bluuebunny/crossref_metadata_2025 huggingface dataset:
Korrosionsprobleme in den Ölfeldern von Belayim
Authors: Azzam A. M. , Mohsen E. E.
Published: May 2005

Zur Ermittlung der Aggressivität des im Ölfeld von Belayim benutzten Flutungswassers wurden Labor‐ und Feldversuche durchgeführt. Dabei wurden der Einfluß von Sauerstoffgehalt, Strömungsgeschwindigkeit sowie Betriebs‐ und Stillstandszeiten auf die Korrosionsgeschwindigkeit untersucht. Die Korrosion ist am geringsten, wenn alle diese Variablen auf einem möglichst geringen Wert gehalten werden (Strömungsgeschwindigkeit 0,5 m–sec, Sauerstoffgehalt 0,5 ppm, Betriebszeit 30% der Gesamtzeit), was jedoch unwirtschaftlich ist. Stärkste Korrosion tritt auf bei hoher Sauerstoffkonzentration (ab 5 ppm) und hohem Anteil der Betriebszeit.
Einflußgrößen der H‐induzierten Spannungsrißkorrosion bei niedriglegierten Stählen
Authors: Pöpperling R. , Schwenk W.
Published: May 2005

Bei Einwirkung H2S‐haltiger wäßriger Medien treten neben oberflächennahen Blasen im Bereich von scharfkantigen Einschlüssen Innenrisse (HIC) und bei Vorliegen von Zugspannungen kleine transkristalline Mikrorisse quer zur Zugspannung auf, Nur die letzten führen zur Spannungsrißkorrosion. HIC‐beständige Stähle haben einen hohen Reinheitsgrad, aber keine erhöhte Beständigkeit gegen Spannungsrißkorrosion. Bei Röhrenstählen mit Streckgrenzen bis 600 N mm−2 ist die kritische Zugspannung für Spannungsrißkorrosion der Streckgrenze proportional. In H2S‐Lösung von pH 3 gibt es bei verschieden niedriglegierten und gewalzten Stählen keine Korrelation zwischen Standzeit und Streckgrenze. Im allgemeinen wird die Anfälligkeit durch abnehmende pH‐Werte und durch kathodische Polarisation erhöht, während die Temperatur um 20° C ein Anfälligkeitsmaximum bewirkt.
Über den Einfluß des aufgenommenen Wasserstoffs auf die Wechselbiegefähigkeit von Kohlenstoffstahl bei der Beizung in Schwefelsäure
Authors: Grubitsch H. , Hilbert F. , Künne P.
Published: May 2005

Bei der Schwefelsäurebeizung (1 M, 50° C) von Stahlproben St 3 GBKL wurden in Abhängigkeit von der Beizdauer die abgetragene Metallmenge (Gewichtsverlust), die aufgenommene Wasserstoffmenge (durch Warmauslagerung) und die Abnahme der Wechselbiegefestigkeit (konventioneller Biegeversuch bei 25 Hz und ± 5° Auslenkung) gemessen. Aus den experimentellen Daten wurden die lineare Korrosionsgeschwindigkeit zu 21 · 10−6 kg · m−2 · sec−1, die Sättigungskonzentration an Wasserstoff zu 8, 76 ppm (= 9,81 ml/100 g) und der Diffusionskoeffizient des Wasserstoffs im Stahl zu 8, 74 · 10−7 · cm2 · sec−1 bestimmt. Die Biegezahl wird nicht nur durch die integrale Menge des aufgenommenen Wasserstoffs beeinflußt, sondern hängt auch von dem Konzentrationsprofil des Wasserstoffs in der Probe ab; eine Hypothese zur Erklärung dieses Sachverhaltes wird vorgelegt.
Elektrochemische Untersuchung der Permeabilität, Adhäsion und Inhibitorwirkung von Plasmapolymerschichten auf Edelmetallelektroden
Authors: Doblhofer Karl , Eiselt Irmgard
Published: May 2005

Zur Charakterisierung des Verbundsystems Plasmapolymer/Metall wurden Elektroden in einem Acrylnitril/Argon Plasma beschichtet und in wäßrigen Medien mit elektrochemischen Methoden untersucht. Um Veränderungen der Metallseite auszuschließen, wurden Edelmetallelektroden verwendet. Aus Wechselstrommessungen mit den beschichteten Platinelektroden in Schwefelsäure konnte die elektrische Ladung bestimmt werden, die der Elektrosorption von Wasserstoff an freiem Platin entspricht. Dies ist ein Maß für den Anteil der Pt‐Oberfläche, der für den Elektrolyten zugänglich ist. Kurz nach dem Eintauchen wurden etwa 0,01–1% derartig „freier”︁ Oberfläche nachgewiesen; mit der Zeit nahm dieser Anteil regelmäßig zu. Es wird gezeigt, daß die Schichten Membraneigenschaften haben. Somit läßt sich die Grenzfläche Metall/Polymer auch durch noch fest haftende Schicht hindurch analysieren. Insbesondere kann die zeitliche Zunahme der für den Elektrolyten zugänglichen Platinoberfläche, d.h. das Aufbrechen der Platin‐Polymerbindungen als Funktion der Herstellungsbedingungen verfolgt werden.
Untersuchungen zum Emaillieren von Nickelbasislegierungen
Authors: Renner M. , Köhler M. , Ernst E. , Spang M.
Published: May 2005

Emaillierte Chemieapparate haben in der Chemietechnik bei der Handhabung hochkorrosiver Produkte einen hohen Stellenwert als wirtschaftliches Korrosionsschutzverfahren.

Bislang wurden als Trägerwerkstoff ausschließlich un‐ bzw. niedriglegierte warmfeste Stähle verwendet. Diese aus Kosten‐und Festigkeitsgründen ausgewählten Stähle besitzen jedoch keine Korrosionsbeständigkeit in aggressiven Medien, wenn der Emailüberzug bei unsachgemäßer Handhabung großflächig geschädigt worden ist. Ausgehend von der Überlegung, hochkorrosionsbeständige Nickelbasislegierungen als Trägerwerkstoff für den Email‐überzug für den Druckbehälterbau einzusetzen, wurden umfangreiche Untersuchungen über das Eigenschaftsprofil der neuen Verbundsysteme durchgeführt und Druckbehälter (4 l‐Maßstab) hergestellt, zugelassen und betrieben.

Über die Untersuchungsergebnisse der mechanisch‐technologischen Werte, das Korrosions‐ und Emailverhalten wird berichtet.
Cleaning of two hundred year‐old copper works of art using citric acid with and without benzotriazole and 2‐amino‐5‐mercapto‐1,3,4‐thiadiazole
Authors: Otero E. , Bastidas J. M.
Published: May 2005

This paper studies the use of 5% (wt) citric acid without inhibitor, inhibited with benzotriazole (BTA) and 2‐amino‐5‐mercapto‐1,3,4‐thiadiazole (AMT) and de‐aerated with nitrogen in the cleaning of 18th and 19th century chalcographic plates. DC and AC electrochemical techniques have been used to characterize the effect of the inhibitors and to quantify the aggressiveness of the cleaning treatment.

Citric acid removes copper surface tarnish. BTA and AMT inhibitors are similarly efficient. De‐aeration reduces corrosion to levels similar to those obtained with inhibitors.
Low Surface Energy Perfluorooctyalkyl Acrylate Copolymers for Surface Modification of PET
Authors: Saïdi Salima , Guittard Frédéric , Guimon Claude , Géribaldi Serge
Published: May 2005

Summary: Copolymers of ω‐perfluorooctyalkyl acrylate C8F17‐(CH2)n′OC(O)CHCH2 with butyl acrylate were prepared by free radical polymerization. These compounds were characterized by 1H and 19F NMR spectroscopy. Thermal properties were evaluated by DSC and TGA analysis. By changing the fluorinated monomer structure, i.e., the length of the hydrocarbon spacer between the perfluorinated side chain and the ester function, and the concentration of the perfluorooctyalkyl acrylate monomers, the surface properties of the resulting copolymers were greatly influenced. The copolymers exhibited low surface energies, the lowest recorded being 6 mJ · m−2. XPS analysis indicated fluorine enrichment at the polymer‐air interface.

Molecular structure of the synthesized copolymer.

image

Molecular structure of the synthesized copolymer.
Donor‐Embedded Polybinaphthalenes for Nonlinear Optical Applications: Influence of the Incorporation of a Double Bond
Authors: Koeckelberghs Guy , De Groof Leen , Picard Isabel , Verbiest Thierry , Persoons André , Samyn Celest
Published: May 2005

Summary: In this paper two new donor‐embedded polybinaphthalenes prepared by the Heck reaction are presented. By introducing a double bond in the polymer backbone, the supramolecular structure was altered in comparison with polymers without the double bond. Comparison between the CD/UV‐Vis spectra of polymers, with and without the double bond (previously synthesized in our laboratory) proved this change in a supramolecular structure. The double bonds also allow crosslinking upon heat treatment. NLO experiments demonstrated a more stable nonlinearity over time depending on the degree of crosslinking.

magnified image
New Poly(arylene ethynylene)s Consisting of Electron‐Deficient Aryleneimide Units
Authors: Witzel Silke , Ott Christina , Klemm Elisabeth
Published: May 2005

Summary: A new class of poly(arylene ethynylene)s (PAEs) containing an electron‐deficient N‐alkylphthalimide unit was prepared by means of a Sonogashira reaction. Complete solubility of the PAEs was observed by utilizing a 2,6‐diisopropylphenyl side chain. The chemical structure of the novel soluble polymer 3c was confirmed by NMR spectra, whereas the insoluble polymers were characterized by elemental analysis and IR spectra. Fluorescence measurements of 3c indicate a rigid structure and high symmetry in the excited state.

magnified image
Linear‐Hyperbranched Amphiphilic AB Diblock Copolymers Based on Polystyrene and Hyperbranched Polyglycerol
Authors: Barriau Emilie , García Marcos Alejandra , Kautz Holger , Frey Holger
Published: May 2005

Summary: A convenient three‐step strategy has been developed for the preparation of well‐defined amphiphilic, linear‐hyperbranched block copolymers by hypergrafting. The synthetic procedure is based on a combination of carbanionic polymerization with the alkoxide‐based, controlled ring‐opening multibranching polymerization of glycidol. A linear AB diblock copolymer polystyrene‐block‐polybutadiene (PS‐b‐PB) with narrow polydispersity was obtained by anionic copolymerization. Subsequent hydroxylation by hydroboration led to PS508‐b‐(PB‐OH)56, used as macroinitiator for the polymerization of glycidol under slow monomer addition conditions.

Structure of the linear‐hyperbranched amphiphilic AB diblock copolymer PS508‐b‐(PB56‐hg‐PGx) and an AFM micrograph of its micellar core–shell structure observed after solution casting.

magnified image

Structure of the linear‐hyperbranched amphiphilic AB diblock copolymer PS508‐b‐(PB56‐hg‐PGx) and an AFM micrograph of its micellar core–shell structure observed after solution casting.
Abrasiver Verschleiß nitrocarburierter Stähle
Authors: Al‐Rubaie K. S. , Pohl M. , Steinmeier F.
Published: May 2005

Diffusionsschichten werden in großem Umfang industriell genutzt, um die tribologischen Eigenschaften von Bauteilen zu verbessern.

In dieser Arbeit wurde der abrasive Verschleiß verschiedener Diffusionsschichten untersucht. Dazu wurden drei Diffusionsverfahren ausgewählt, nämlich Salzbad‐, Gas‐ und Plasmanitrocarburieren, die an fünf verschiedenen Stählen zur Anwendung gelangten. Die Stähle waren St 52‐3, Ck 45, 42 CrMo 4, 30 CrNiMo 8 und X 20 Cr 13. Die Schichtdicken und deren Porositäten wurden mit Hilfe der Lichtmikroskopie untersucht. Der Schichtaufbau wurde mittels der Röntgenfeinstrukturanalyse und die Oberflächen‐Kenngrößen mit Hilfe des Tastschnittverfahrens bestimmt. Die Oberflächenhärte und der Härteverlauf wurden mit dem Vickers‐verfahren ermittelt. Der Verschleißtest wurde nach dem Schleifpapierverfahren durchgeführt. Die vorherrschenden Verschleißmechanismen wurden mittels Rasterelektronenmikroskopie dokumentiert.

Es stellte sich heraus, daß alle Schicht/Substrat‐Kombinationen eine Verbesserung des abrasiven Verschleißwiderstandes bewirkten. Im allgemeinen verringerte sich der Verschleißbetrag bei zunehmender Härte und größerer Schichtdicke. Als beständigste Schicht/Substrat‐Kombinationen gegen abrasiven Verschleiß stellten sich salzbad‐, und gasnitrocarburierte Stähle vom Typ X 20 Cr 13 heraus, während die plasmanitrocarburierten Proben aus den Werkstoffen St 52‐3 und Ck 45 am schlechtesten abschnitten.
Sintern von TiO2 im Mikrowellenfeld
Authors: Bossert J. , Ludwig C.
Published: May 2005

Am Technischen Institut der Friedrich‐Schiller‐Universität Jena ist eine Mikrowellen‐Sinteranlage erstellt worden, die in einer Kammer eine kombiniert. Zusätzlich wurde in die Anlage ein Dilatometer integriert, welches die Messung der Schwindung bzw. Ausdehnung der Proben ermöglicht. Diese Apparatur erlaubt einen zuverlässigen Vergleich des Materialverhaltens bei konventioneller und bei Mikrowellenerwärmung.

Am Beispiel von TiO2 konnte nachgewiesen werden, daß das Ankopplungsverhalten und das Sinterverhalten der Probe durch Messung der Temperatur und der Schwindung reproduzierbar beurteilt werden kann. Probekörper aus TiO2 mit einer Gründichte von ca. 60% der theoretischen Dichte nehmen ab einer Temperatur von 940°C effizient Mikrowellenenergie auf wobei Aufheizraten von über 300 K/Min gemessen wurden. Bei einer Temperatur von 1360°C wurden innerhalb von 40 Minuten Enddichten von 98% der theoretischen Dichte erreicht. Im Vergleich mit konventionell gesintertem TiO2 (1400°C, drei Stunden) ergibt sich ein deutlich feinkörnigeres Gefüge.
Electrochemically Activated Glassy Carbons as potential Supercapacitors and substrates for fixed mediators
Authors: El‐Rahman H. A. Abd
Published: May 2005

Glassy carbon electrodes were prepared in various electrolytes by cyclic voltammetry and constant potential methods under various conditions to explore the factors affecting the response of GC after the electrochemical pretreatment (ECP), including the high pseudo‐capacitance, the great ability to absorb and strongly hold redox species and the facilitation of kinetics of electron transfer. Deepening the oxidation via increasing the oxidation potential and the oxidation time or the number of cycles and the final potential in cyclic voltammetry were found to increase the amount of redox species loaded onto GC and the pseudocapacitance due to formation of thicker carbon oxide layer. The increase in the rate of electron transfer reactions on deepening the oxidation is, however, attributed to the generation of more cleaner surface and more reactive sites. The order of increasing the efficiency of ECP; NaOH>KCl>HCl>NaClO4(MeCN), signifies the role of water and pH on the formation and thickness of the oxide layer formed after ECP. The results support the predominance of the faradaic origin of the pseudo‐capacitance of GC after ECP.
Determination of single PCB congeners in fish by on‐line LC‐GC
Authors: Hyvönen Helena , Auvinen Tuula , Riekkola Marja‐Liisa , Himberg Kimmo
Published: May 2005

An on‐line coupled LC‐GC technique was applied to the analysis of polychlorobiphenyls (PCBs) in Baltic herring. The liquid chromatographic (LC) and gas chromatographic (GC) instruments were coupled with a loop‐type interface and concurrent solvent evaporation was used in transferring the sample to the GC. A cyano phase with hexane as eluent was used for the LC separation and an NB‐54 column was used for the GC separation. On‐line LC‐GC is a good alternative to GC for the analysis of PCB compounds in biological material. The number of sample propurification steps is fewer and, the risks of sample contamination and loss are reduced.
Conformation and intermolecular interation of the antidepressant drugs nitroxazepine and imipramine in aqueous solutions and model membranes
Authors: Srivastava Sudha , Phadke Ratna S. , Govil Girjesh , Nagarajan K.
Published: May 2005

Complete assignments of the proton magnetic resonance spectra of nitroxazepine and imipramine have been made using 1D and 2D techniques. The drugs are found to aggregate through stacking intereactions between the tricyclic moieties at higher concentrations in aqueous solutions. The changes in the chemical shifts with increasing concentration of the two antidepressant drugs show qualitative agreement with the stacking patterns and conformations observed in crystal structures. The conformations of the propyl moiety of the two drugs in aqueous solution and in lipid bilayers are very different. In D2O, the drugs exist in an extended chain conformation which is similar to the crystal structure. In lipid bilayers they acquire a folded structure. The folded structures probably facilitate the binding of the hydrophobic regions of the drugs to the interior of lipid bilayers.
A substituent chemical shift (SCS) effect study by 13C and 19F NMR of para‐substituted phenylhalodiazirines
Authors: Terpinski Jacek , Denney Dorothy Z. , Beveridge Richard , Cox D. Phillip , Moss Robert A.
Published: May 2005

A range of 3‐(para‐substituted‐phenyl)‐3‐halodiazirines have been prepared and their 13C and 19F NMR spectra measured. Calculated with these data were the susceptibility coefficients ρI and ρR of the inductive (σI) and resonance (σR0) effects, respectively, to substituent‐induced chemical shift differences at the diazirine carbon (13C NMR) and the 3‐fluorine (19F NMR of the 3‐fluorodiazirine series). An inverse relationship was found between the susceptibility parameters and the electronegativity of the halo substituent at the diazirine carbon.
Long‐range two‐dimensional heteronuclear chemical shift correlation
Authors: Martin Gary E. , Zektzer Andrew S.
Published: May 2005

Long‐range heteronuclear chemical shift correlation has undergone a period of burgeoning growth during the past 4 years. Initially, such correlations were made by simply reoptimizing the conventional heteronuclear chemical shift correlation sequence originally devised by Freeman and Morris. Problems inherent in the reoptimization of the Freeman–Morris sequence have led to the development of a number of other of experiments, most recently, including reverse (proton) detected heteronuclear multiple quantum techniques. The techniques now in use are compared and the inherent problems of each are identified and weighed against advantages. Applications of each technique are also presented.
Comparative study of the 13C nuclear magnetic resonance shifts of carbonyl and thiocarbonyl compounds
Authors: Katritzky Alan R. , Sobiak Stanislaw , Marson Charles M.
Published: May 2005

The 13C spectra of nine novel and fifteen known derivatives YC(:X)Z with X = O or S are reported and compared with literature data. Two linear relationships between 13CO and 13CS are established depending on whether or not Y or Z is linked through an O atom to the CX group. General equations for 13CO and 13CS in terms of the attached groups are also deduced. The 13C chemical shifts of n‐butyl and n‐octyl groups attached to the heteroatoms in this series of compounds are recorded and discussed.
Chemistry of the SO bond. 10—Conformational analysis of cyclic sulphates via 13C and 17O NMR spectroscopy
Authors: Hellier Desmond G. , Liddy H. G.
Published: May 2005

The conformational analysis of cyclic sulphates with 5–7‐membered rings is discussed on the basis of 13C and 17O NMR spectroscopic studies.
1H and 13C NMR studies of third‐generation cephalosporin esters sulphoxides and sulphones
Authors: Lee Moses , Micetich Ronald G. , Singh Rajeshwar , Spevak Paul , Singh Maya Prakash , Maiti Samarendra N.
Published: May 2005

The 1H and 13C NMR signals of 13 third‐generation cephalosporin esters have been assigned, and the effects of the sulphoxide and sulphone groups on the chemical shifts are discussed.

Cephalosporin ester sulphoxides and sulphones 13C NMR 1H NMR Stereochemistry.
Structural elucidation of germine esters isolated from Veratrum nigrum L. Total assignment of 1H and 13C nuclear magnetic resonances by two‐dimensional NMR techniques
Authors: Han Xiuwen , Grossmann Peter , Rüegger Heinz
Published: May 2005

The application of two‐dimensional phase‐sensitive COSY, ROESY and 13C–1H shift correlation spectroscopy in the structural elucidation and stereochemical assignment of the steroidal alkaloids 15‐(2‐methylbutyryl)germine, 3‐(2‐hydroxy‐2‐methylbutyryl)‐15‐(2‐methylbutyryl)germine and 16‐(2‐methylbutyryl)germine is reported. It is shown that two‐dimensional 13C–1H heteronuclear long‐range correlation spectroscopy is an invaluable method for the stereochemical assignment of proton resonances which overlap in 1H NMR and homonuclear correlation spectra.
1H NMR and molecular mechanics studies of epimeric ethyl esters of 20(R, S)‐hydroxy‐23‐norcholanoic acids
Authors: Maier M. S. , Seldes A. M. , Gros E. G.
Published: May 2005

Proton chemical shifts for the C‐18, C‐21, CO2CH2CH3 and CO2CH2CH3 protons of epimeric ethyl esters of 20(R,S)‐hydroxy‐23‐norcholanoic acids were measured in deuteriochloroform and pyridine‐d5. The observed solvent shifts due to specific OH—pyridine hydrogen‐bonded complexes allowed the quantification of the epimeric mixtures by analysis of the pyridine‐d5 1H NMR spectra. The main features of the pyridine‐induced shifts are rationalized in terms of the preferred conformations for the 20R‐ and 20S‐epimers, which are predicted by molecular mechanics calculations.
Carbon‐13 spin‐lattice relaxation of acetylcholine and analogues
Authors: Lambert Joseph B. , Schilf Wojciech
Published: May 2005

Carbon‐13 spin‐lattice relaxation times and nuclear Overhauser enhancements were measured for acetylcholine and several structural analogues, and interpreted in terms of segmental motion and aggregation.
Paramagnetic resonance in bipyridyl adducts of copper(II) salicylhydroxamates
Authors: Khadikar Padmakar V. , Ghadrian Taghi
Published: May 2005

ESR spectra of bipyridyl(Bipy) adducts of copper(II) salicylhydroxamates were obtained at room and liquid nitrogen temperatures in polycrystalline samples. The bonding ability of Bipy is discussed on the basis of N‐superhyperfine coupling (N‐Shf) while the magnitude of CuL bonding is discussed on the basis of ESR parameters. The room temperature magnetic moment values indicated tetragonal distortion. The nature of distortion is also discussed on the basis of N‐Shf coupling.
Quadrupole effects in crown ether–salt complexes: A solid‐state NMR study
Authors: Pietrass T. , Burkert P. K.
Published: May 2005

7Li, 23Na and 13C solid‐state NMR spectroscopy under static and magic angle spinning conditions was used to study the salt complexes of lithium chloride, lithium bromide, lithium perchlorate and lithium nitrate with 12‐crown‐4 and of sodium nitrate with 15‐crown‐5, Structural and dynamic features of the compounds are discussed, focusing on the quadrupolar interaction and temperature‐dependent phenomena.
Angular dependence of geminal spin–spin coupling constants in a prototype CH2 group. J(H,H) versus interbond angle in methane
Authors: Geertsen Jan , Oddershede Jens , Raynes William T.
Published: May 2005

Correlated ab initio calculations of the dependences of the proton–proton spin–spin coupling constant J(H1, H2) in methane with the variation of the H1CH2 interbond angle are reported. The other coupling constants, including J(C, H), were simultaneously calculated. The coupling constants J(H1, H2) and J(C, H1) increase nearly linearly with the opening of the interbond angle whereas J(H2, H3) and J(C, H3) decrease. J(H3, H4) is only very slightly affected. The changes are due almost solely to changes in the Fermi contact term. The angular dependence is slightly larger at the SCF level of calculation than at the correlated level. The change in the geminal coupling constant J(H1, H2) with respect to equilibrium geometry is given to within 0.025 Hz by ΔJ(H1, H2) (Hz) = 41.57 sin α12 − 8.90 sin2 α12, where α12 is the increase in the interbond angle with respect to equilibrium ( − 10° ⩽ α12 ⩽ 10°).
77Se, 13C and 1H NMR spectra of acyclic phenylselenenylalkanes and ‐alkenes and some of their selenoxides
Authors: Duddeck Helmut , Wagner Petra , Rys Barbara
Published: May 2005

The 77Se, 13C and 1H NMR spectra of 57 mostly new compounds with phenylselenenyl groups attached to acyclic alkanes, alkenes and phenylalkanes and of 10 corresponding selenoxides are reported. Substituent effects on the chemical shifts of these nuclei were determined and are discussed in terms of the conformation and configuration. The results suggest that, in contrast to PhSeCCSePh fragments, CCCSe chains prefer a gauche conformation.
19F NMR properties of some trifluorovinyl‐ and pentafluoropropenyl‐substituted aromatics
Authors: Koroniak Henryk , Palmer Keith W. , Dolbier William R. , Zhang Hua‐Qi
Published: May 2005

19F NMR chemical shifts and coupling constants are given for a series of aryl (phenyl, naphthyl and phenanthryl) substituted trifluorovinyls and (E)‐ and (Z)‐perfluoropropenyls. The relationship between the 19F NMR chemical shifts and the configurational orientation of the perfluoroalkenyl substituents is discussed.
Nitroxide radical as a probe for molecular conformation. Part I. 13C NMR study of the interaction of N,N‐dimethylamides with nitroxide radical
Authors: Wawer Iwona , Ströhl Dieter , Kleinpeter Erich
Published: May 2005

13C NMR contact shifts induced by the 2,2,6,6,‐tetramethylpiperidine nitroxide radical (TMPN) were measured for N,N‐dimethyl‐para‐substituted benzamides and N,N‐dimethyl‐β‐bromo‐ and ‐α,β‐methylacrylamides. The shifts were linear functions of radical concentration, cr. It was found that N‐methyl group anti to the carbonyl group is a better acceptor site than the syn‐N‐methyl group and that there is a relationship between Δδ/dcr and the non‐planarity of molecules of amides with an s‐skew conformation. The electrostatic potential of amide molecules obtained from MNDO calculations was used to predict the stereospecific interaction with radicals.
Configurational effects in 17O NMR chemical shifts of hydroxyl‐substituted, bicyclo [2.2.1]heptenes and ‐heptanes, their methylated derivatives and some related compounds
Authors: Kolehmainen Erkki , Laihia Katri
Published: May 2005

Well resolved natural abundance 17O NMR spectra of 27 mono‐, di‐, tri‐ and tetrahydroxybicyclo[2.2.1]heptenes and ‐heptanes (norbornenes or norbornanes), their methylated derivatives and some related compounds were measured for 0.5 M or saturated solutions in acetonitrile at 65°C. In addition, the 17O NMR chemical shifts of 14 aliphatic and alicyclic alcohols were also determined for reference purposes. The 17O NMR chemical shifts of all compounds were assigned. Both methyl‐ and hydroxyl‐induced deshielding β‐effects were consistent with those reported in the literature. Similarly, observed shielding γ‐effects were in agreement with the earlier observations and characteristic especially for mutual γ‐gauche and ‐eclipsed orientations of substituents. In addition, clear shielding δ‐effects (up to 10 ppm) were observed in tri‐ or tetrahydroxynorbornanes. These δ‐effects can be related to the attractive van der Waals interactions observed earlier in 13C NMR chemical shifts.
Non‐equivalence Magnetique en Resonance Nucleaire—IV. Influence de Plusieurs Types de Dissymetries sur les Deplacements Chimiques et les Couplages Relatifs a des Systemes OCH2CH3 et SCH2CH3
Authors: Martin Mme Maryvonne L. , Lefevre M. François , Lapeyre Mme Denise , Martin M. Gérard J. , Mantione M. Richard
Published: May 2005

La non‐équivalence magnétique des protons méthyléniques de groupements ACH2CH3 est étudiée dans plusieurs séries de composés. Les effets sont comparés d'une part dans les séries A = O et A = S, d'autre part dans les composés présentant un carbone asymétrique, un carbone de type cétal ou une dissymétrie allénique. L'influence de la substitution sur le carbone en α de AEt est discutée en relation avec les conformations. Une variation de la constante de couplage entre les protons méthyléniques géminés en function de la nature des substituants lointains est mise en évidence.
Studies in nuclear magnetic resonance—IX. Rotational barriers in substituted N,N‐dimethylbenzamides
Authors: Jackman L. M. , Kavanagh T. E. , Haddon R. C.
Published: May 2005

The barriers to rotation about the CN bond in eighteen substituted N,N‐dimethylbenzamides have been determined by complete line shape analysis of the NMR spectra of the N,N‐dimethyl protons. The barriers have been correlated with the substituent constants σ and σ+. It has been shown that polar solvents increase the barrier in N,N‐dimethylbenzamide.

Acid catalysis of rotation about the amide CN bond in N‐(p‐N,N‐dimethylcarboxamidobenzyl)‐pyridinium bromide has been investigated. 18O exchange studies show that catalysis is due to N‐protonation rather than the formation of a tetrahedral intermediate. The rate of rotation is a function of the Hammett acidity function, H0, and the water activity, and it is shown that proton exchange between the N‐ and O‐protonated species involves the intermediacy of a water molecule.

The differences in chemical shifts for the non‐equivalent N, N‐dimethyl groups of the benzamides are also a function of the substituents. Possible explanations of this phenomenon are discussed.
Electron transfer processes—X: Radical ions with hydrogen bridges derived from 1,1′,3,3′‐tetraketo‐Δ2,2′‐biindan, 5,6,11,12‐naphthacenetetrone, 1,4,9,10‐anthracenetetrone, and 1,4,5,8‐naphthalenetetrone
Authors: Russell Glen A. , Neugebauer Franz A.
Published: May 2005

Radical anions and cations have been prepared by the reduction of the title compounds or their diprotonated derivatives. The same radical ions have been observed by oxidation of the dihydro derivatives. Electron spin resonance hyperfine splitting constants have been assigned on the basis of Hückel and McLachlan calculations and selective substitutions. The hyperfine splitting by the bridging hydrogen atoms in the radical anions was much weaker (0·5 to 0·7 gauss) than for the corresponding radical cations (2 to 3 gauss) for the naphthacene, anthracene, and naphthalene dihydrotetrones. This is interpreted to be a result of orbital symmetry since, in the highest occupied MO for the anion but not for the cation, a nodal plane passes through the bridging hydrogen atom.
Substituent effects on magnetic non‐ equivalence in acetals
Authors: Rattet Lana S. , Goldstein J. H.
Published: May 2005

The proton and 13CH satellite spectra of five diethyl haloacetals have been analyzed and their spectral parameters obtained. The parameters for the ethoxy methylene protons indicate the extent of their magnetic nonequivalence. It has been found that these parameters are dependent on the degree of halogen substitution in the group Z, which is bonded to the central carbon atom, and correlate well with the corresponding group electronegativity values, a′ z, proposed by Huheey. The parallel behavior of the methylenic J(CH) and chemical shifts indicates that a primarily through‐bond mechanism is responsible for propagation of both the electronic and symmetry effects observed. Transmission factors calculated from the spectral data agree with independent estimates reasonably well, thus supporting the conclusions reached here.
Applications of proton magnetic resonance spectroscopy to structural problems—XXXIV: Partial bond fixation in bicyclic heteroaromatic compounds
Authors: Boulton A. J. , Halls P. J. , Katritzky A. R.
Published: May 2005

NMR spectral parameters are reported for benzofurazan, 1,2,3‐ and 2,1,3‐benzothiadiazole, and 1‐methyl‐ and 2‐methyl‐benzotriazole. The coupling constants are discussed in connection with the aromaticity of these compounds and the occurrence of partial bond fixation.
Etude par resonance magnetique nucleaire des interactions noyau‐substituant dans les acetanilides para‐substitues
Authors: Bennett J. , Delmas M. , Maire J. C.
Published: May 2005

Les spectres de RMN de quinze acétanilides para‐substitués XC6H4·NH·CO·CH3 (X = NH·CO·ME; NH2; CO·OEt; COOH; Cl; OEt; F; H; OMe; CH3; NO2; C6H5;NNC6H5; Me3Si) ont été étudiés. Il y a une relation linéaire entre δ et δNH et les constantes σP de Hammett. Le couplage J(o‐HH) entre les protons aromatiques est relié plutôt à σR0. La constante J (13CH) dans le groupe CH3, est indépendante de X.
The NMR spectra of some iodo‐ and bromo‐fluorobenzenes. A novel solvent effect on ortho fluorine‐fluorine couplings
Authors: Cooper M. Ashley
Published: May 2005

The NMR spectral parameters for some bromo‐ and iodo‐substituted fluorobenzenes are presented, and the derived meta‐ and para‐ fluorine‐fluorine couplings are shown to be in accord with the predictions made by Abraham et al., using an additive substituent constant scheme. While the approximation of additive substituent effects is quite good, it is shown, however, that with highly accurate experimental values there are small deviations from perfect additivity. The existence of a large solvent effect on 3JFF is demonstrated and the mechanism of this effect is discussed. It is emphasized that certain discrepancies in the literature between various values of the same 3JFF may be due to this large, hitherto unrecognized solvent dependence.
Etude de la Basicite de Composes Organophosphores Typiques dans Leurs Complexes de Lewis Avec le Trifluorure de Bore
Authors: Elegant Lucien , Azzaro Marcel , Mańkowski‐Favelier Raymonde , Mavel Gérard , Morize Nicole
Published: May 2005

On a étudié, en résonance du proton et du fluor (à température variable) ainsi qu'en résonance du bore et du phosphore, un certain nombre de complexes entre BF3 et des composés organo‐phosphorés typiques. En ce qui concerne BF3, la résonance de bore reste insensible à la force du complexe; par contre, la résonance du fluor suggéère l'existence de plusieurs types de complexes, soit sur le groupe phosphoré, soit sur les hétéroatomes (par example N, O) de la molécule. Ces complexes sont vraisemblablement de type σ pur. Le déplacement chimique des protons dans la molécule organo‐phosphorée subit sensiblement les mêmes perturbations que dans les autres molécules complexables (amines, esters, etc.); ces perturbations peuvent provenir avant tout d'effets d'anisotropie magnétiques; par contre, les couplages proton‐phophore suivent la modification de l'électronégativité de ce dernier.
Interactions Intramoleculaires—X: Etude par RMN des Équilibres Conformationnels de Cyclohexènes Monosubstitutés en 4 et du Dicyano‐1,2 Cyclohexane trans
Authors: Aycard Jean‐Pierre , Bodot Hubert , Garnier Roger , Lauricella Robert , Pouzard Guy
Published: May 2005

Les enthalpies libres conformationnelles des substituants CN, Cl et COOC2H5 ont été évaluées à partir de l'étude des spectres RMN des cyclohexènes (D4‐3,3,6,6) monosubstitués en 4.

Les spectres RMN du dicyano‐1,2cyclohexane (D4‐3,3,6,6)trans ont permis une estimation de l'équilibre conformationnel (dans différents solvants) ainsi que de l'énergie d'interaction gauche diéquatoriale entre les deux groupements CN.
Substituentenabhängigkeit der Ringinversion des Ungesättigten Siebenringes bei Benzocycloheptenderivaten. Konformative Beweglichkeit flexibler Ringsysteme—XIV: Untersuchungen mit Hilfe der Protonenresonanzspektroskopie
Authors: Kabuß S. , Schmid H. G. , Friebolin H. , Faißt W.
Published: May 2005

Bei insgesamt 20 Benzocycloheptenderivaten mit 1, 2 und 3 Paaren geminaler Substituenten wurden die konformativen Umwandlungen des ungesättigten Siebenringes PR‐spektroskopisch untersucht.

Bei allen Verbindungen ist das Umklappen des Ringes bei − 80°C ‘eingefroren.’ In nachweisbarer Menge liegt bei dieser Temperatur in allen Fällen nur ein Konformeres vor, vermutlich dasjenige mit der Sesselform des Siebenringes.

Die Werte der freien Aktivierungsenthalpie ΔG≠ der Sesselinversion liegen zwischen 9,9 und 13,7 kcal/Mol. Bei di‐ und tetrasubstituierten Benzocycloheptenen hängt der ΔG≠‐Wert von der Stellung der Liganden ab: Bei den disubstituierten Derivaten ist ΔG≠ am größten bei 5‐ Stellung und am kleinsten bei 3‐ Stellung der Substituenten. Bei den tetrasubstituierten Derivaten ist das Umklappen des Ringes im Verhältnis zu den vergleichbaren Dimethylverbindungen erschwert, wenn die Ligandenpaare in 3,6‐ oder 3,7‐ Stellung stehen, jedoch erleichtert, wenn sie in 3,5‐ oder 4,6‐ Stellung angeordnet sind. Der bei 3,5‐ bzw. 4,6‐ Stellung der Ligandenpaare beobachtete Effekt wird auf die transanulare Abstoßung synaxialer Substituenten zurückgeführt, durch die der Cycloheptensessel abgeflacht wird. Eine solche Abstoßung fehlt bei 3,6‐Stellung der Liganden. Bei den Verbindungen mit 3,7‐ständigen Liganden führt die trans‐anulare Abstoßung hingegen zu stärkerer Wellung (puckering) des Sessels; das Umklappen könnte dadurch erschwert sein.

Für Benzocyclohepten wurden die für die gegenseitige Umwandlung von Sessel‐, Wannen‐ und Twist‐Konformeren (S, W und T) erforderlichen Werte der Aktivierungsenergie durch Modellrechnungen ermittelt. Günstigster Weg für das Umklappen des Sessels ist der Versionsweg S→W über die Übeergangskonformationen V56. Die hierfür berechnete Aktivierungsenergie (14,6 kcal/Mol) stimmt mit der experimentell ermittelten (13 ± 1,5 kcal/Mol) gut überein. Für die Aktivierungsenergie der Pseudorotation W → T wurde mit 11,1 kcal/Mol ein nur wenig neidrigerer Wert berechnet.
The NMR spectra of some 3‐coordinate phosphorus compounds containing chloromethyl and isopropyl groups
Authors: Bissey J. E. , Goldwhite H. , Rowsell D. G.
Published: May 2005

Analysis of the proton NMR spectra of Pr1PCINMe2 indicates magnetic non‐equivalence of the methyl groups due to the adjacent asymmetric phosphorus atom. High temperatures, or the addition of chloride ion, induce an exchange reaction with inversion of configuration at phosphorus. The corresponding fluoride is configurationally stable at high temperatures. The compounds CICH2PXNR2 (X = Cl, F; R = Me, Et) have non‐equivalent protons in the chloromethyl group. The two HCP coupling constants in the chlorides of this series are of opposite sign, whereas in the fluorides they are of the same sign.
PMR investigation of organic cations—I: Trithienyl methyl carbonium ions
Authors: Taddei F. , Spagnolo P. , Tiecco M.
Published: May 2005

PMR spectral parameters are reported for the isomeric trithienyl carbonium ions. The low field shifts, relative to the corresponding carbinols, are discussed in relation to the delocalization of the positive charge into the thiophene ring bonded in position 2 or 3. A linear correlation is found between chemical shifts and π‐charge densities and the proportionality constant is higher than that previously found for benzene derivatives. Vicinal coupling constants in these systems are satisfactorily in agreement with the corresponding calculated π‐bond order.
Variable temperature magnetic resonance spectra of 1‐fluorocyclooctene
Authors: Weigert Frank J. , Strobach Donald R.
Published: May 2005

Variable temperature fluorine magnetic resonance spectra have been obtained for 1‐fluorocyclooctene. At low temperatures both the processes of ring inversion and pseudorotation are slow on the NMR time scale, and two distinguishable conformations can be observed with a free energy difference of 95 cal/mole and a fluorine chemical shift difference of 6·7 ppm. A process with a free energy of activation of 6·1 kcal/mole interconverts the two conformations.
Kernresonanzuntersuchungen am 1.10‐Phenanthrolin und seinen Komplexverbindungen—IV: 13C‐Resonanzen des freien und protonierten 1.10‐Phenanthrolins
Authors: Rosenberger H. , Pettig M. , Madeja K. , Pehk T. , Lippmaa E.
Published: May 2005

Die chemischen Verschiebungen der 13C‐Resonanzen für freies und protoniertes 1.10‐Phenanthrolin werden bestimmt und mit Hilfe der in Teil I1 und Teil III2 beschriebenen π‐ und (σ + π)‐MO‐Elektronenrechnungen interpretiert.

Bei der Protonierung ist die Verschiebung der 13C‐Signale der dem Stickstoff benachbarten C‐Atome zu höherem Feld charakteristisch; dieser Effekt wird mit einer Verringerung der N–C‐Überlappungsbesetzung gedeutet. Für das mono‐ und diprotonierte 1.10‐Phenanthrolin wird eine relativ geringe formale Ladung am Stickstoff festegestellt (Δ = 0,0 bis 0,3).
Nuclear magnetic resonance spectra and structure of some alkyl vinyl sulphides
Authors: Ceccarelli G. , Chiellini E.
Published: May 2005

The NMR spectra of eight alkyl vinyl sulphides have been analyzed and the parameters compared with those obtained from an analogous series of oxygen derivatives. It is shown that a definite parallelism exists between chemical shifts and HH coupling. Difference in absolute values have been explained by mesomeric interaction magnified image involving the ability of sulphur to accommodate a decet of electrons in its valence shell. By analogy with alkyl vinyl ethers, it is possible to predict a similar correlation between the spectral characteristics and relative reactivity of vinyl sulphides in cationic polymerization.
NMR‐untersuchungen an cyclohexanen: 220 MHz‐messungen an di‐ und trisubstituierten cyclohexanen
Authors: Naegele Walter , Wendisch Detlef
Published: May 2005

Im Zuge der Konfigurations‐ und Konformationsuntersuchungen an substituierten Cyclohexanen wurden 220 MHz‐Spektren von di‐ und trisubstituierten Verbindungen gemessen. In vielen Fällen gestattet die höhere Frequenz eine weitgehende Zuordnung aller Ringprotonen. Spezielle Eigenheiten der Spektren werden diskutiert.
A detailed evaluation of the dependence of 3J(HH) on bond angle in alkenes and cycloalkenes
Authors: Cooper M. Ashley , Manatt Stanley L.
Published: May 2005

Newly determined and accurate data for the magnitudes of cis vinyl proton‐proton spin‐spin coupling constants in cis‐dialkylethylenes and cycloalkenes have been obtained. With these new data and also values taken from the recent literature, it has proved possible to make a critical determination of the correlation between 3J(HH) and CCH bond angles in ethylenic systems. It is suggested that it is possible to obtain accurate estimates of bond angles using NMR coupling constants, even though much more data will be required to fully substantiate this proposal. Whereas cis‐3J(HH) decreases rapidly with increasing CCH bond angles, evidence is presented that the opposite is the case for trans‐3J(HH). A brief theoretical discussion of these trends in coupling constants is given.
Die Konformativen Umwandlungen des Ungesättigten Siebenringes in 4.5.6‐Trithia‐1.2‐Benzocycloheptenen‐(1) Konformative Beweglichkeit Flexibler Ringsysteme—XVI. Untersuchungen mit Hilfe Der Protonenresonanzspektroskopie
Authors: Bredow K. V. , Jaeschke A. , Schmid H. G. , Friebolin H. , Kabuß S.
Published: May 2005

Die Konformerengleichgewichte und die konformativen Umwandlungsprozesse des 4.5.6‐Trithia‐1,2‐benzocycloheptens‐(1) (1) sowie seiner 3′.6′‐Dimethoxy‐, 3′.6′‐Dimethyl‐ und 3′.6′‐Diphenyl‐ derivate (2, 3 und 4) wurden PR‐spektroskopisch untersucht. Die Lösungen dieser Substanzen sind Gleichgewichtsgemische zweier Konformerer, von denen das eine vermutlich Sesselform, das andere Wannenform hat. Der Wert der freien Konformationsenthalpie ΔGw des Wannenkonformeren ist abhängig von der Größe der Substituenten R in 3′‐ und 6′‐Stellung. ΔGw beträgt für R = H 1,03 kcal/Mol, R = OCH3 0,82 kcal/Mol, R = C6H5 0,50 kcal/Mol und R = CH3 −0,19 kcal/Mol. Durch Kristallisation bei +60° kann im Falle der substituierten Trithiabenzocycloheptene jeweils ein reines Konformeres in kristalliner Form erhalten werden. Beim Dimethoxyderivat kristallisiert das Sesselkonformere, beim Dimethyl‐ und dem Diphenylderivat das Wannenkonformere aus. Nach Auflösen der Kristalle erfolgt Einstellung des Konformerengleichgewichts; bei 0°C betragen die Halbwertszeiten 2 bis 15 Minuten. Anhand der Temperaturabhängigkeit der Protonenresonanzen kann experimentell zwischen zwei verschiedenen konformativen Umwandlungsprozessen unterschieden werden: Der langsamere Prozess wird der Version, der schnellere der Pseudorotation des Siebenringes zugeordnet. Die freie Aktivierungsenthalpie ΔGv≠ der Version wurde im Falle des 4.5.6‐Trithia‐1.2‐benzocycloheptens‐(1) nach der ‘line‐shape’‐Methode, im Falle des Diphenylderivates nach der ‘Äquilibrierungs’‐Methode bestimmt. Die beiden anderen Verbindungen wurden mit beiden Methoden untersucht. Die mit den verschiedenen Methoden bestimmten ΔGv≠‐Werte stimmen gut überein. Die freie Aktivierungsenthalpie der Version ΔGv≠ unmd diejenige der Pseudorotation ΔGP≠‐Werte ≤ 11,4 kcal/Mol.
Proton resonance spectra of heterocycles—VII: Proton NMR spectra of 2‐methyl‐benzoxazoles,‐benzothiazoles and ‐benzoselenazoles
Authors: Katritzky A. R. , Takeuchi Yoshito
Published: May 2005

Chemical shifts and coupling constants are reported for a series of the title compounds and the effects of substituents on these values correlated with the corresponding effects in benzenes. Partial bond fixation in these and other benzo‐heterocycles is discussed together with the general prediction of NMR parameters in substituted heterocycles.
NMR study of 4‐deoxy‐α‐L‐threo‐4‐enohexopyranosyluronic acid (1 → 3)2‐acetamido‐2‐deoxy‐D‐hexoses produced in the enzymic digestion of hyaluronate, chondroitin and chondroitin sulfates
Authors: Hirano Shigehiro
Published: May 2005

The conformation of 4‐deoxy‐α‐L‐threo‐4‐enohexopyranosyluronic acid (1 → 3)2‐acetamido‐2‐deoxy‐d‐hexoses was analyzed by NMR spectroscopy. The half‐chair (H12) conformation was found in the unsaturated uronide moiety and the chair (Cl) conformation in the hexosamine moiety.
Multiple NMR analysis of the affinin
Authors: Correa J. , Roquet S. , Díaz E.
Published: May 2005

The configuration of the insecticidal and medicinal lipid ‘affinin,’ N‐isobutyldeca‐trans‐2, cis‐6, trans‐8‐trienamide, may be assigned in an unequivocal manner by NMR spectroscopy. The spectral data and the advantages of the multiple irradiation methods are presented and discussed.
The NMR spectra of some 1,3‐oxathians and the influence of heteroatoms on the coupling constants of adjacent protons
Authors: Allingham Y. , Crabb T. A. , Newton R. F.
Published: May 2005

The preparation of 4‐phenyl‐1, 3‐oxathian, 6‐methyl‐1, 3‐oxathian, and some of their 2‐substituted derivatives is described. Significant features of their NMR spectra are discussed with particular reference to the influence of the heteroatoms on the coupling constants of adjacent protons.
A systematic approach to the AA′BB′, AA′BB′MX and derived systems in nuclear magnetic resonance
Authors: Batterham T. J. , Bramley R.
Published: May 2005

The AA′BB′ and AA′BB′MX nuclear magnetic resonance spin systems for I = ½ nuclei have been analysed. Expressions for the transition frequencies and intensities have been obtained which have the maximum accuracy consistent with practicable use. The analyses have been applied respectively to a hypothetical AA′BB′ nuclear spin system and to the two molecules para‐ fluoro‐phenyldichlorophosphine and tris‐para‐fluorophenylphosphine. Inconsistencies in earlier treatments of the AA′BB′ system have been clarified.
Nuclear magnetic resonance spectroscopy. Analysis of the 1H and 13C spectra of Br13CH213CH2Br
Authors: Carhart Raymond E. , Roberts John D.
Published: May 2005

The 1H and 13C NMR spectra of 1,2‐dibromoethane‐13C2 have been analyzed to determine the magnitude (38·9 Hz) and sign (positive) of 1J(CC) relative to those of 3J(HH) (positive). This type of coupling appears to be rather insensitive to the presence of bromine or methyl as substituents on the carbons.
A line width method for determining chemical exchange rates from NMR spectra
Authors: Ramey Kermit C. , Louick David J. , Whitehurst Philip W. , Wise William B. , Mukherjee Rabindranath , Moriarty Robert M.
Published: May 2005

The applicability of W½, the line‐width at one‐half height corrected for field inhomogeneity and couplings, for characterization of nuclear magnetic resonance line shapes generated by exchange averaging of chemical shifts has been investigated for the case PA= PB. The Gutowsky‐Holm equation, simplified by the assumption of a large T2º such that T= 0, was used to produce a family of curves relating W½corrected to the rate of exchange for various ΔvABvalues.

The rate of internal rotation about the CN amide bond has been studied in neatN,N‐dimethyl‐formamide between 79·5 and 159° by the W½method and the results, Ea= 24·9 and 24·1 Kcal/mole at 60 and 100 MHz do not agree with those recently reported by Rabinovitz and Pines, Ea= 20·5 Kcal/mole obtained by the total line shape method. For neatN,N‐dimethylacetamide and for solutions of DMA in dimethylsulfoxide‐d6, application of the W½method yielded Ea, ΔH‡ and ΔS‡ values which are in excellent agreement with those obtained by Neuman and Jonas for DMA‐dεusing a total line shape analysis. The thermodynamic parameters for neatN,N‐dimethylcarbamoyl chloride obtained by the total line shape and W½methods are also in excellent agreement, 16·4 and 16·8 Kcal/mole for Eaand 15·8 and 16·2 Kcal/mole for ΔH‡, respectively.

The W½method was also used for the determination of the activation parameters for rotation about the carbon‐nitrogen bond in the following thioamides:N,N‐dimethylthiobenzamide, (Ea= 19.8 Kcal/mole),N,N‐diethylthiobenzamide, (Ea= 20·4 Kcal/mole),N,N‐dimethylphenylthio‐acetamide (Ea= 21·4 Kcal/mole). The results obtained for these thioamides are compared with the corresponding amides. SpecificallyN,N‐dimethylbenzamide andN,N‐diethylbenzamide were studied using the W½method and activation energies for rotation about the carbon‐nitrogen bond of 17·5 and 15·6 Kcal/mole, respectively, were found. The relative magnitudes of these parameters are discussed on the basis of molecular geometry of the thioamides. Attention is drawn to the fact that for structurally related amides and thioamides, the barrier heights for internal rotation are not greatly different.