bisher ungklärte Besonderheiten der Spektren der cis‐Isomeren wird hingewiesen. Die Differenz der chemischen Verschiebung der 3‐ständigen Protonen der cis‐Isomeren erweist sich stark von dem N‐Substituenten abhängig.
Protonenresonanz‐Spektroskopie Ungesättigter Ringsysteme—XIV: Zur Frage der Substituenten‐Einflüsse auf die Resonanzfrequenzen und Vicinalen Kopplungskonstanten von protonen in substituierten Benzolen
Authors: Bremser Wolfgang , Günther Harald
Published: May 2005

Der Einfluß von Substituenten auf die Protonenresonanzen und die vicinalen H, H‐Kopplungskonstanten in Benzolderivaten wird mit Hilfe linearer Ausgleichsrechnungen untersucht. Für die relativ zur Protonenresonanz des Benzols auftretende Abschirmungsänderung Δσ bei der Substitution wird die Beziehung

angegeben, die eine Berechnung der Substituenten‐Effektes mit Hilfe des dipolaren und quadratischen Feldeffektes (Ez, E2) und der π‐Ladungsdichte‐Änderung am benachbarten C‐Atom (Δρ) erlaubt.

Die vicinalen Kopplungskonstanten lassen sich mit der HMO‐π‐Bindungsordnung nicht korrelieren. Eine Ausgleichsrechnung unter Benutzung der bekannten Abhängigkeit der Kopplung von der Substituenten‐Elektronegativität liefert

wobei ΔEα und ΔEβ die durch Substitution bedingte Änderung der Elektronegativität in α‐ bzw. β‐Stellung zum betrachteten HCCH‐Fragment bedeuten.
Interpretation of NMR spectra from four‐membered rings
Authors: Whipple Earl B. , Evanega George R.
Published: May 2005

When as many as four vicinal couplings occur between four protons situated on three carbon atoms of a cyclobutane ring, one can employ the Karplus relation to assign the configuration of substituents at the remaining positions and make some inferences about the stereochemistry. Four examples are described; the spectra and data are analyzed.
Zur Kenntnis der NMR‐Daten der O2CCH2S‐Gruppe
Authors: Brink M. , Larsson E.
Published: May 2005

Die magnetische Nichtäquivalenz der Methylenprotonen in den Verbindungen HO2CCH2SR′ und RO2CCH2SR′ wurde untersucht und die Einwirkung der Substituenten auf die geminalen Kopplungskonstanten JAB diskitiert. Es zeigte sich, dass die geminalen Kopplungskonstanten der Methylenprotonen fast unabhängig von der Konstitution der Verbindugen und den verwendeten Lösungsmitteln waren. Die magnetische Nichtäquivalenz der Methylenprotonen war sowohl von der Konstitution wie vom Lösungsmittel abhängig.
The NMR spectra and conformations of dihydropyran derivatives—I: The conformations of 2‐alkoxy‐5,6‐dihydro‐α‐pyran‐6‐carboxylic esters
Authors: Achmatowicz O. , Jurczak J. , Konowal A. , Zamojski A.
Published: May 2005

On the basis of NMR spectra of trans‐ and cis‐2‐alkoxy‐5,6‐α‐pyran‐6‐carboxylic esters it was found that, at room temperature, the trans‐compounds exist exclusively in the conformation with equatorial carbalkoxy and pseudoaxial alkoxy groups. The cis‐isomers appear to be in conformational equilibrium between a form with equatorial carbalkoxy and pseudoequatorial alkoxy groups and that with axial and pseudoaxial substituents. In the latter case, the axial carbalkoxy group is bent out off its normal position by about 15°.
CNDO calculations of diamagnetic shielding in molecules
Authors: Sadlej Andrzej J.
Published: May 2005

An approximate procedure for the calculation of diamagnetic shielding in molecules is presented. The method proposed is based on the ‘complete neglect of differential overlap’ (CNDO) molecular wave functions and is formulated according to the zero differential overlap (ZDO) approximation. The results obtained with several CNDO‐type wave functions for diatomic and polyatomic molecules are in very good agreement with non‐empirical SCF calculations. The 14N diamagnetic shielding constants in several molecules were computed and some approximations usually adopted in the interpretation of 14N chemical shifts are critically discussed. It was shown that in some cases the observed 14N chemical shifts cannot be interpreted solely in terms of the paramagnetic contribution to the shielding constant.
Transferts Protoniques de Sels D'ammonium. Substitues—II: Vitesse D'inversion a L'azote Par la Methode de ‘Protonation Competitive’
Authors: Delpuech Jean‐Jacques
Published: May 2005

L'inversion de l'azote pyramidal d'une amine peut ětre ralentie, de manière calculable, par une protonation presque totale dans un milieu d'acidité variable. Un traitement théorique complet permet de calculer sa vitesse à partir de la durée de vie moyenne du sel d'ammonium déterminée par résonance magnétique nucléaire. On peut ainsi fixer les conditions de validité de la formule approchée de Saunders et Yamada: la vitesse de protonation de l'amine doit ětre largement supérieure à la vitesse d'inversion; la vitesse de déprotonation du sel d'ammonium peut, par contre, ětre quelconque. Au cas où l'in version se produit entre deux molécules isomères différentes, ce traitement fournit également le rapport, à l'équilibre, des concentrations des sels isomères correspondants.
Nuclear magnetic resonance studies on dipeptides
Authors: Conti F. , Pietronero C. , Viglino P.
Published: May 2005

Dipeptides of different amino acids have been studied by NMR in aqueous solutions at different pH values. The results obtained are discussed in terms of the different contributions to the chemical shift of the α‐CH protons.
Inequivalence Magnetique Due a la Presence d'un Atome de Phosphore Asymetrique ou Pseudo‐Asymetrique
Authors: Marty Raymond , Houalla Doureid , Wolf Robert , Riess Jean
Published: May 2005

Dans les phosphinates d'alcoyle RPH(O)OR′, la présence de l'atome de phosphore asymétrique induit des inéquivalences magnétiques au niveau de protons ou groupes méthyles géminés. Si le reste alcoxy OR' comporte lui aussi un atome de carbone asymétrique, la résonance magnétique de 31P et de 1H, permet de mettre en évidence la formation des deux diastéréoisoméres attendus, en proportions égales.

Par ailleurs, la résonance magnétique de 31P révèle le caractère de centre de pseudo‐asymétrie de l'atome de phosphore dans les esters phosphoneux de l'alcool butylique secondaire.
Chemical shift non‐equivalence of ring protons in N‐substituted β‐lactams
Authors: Vigevani A. , Gioia B. , Gallo G. G.
Published: May 2005

A study is reported on the chemical shift non‐equivalence of the diastereotopic protons at C‐4 in identically 3,3‐disubstituted β‐lactams having an asymmetric carbon atom in positions ranging from β to ε of the chain attached to the nitrogen atom. The non‐equivalence has been correlated with the nature of the substituents bonded to the chiral centre and to its distance from the C‐4 protons.
Conformational analysis and J(HCOH) of α‐hydroxy‐N‐caproylhydrazobenzene, a degradation product of phenylbutazone
Authors: Neville G. A. , Awang D. V. C.
Published: May 2005

—Intramolecular OH… N hydrogen bonding between the hydroxylic and terminal amino groups of α‐hydroxy‐N‐caproylhydrazobenzene (5) permits J(HCOH) to be observed in most solvents. The configuration and conformation of 5 are discussed and an HCOH dihedral angle (ϕ) of 145° is calculated. Solvent effects on J(HCOH) as well as the role they appear to exert in restricting internal rotation of the phenyl substituents of 5 are discussed.
The proton resonance spectra of heterocycles—VI: The correlation of substituent effects on chemical shifts in bicyclic compounds
Authors: Katritzky A. R. , Takeuchi Y. , Ternai B. , Tiddy G. J. T.
Published: May 2005

The proton chemical shifts are reported for monosubstituted naphthalenes, quinolines and quinoxalines. Together with literature data, these chemical shifts are compared with the parent compounds and substituent effects evaluated statistically. The effect of substituents parallels that in benzenes, but is modified by bond fixation, steric hindrance and other effects which can, at least qualitatively be understood. The treatment enables estimation of likely chemical shifts for ABC spectra in fused aromatic systems which should facilitate the solution of such spectra.
NMR experiments on acetals—XXV: Conformational energy for the chair‐twist interconversion of the 1,3‐dioxane system
Authors: Anteunis M. , Swaelens G.
Published: May 2005

Trans‐4‐t‐Bu‐6‐R‐1,3‐dioxanes (R = Me, Pri and cyclohexyl) show temperature‐dependent values for 2J(H—2) and 3J(H—4(6), H—5) in their PMR spectra. This is the result of the presence of twist‐boat conformations. With the aid of typical limit‐values of 2J(H—2) for the chair and twist forms, the amount of flexible conformations were determined as a function of temperature (Table 2), allowing the determination of the enthalpy change for chair‐twist interconversion in 1,3‐dioxane itself (6·2 ± 0·3 kcal/mole). Typical values for 2J(H—2) were obtained from a study of low temperature spectra and from appropriate model compounds of which 4‐(1′‐adamantyl)‐6‐t‐Bu‐1,3‐dioxane served as the model for a genuine twist form with a twofold axis through C‐2/C‐5.
Determination of 2,4‐dichlorophenol in dichlorophenol isomers by NMR
Authors: Esumi Naohumi , Suzuki Teruo , Hayashi Shoichi
Published: May 2005

Quantitative analysis of isomers by NMR has been carried out in the measurement of species whose components present simple and sufficiently isolated spectra. Generally, the substituted aromatic proton splits into complicated spectral lines due to spin‐spin coupling. The ring proton spectra of dichlorophenol isomers show a pattern peculiar to the three spin system. It was found that some of the signal attributable to these compounds appear in a position slightly isolated from each other. Therefore, we established the quantitative analysis method for dichlorophenol, using the signal intensity method. From the result of the quantitative analysis, the lowest detectable concentration was 1·1% (±0·3% at the standard deviation). The accuracy of the peak intensity method was found to be ±1·8% within the 50 to 80 mol% concentration range of 2,4‐dichlorophenol isomer.
Determination de Susceptibilites Paramagnetiques par les Methodes de RMN
Authors: Widenlocher Mm. Gérard , Dayan Elie
Published: May 2005

Les susceptibilités magnétiques jouent un rǒle important en RMN, mais leurs valeurs ne sont pas toujours connues; ici, les auteurs donnent une méthode de mesure de susceptibilités paramagnetiques et proposent une explication pour la dépendance linéaire de la susceptibilité magnétique en fonction de déplacement observé.
Conformations of highly hindered aryl ethers—IV PMR studies of 2,4‐ and 2,6‐ dinitroaryl ethers
Authors: Lehmann F. Pedro A.
Published: May 2005

PMR studies of a series of 2,4‐ and 2,6‐ dinitrophenyl‐ and 2,4‐dinitronaphthyl‐ aryl ethers strongly indicate the existence of preferred conformations. Extensive conjugation of the ether linkage with the dinitro ring, resulting in their coplanarity, is an important stereochemical influence. In the ensuing skew conformation the dinitro ring is positioned in such a way that the 6‐substituent is proximal to the other ring. In the case of the 2,4‐dinitrophenyl ethers (1) this is the 6‐proton, which shows the expected shielding due to the ring current in the other ring. In the 2,6‐dinitrophenyl‐(2) and 2,4‐dinitronaphthyl‐(3) ethers, this is a nitro group, twisted out of coplanarity to fit over the other ring, whose magnetic anisotropy is reflected in the shielding experienced by the 6′‐protons. When there is a 2′‐substituent magnified image present the ring which bears it twists in such a way as to bring the 6′‐proton closer to the proximal nitro‐group, explaining the greater shielding observed in these cases. Variable temperature studies provided further evidence in favor of these conformations since no significant changes were observed from −55° to + 155°, even for compounds with four substituents flanking the ether linkage. Nevertheless, the compounds studied here are not frozen in these conformations, but probably inter‐convert via concerted rotation with others.
NMR studies of silver ion and 1,3,5‐trinitrobenzene complexes
Authors: Deb K. K. , Cole T. C. , Bloor J. E.
Published: May 2005

A study, using NMR techniques, of the propensity of complex formation of silver ions with hydrocarbons and heterocyclic compounds containing nitrogen, oxygen and sulphur is described. The results are compared with similar data using 1,3,5‐trinitrobenzene as an acceptor. The differences in the two sets of data are interpreted in terms of localized and delocalized interactions in the formation of weak complexes.
The NMR spectra of some fluorinated pyridine derivatives
Authors: Thomas W. A. , Griffin G. E.
Published: May 2005

The 1H and 19F spectra of a variety of mono‐ and di‐ fluorinated pyridines are examined, and compared with the corresponding spectra of the pyridinium ions. The magnitudes and signs of the 1H19F coupling constants are in general in accord with those observed for the corresponding 1H1H couplings, with an exaggerated range. Large changes in the NMR parameters are observed on protonation of the nitrogen, 3J(HF) changing sign in some of the α‐fluoropyridine derivatives.
Acetate‐methyl signals in the NMR spectra of peracetylated derivatives of chondroitin sulfates and their desulfated derivatives
Authors: Hirano Shigehiro
Published: May 2005

Chondroitin 4‐sulfate (Ch4S), chondroitin 6‐sulfate (Ch6S), dermatan sulfate, chondroitin and desulfated dermatan sulfate were peracetylated and the derivatives isolated in yields of 45 to 88%. Acetate‐methyl signals in the NMR spectra of these derivatives in D2O were analyzed using a correlation of the chemical shifts to the orientations. The lC conformation of hexopyranosiduronic acid moieties was estimated in these derivatives. No significant change of the chemical shifts was observed with the NMR spectra measured in D2O, in 7 M urea solution, in the various diluted solutions, and in the temperature range of 2 to 95° in D2O.
Linewidth variation in the dinitronitrosomethyl dianion radical in the slow exchange mode
Authors: Russell Glen A. , Norris Robert K.
Published: May 2005

The treatment of nitromethane or dinitromethane in aqueous alkaline solutions (1 to 2·5 M hydroxide) with nitrogen dioxide yields the dianion radical of dinitronitrosomethane [C(NO2)2(NO)\documentclass{article}\pagestyle{empty}\begin{document}$ \buildrel\textstyle.\over= $\end{document}] which at 30° has hfsc of a = 10·75 and 0·65 and aNNO = 5·80 g. Restricted rotation about the CNO bond causes magnetic non‐equivalence of the two nitro groups which can slowly exchange giving rise to line broadening. The use of 15N labeled nitrogen dioxide gave the dianion radical

which exists in two equally populated conformations, each of which shows the expected line broadening for a ‘slow exchange’ process in which the nitro groups are being interconverted.
Complete PMR analysis of naphthalene as an eight spin system
Authors: Crecely R. W. , Goldstein J. H.
Published: May 2005

The PMR spectrum of naphthalene has been completely analyzed as an eight‐spin system for the first time. It was found that inter‐ring long‐range couplings exist between all combinations of the α and β protons on adjacent rings. The signs and magnitudes of the coupling values have been determined and compared to couplings reported in the literature for other polynuclear compounds.
Protonenresonanzuntersuchungen an Polysacchariden—III: Amylose–und dextranderivate
Authors: Keilich G. , Siefert E. , Friebolin H.
Published: May 2005

Die Protonenresonanzspektren einiger Methyl‐, Acetyl‐ und Benzoylderivate der Polysaccharide Amylose und Dextran sowie der α‐D‐Glucose und β‐Maltose wurden analysiert. Aus den relativen Signallagen und den Kopplungskonstanten der Ringprotonen kann die Konfiguration und Konformation des Monomerbausteins sowie die Art der glycosidischen Bindung bestimmt werden.
Etude des Signes des Constantes de Couplage 3J(PXCH) et 4J(FPXCH) dans les Diaza‐, Dioxa‐ et Dithiaphospholanes Fluores
Authors: Albrand J.‐P. , Cogne A. , Gagnaire D. , Martin J. , Robert J.‐B. , Verrier J.
Published: May 2005

On a réalisé l'analyse complète des spectres de RMN des fluorophospholanes (1 à 3). Les signes absolus des constantes de couplage 3J(PH) et 4J(FH) ont été déterminés, par rapport au signe absolu connu de la constante 1J(PF), à partir d'expériences de double résonance hétéronucléaire sélective. Les constantes 3J(POCH) et 3J(PNCH) observées sont toutes positives. Les deux constantes 3J(PSCH) du dithiaphospholane (2) présentent des faibles valeurs de signes opposés, la plus grande étant positive. Toutes les constantes 4J(FPXCH) sont positives et ces constantes semblent peu stéréospécifiques.
Tritium nuclear magnetic resonance spectroscopy—I: Technique, internal referencing and some preliminary results
Authors: Bloxsidge J. , Elvidge J. A. , Jones J. R. , Evans E. A.
Published: May 2005

Routine measurement of triton magnetic resonance spectra is described for the first time, using a micro‐bulb sample tube assembly to obviate radiological hazards. Levels of isotope abundance and chemical concentration, the problem of self‐radiolysis and the general usefulness of the technique are discussed. Results are given for a selection of compounds including glucose, amino‐acids, thymidine and uridine. The self‐radiolysis of the last is followed.
The detection of hidden proton magnetic resonance signals by means of INDOR
Authors: van Deursen F. W.
Published: May 2005

The INDOR technique appears to be a very useful and rapid tool for the detection of hidden proton lines as an aid in the elucidation of the structure of complex organic molecules. The experimental conditions for obtaining optimum results in a limited time are discussed. Analysis of the INDOR spectra of a number of selected spin systems are given; these show the capabilities of this method. Examples are given in which this technique is applied.
Chemical shift non‐equivalence of methylene protons adjacent to an asymmetric nitrogen atom
Authors: Vigevani A. , Gioia B. , Cavalleri B. , Gallo G. G.
Published: May 2005

The chemical shift non‐equivalence of the methylene protons adjacent to the quaternary nitrogen in compounds of the type has been investigated. The behaviour of the examined compounds is interpreted in terms of different rotation rates around the three CN⊕ bonds. The vicinal and geminal coupling constants of the non‐equivalent methylene protons are also reported and discussed in terms of steric factors.
An abnormal trend in J(13CCH) values in some aldehydes
Authors: Ewing D. F.
Published: May 2005

The 2J(13CCH) couplings involving the formyl proton of α‐halogeno‐aldehydes have been found to decrease with increasing halogen electronegativity. This trend may be rationalised in terms of inductive withdrawal and a conformation dependent hyperconjugative effect. The direct J(13CH) couplings are also anomalous.
Solvent effects in NMR spectra induced by benzene in methyl benzoic esters—IV
Authors: Alexandrou N. E. , Hadjimihalakis P. M. , Pavlidou Miss E. G.
Published: May 2005

NMR solvent effects induced by benzene in methyl substituted benzoic esters can be effectively used in the interpretation of complex NMR spectra. A 1:1 collision complex between solvent and solute is proposed, supported by dilution curve experiments and the geometry of the ‘complex’ is discussed.
Intensitätsformel für Hyperfeinstrukturlinien bei n aequivalenten Kernen mit beliebigem Spinmoment—I
Authors: Kuss E. , Brehm U.
Published: May 2005

Die relativen Intensitäten der kernmagnetischen Hyperfeinstrukturlinien sind bei n aequivalenten, benachbarten Protonen (I = ½) bekanntlich durch die Binomialkoeffizienten und das Pascalsche Dreieck gegeben. Bei n aequivalenten, benachbarten Kernen mit I > ½ ist eine einfache Berechnungsformel für die relativen Intensitäten nicht bekannt, andrerseits ist die Ermittlung der sehr großen Zahlen aus den Anordnungsmöglichkeiten der Spins sehr umständlich.

Ordnet man die Zahlen wiederum in n Reihen an, so erhält man ‘Pascalsche Dreiecke höherer Ordnung’. Sie sing (a) symmetrisch, (b) Die Summe der Zahlen der n‐ten Reihe ist stets (2I + 1)n und (c) Es ergibt sich jede Zahl in irgendeinem der Dreiecke als Summe der r darüberstehenden Zahlen, wobei r = 2I + 1 ist.

Für die Berechung der v‐ten Zahl in der n‐ten Reihe eines beliebigen Dreiecks höherer Ordnung wird eine Rekursionsformel angegeben.

Weitergehend wird gezeigt, daß auch eine direkte Berechnung, ohne Kenntnis der Zahlen der voraufgehenden Reihe, bei beliebig hohen Werten von n und I aus der Beziehung:

möglich ist. Darin ist a die größte ganze, psotive Zahl ≦(v – 1)/r und ≦n.

Unter der Voraussetzung, daß die Hyperfeinstruktur‐Aufspaltung J klein gegenüber der chemischen Verschiebungsdifferenz Δν* ist, lassen sich die relativen Intensitäten der Hyperfeinstrukturlinien aus der Formel in sehr einfacher Weise berechnen, wie an einigen Beispielen gezeigt wird.
Structure des Complexes de Meisenheimer Complexes de Courte Duree de Vie et Complexes Stables Formes par Action des Ions Méthoxydes sur les Dinitro‐4,6 Anisoles X‐2 Substitues
Authors: Terrier François , Hallé Jean‐Claude , Simonnin Marie‐Paule
Published: May 2005

L'étude RMN de l'interaction des ions CH3O− avec les dinitro‐4,6 anisoles X‐2 substitués (X = CN, CF3, Cl, F) a permis d'identifier divers complexes de Meisenheimer résultant de l'attaque des ions CH3O− sur les carbones −5 et −3 non substitués. Ces complexes −1,5 et −1,3, dont la durée de vie est très courte, se transforment rapidement au profit des complexes stables −1,1. Les déplacements chimiques des anisoles et des différents complexes reflètent les effets électroniques et stériques des substituants X. L'influence de la charge négative portée par le cycle et les modifications géométriques du squelette sont mises en évidence en comparant les paramètres RMN des anisoles et des complexes correspondants. Lorsque X = F, l'étude des signes des constantes de couplage montre que 3J(FH) et 5J(FH) sont de signes contraires dans l'anisole et dans le complexe −1,1.
The fluorine magnetic resonance spectrum of poly(vinyl fluoride)
Authors: Weigert F. J.
Published: May 2005

High resolution fluorine magnetic resonance spectra have been obtained for poly(vinyl fluoride) at elevated temperature. Proton noise‐decoupling and time‐averaging techniques have given new tacticity and sequence information.
NMR spectra of the cycloaddition adducts between tetracyanoethylene oxide and norbornadiene derivatives
Authors: Shen Kei‐Wei , Shen Yvonne Hua , Winters Lawrence J.
Published: May 2005

The NMR spectra of the cycloaddition adducts between tetracyanoethylene oxide (TCNEO) and norbornadiene derivatives have been studied. It was shown that there was significant long‐range coupling between 7‐anti and endo hydrogens in the adducts and that this long‐range coupling was solvent dependent. Based on the present study it is concluded that the long‐range coupling between endo and anti hydrogens can be as high as 4·1 Hz when an electronegative substituent is attached to the carbon which bears endo hydrogen.