bluuebunny/crossref_metadata_2025 huggingface dataset:
Pitting corrosion behavior of superferritic stainless steel in waters containing chloride
Authors: Moretti G. , Quartarone G. , Tassan A. , Zingales A.
Published: May 2005

On a cost‐performance basis, superferritic stainless steel (SFSS) grades can now be considered competitive choices for brackish and sea water cooling systems. The pitting corrosion of a SFSS (X2CrNiMoTi 25 3.6 3.5) was tested in a chloride/sulfate solution similar to sea water, as a function of temperature, pH, and salinity. Potentiodynamic polarization techniques and experimental stability diagrams were used to evaluate the pitting conditions. The critical pitting temperature (CPT) was found to be above 50°C, and the re‐passivation tendency under critical temperatures was satisfactory even when the pH was less than the depassivation pH, a condition which simulates a propagating occluded cell. The SFSS behavior in the presence of chlorine was evaluated by means of potentiodynamic tests and by studying the cathodic reduction kinetics of Cl2and O2(air).
Corrosion and passivity of Hastelloy C4 in a high salinity brine
Authors: Thies A. , Schultze J. W.
Published: May 2005

Corrosion and passivity of Hastelloy C4 in Q‐brine, a magnesium chloride rich brine of pH 4.5 at room temperature, was studied by potentiodynamic (i(U) and C(U)) or potentiostatic polarisation. While the alloy rests passive at room temperature, no coherent, protecting passive layer is formed at temperatures above 60°C and potentials exceeding 0.2 V SHE. XPS analysis shows that at the rest potential and temperatures below 110°C, the oxide layer is about 1 nm thick and composed of chromium and molybdenum oxides without incorporation of Mg2+or Cl−from the electrolyte. At 200°C, its thickness increases 20 nm after 4 days and Mg+inclusions are found. Across the weld, Scanning Reference Electrode measurements in dilute NaCl showed a homogeneous potential distribution indicating that bulk material, heat affected zone and weld have the same electrochemical properties.
PH‐Abhängigkeit der korrosionsinhibierenden bzw. ‐stimulierenden Wirkung von Polyacrylsäuren auf Aluminiumpigmente
Authors: Müller B. , Dawidowski U.
Published: May 2005

Der isoelektrische Punkt (IEP: pH ≈ 9) von Aluminiumoxid ist von entscheidender Bedeutung für die korrosionsinhibierende Wirkung von Polyacrylsäuren in Bezug auf Aluminiumpigmente im alkalisch wäßrigen Medium:

Oberhalb des IEP (pH 10):

Hoch‐ und niedrigmolekulare Polyacrylsäuren inhibieren die Korrosion, wobei deren Wirkung mit zunehmender Molmasse abnimmt.

Unterhalb des IEP (pH 8):

Niedrigmolekulare Polyacrylsäuren inhibieren die Korrosion, aber weniger effektiv als bei pH 10; die korrosionsinhibierende Wirkung nimmt mit zunehmender Molmasse ab.

Hochmolekulare Polyacrylsäuren stimulieren die Korrosion; d. h. am IEP findet eine Wirkungsumkehr statt.
In Situ Polymerization of Hybrid Polyethylene‐Alumina Nanocomposites
Authors: Zhang Xi , Simon Leonardo C.
Published: May 2005

Summary: Polyethylene‐alumina nanocomposites were prepared using in situ polymerization. Alumina nanomers were prepared by treating alumina nanoparticles with an alkylaluminium compound and a vinyl alcohol. This approach led to (a) grafting double bonds onto the alumina surface, and (b) dispersion of alumina nanoparticles in toluene minimizing aggregation. The level of dispersion of nanomers was a function of the molar ratio between the alkylaluminium compound and the vinyl alcohol. Copolymerization of ethylene and nanomers catalyzed by the coordination catalyst (diimine)NiCl2/MAO produced hybrid nanocomposites with polyethylene chains covalently bonded to the surface of alumina nanoparticles. Using excess of vinyl alcohol produced crosslinked material. Appropriate preparation of nanomers has produced a good dispersion of alumina nanoparticles in the polyethylene matrix. At certain compositions the final material had better mechanical properties, such as yield strength and toughness, than the homopolyethylene.

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Pressure, the Critical Factor Governing Final Microstructures of Cured Rubber/Clay Nanocomposites
Authors: Liang Yu‐Rong , Lu Yong‐Lai , Wu You‐Ping , Ma Yong , Zhang Li‐Qun
Published: May 2005

Summary: The changes in both local intercalated structures and spatial distribution states of organoclays (OC) in rubber/clay nanocomposites (RCNs) caused by vulcanization were monitored by using WAXD and TEM, and the corresponding mechanism was studied. It was first discovered that the pressure was the critical factor determining the final microstructures of cured RCNs. The cured RCNs with fine dispersion could be obtained through vulcanization under atmospheric pressure.

TEM images of SBR/clay nanocomposites cured at 15 MPa pressure (left) and atmospheric pressure (right).

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TEM images of SBR/clay nanocomposites cured at 15 MPa pressure (left) and atmospheric pressure (right).
Glasfasern—Herstellung—Erzeugnisse
Authors: Hansmann Joseph
Published: May 2005

Die eingeführten Werkstoffbezeichnungen und Definitionen sind der Beschreibung der Glasfasererzeugnisse und ihrer Herstellungs‐verfahren vorangestellt. Die verschiedenen ‐ den einzelnen Erzeugnisgruppen angepaßten ‐ Ausrüstungen sind nicht nur Verarbeitungshilfsmittel, sondern entscheiden über die Einsatzmöglichkeiten. Für die Vielfalt der Anwendungsgebiete spricht die steigende Weltproduktion von 470 000 t im Jahre 1970. Einige wirtschaftlich und technisch interessante Anwendungen werden beschrieben. Vom Straßenbau bis zum Raumanzug, von der Wärme‐und Schalldämmung bis zur Glasfaseroptik streuen die Möglichkeiten. Sind die Glasfaser‐Dämmung und ‐Isolierung noch weithin bekannt, so ist der Einsatz von über 100 Mill m2 Glasvlies im Dach‐und Dichtungsbahnsektor oder von 8 Mill. m2 Dekostoff in Westeuropa (1970) ebenso weithin unbekannt. Drainage, Heißmetallpressen, Luftfilter, Putzarmierung, Akkuscheider, Rohrleitungs‐und Bootsbau, Autoreifen und Fußbodenbelag demonstrieren die Vielfalt der Anwendungen.
Haftung und Grenzflächenreaktionen im Verbundsystem α‐Al2O3/Ni
Authors: Grünling H. W. , Hennicke H. W.
Published: May 2005

An Verbundwerkstoffmodellen aus zylindrischen Saphirstäben mit aufgesintertem Nickelring wird der Einfluß geringer Mengen von Titan oder Zirkon als Legierungsbestandteil im Nickel auf die Haftung und Verträglichkeit zwischen den Partnern unter‐sucht. Mit unlegiertem Nickel werden zeitlich und thermisch stabile Scherfestigkeitswerte zwischen 50 und 70 N/mm2 erzielt. Enthält das Nickel 0,05 At‐% Titan oder Zirkon, steigt bei günstigen Sinterbedingungen (z. B. 1300°C, 1 h) die Scherfestigkeit auf 250–280 N/mm2 an. Dieser Anstieg ist auf eine, Verbesserung der Haftung zwischen den Partnern zurückzuführen, die sich mit der Ausbildung chemischer Haftkräfte als Folge von Reaktionen zwischen der Saphiroberfläche und den im Nickel enthaltenen aktiven Legierungselementen Titan oder Zirkon erklären lassen. Bei längeren Haltezeiten, höheren Sintertemperaturen und/oder höheren Aktivmetallkonzentrationen führen diese Reaktionen zur Aufrauhung des Saphir und zur Ausscheidung von Oxidphasen der im Nickel enthaltenen aktiven Elemente in der Grenzfläche oder in einer grenzflächennahen Zone des Nickels. Diese reaktionsbedingten Grenzflächenveränderungen bewirken eine Änderung des Scherverhaltens, die sich in einer Verringerung der Scherfestigkeit äußern kann. Die an solchen Proben gemessenen Scherfestigkeitswerte lassen keine Rückschlüsse auf die tatsächliche Haftung zwischen den Partnern mehr zu.
Nichtmetallische Hochtemperaturwerkstoffe
Authors: Petzow Günter , Buresch Friedrich Erich
Published: May 2005

Einige Sonderkeramiken kommen als Werkstoffe für Temperaturbeanspruchungen oberhalb von 1100°C in Betracht. Sie verfügen über ausreichende Warmfestigkeiten und gute Korrosionseigenschaften und mit einigen Einschränkungen auch über einen brauchbaren Thermoschock‐ und Schlagwiderstand. Im Vergleich zu den Metallen ist diese interessante Materialklasse noch sehr entwicklungsfähig.
Durch veränderliche Betriebslasten in Kerben erzeugte Eigenspannungen und ihre Bedeutung für die Anwendbarkeit der linearen Schadensakkumulations‐Hypothese
Authors: Schütz D. , Gassner E.
Published: May 2005

Die lineare Schadensakkumulations‐Hypothese liefert häufig sehr ungenaue Schätzwerte der Lebensdauer. Um zu einer Klärung beizutragen, wurden an gelochten Stäben, Formzahlak= 2,5, aus den Leichtmetallegierungen AlCuMg 2 und AlZnMgCuAg im Kerbgrund während des ersten von Makrorissen freien Lebensdauerabschnittes die Eigenspannungen gemessen und darauf aufbauend eine bezüglich der Eigenspannungen korrigierte Hypothese angewendet.
Ermüdungsverhalten von SiSiC
Authors: Richter H. , Willmann G. , Heider W.
Published: May 2005

Auf der Basis der Theorie der linear‐elastischen Bruchmechanik wird die für die Konstruktion benötigte, zeitabhängige mechanische Festigkeit (Ermüdung) von stranggepreßtem und schlickergegossenem Siliziumcarbid (SiSiC) bei Raumtemperatur bestimmt.

Der Zusammenhang zwischen Belastungshöhe, Ausfallswahrscheinlichkeit und Zeit wird in Form von SPT‐Diagrammen dargestellt.
Quasistatisches Verformungsverhalten reiner Sintereisen im Temperaturbereich von –184 bis 600°C
Authors: Klumpp S. , Palma E. S. , Vöhringer O. , Macherauch E.
Published: May 2005

Reine Sintereisenwerkstoffe mit Dichten zwischen 6,88 und 7,57 g/cm3 wurden im Temperaturbereich von –184 bis 600°C quasistatisch zugverformt. Ergänzende Druckverformungen erfolgten bei 20°C. Anwachsende Dichte bewirkt ansteigende Werkstoffwiderstands‐ und Duktilitätskenngrößen aufgrund zunehmender tragender Probenquerschnitte, geringerer Porenzahl, runderer Poren mit geringerer Kerbwirkung sowie einer geringeren Zahl der von Poren ausgehenden Rissen. Bei Druckverformung entstehen nach gleichen Deformationen groößere Fließspannungen als bei Zugverformung, da Porenschließeffekte und die Behinderung von Rißbildungen die tragenden Probenquerschnitte vergrößern. Das Verformungsverhalten wird bei tiefen Temperaturen durch thermisch aktivierte Prozesse mit kurzreichenden Wechselwirkungen von Versetzungen mit Gleithindernissen, bei mittleren Temperaturen durch dynamische Reckalterungsvorgänge aufgrund von elastischen Wechselwirkungen bewegter Versetzungen mit diffundierenden Kohlenstoffatomen und bei hohen Temperaturen durch erholungskontrollierte Versetzungskriechprozesse bestimmt.
Fluid phase equilibria in supercritical fluid chromatography with CO2‐based mixed mobile phases: A review
Authors: Page Steven H. , Sumpter Sheldon R. , Lee Milton L.
Published: May 2005

In supercritical fluid chromatography (SFC), cosolvents (modifiers) have been added to CO2 in order to deactivate the analytical column and to improve the solvating power of CO2 for extending the utility of SFC to polar and high molecular weight solutes. However, the use of modifiers has proven to be difficult, and irreproducibility in retention and selectivity is often observed.

This comprehensive review focuses on the phase behavior of analytically useful CO2‐based mixed mobile phases in SFC. All of the CO2‐based mixed mobile phases which have been used in packed or open tubular column SFC are reviewed. All of the available fluid phase equilibria data for such binary fluids are discussed, and the P‐T‐x region which is applicable to SFC is compiled in both graphs and tables. Single phase regions (pressure and temperature) are listed by mol% modifier. However, only mixtures of CO2 + benzene, + ethanol, + hexane, + methanol, or + toluene have enough P‐T‐x data points to enable extrapolation to any other conditions used in conventional SFC (0–20 mol% modifier, 40–400 atm, and 0–200°C). Problems associated with estimating the critical parameters of the pure components or the mixtures are reviewed. Phase transitions in the syringe pump, transfer lines, injector, column, and restrictor are delineated. Equilibration problems associated with the preparation of mixed mobile phases (premixed cylinders, liquid or gas phase saturation, and dual pumps with on‐column mixing) and phase transitions during the operation of SFC instrumentation are discussed. Finally, future research needs are outlined.
Evaluation of surface‐bonded polyethylene glycol and polyethylene imine in capillary electrophoresis
Authors: Huang Mingxian , Vorkink William P. , Lee Milton L.
Published: May 2005

A procedure for bonding polyethylene glycol (PEG) and polyethylene imine (PEI) onto the capillary surface through a highly crosslinked polysiloxane layer containing epoxy groups has been developed. Systematic variation of the coatings can be used to (a) allow separations over a pH range of 3 to 9, (b) provide for adjustment of electro‐osmotic flow, and (c) reduce the adsorption of peptides and proteins. The variation of electroosmotic flow on these coated columns at different operational conditions can be explained using electrical double layer theory. Separations of substituted aromatic compounds and peptides on these coated columns were much improved over similar separations on untreated columns. The results indicate that PEI coated columns are suitable for the separation of basic proteins and PEG coated columns are suitable for acidic proteins. Separations of simple oligonucleotides which differ by only one base were also achieved.
Configurational and conformational analysis of norbornane‐and norbornene‐fused 4,1‐oxazepinones
Authors: Sohár P. , Stájer G. , Bernáth G.
Published: May 2005

The preferred conformations and, for the 3‐methyl‐substituted analogues also the configurations of the C‐3 atom, for 3‐unsubstituted and 3‐methyl‐substituted di‐exo‐ and di‐endo‐annellated oxazepinone derivatives fused with a norbornane or norbornene skeleton were determined by 1H and 13C NMR spectroscopy, including the use of DNOE measurements.
Application of the conformational transmission effect for the assignment of diastereotopic proton resonances
Authors: van Genderen Marcel H. P. , Buck Henk M.
Published: May 2005

A new method is presented for the assignment of the NMR resonances of the diastereotopic protons in tetrahydrofur‐furyl and pyrrolidinylmethyl groups, based on the conformational transmission effect This effect describes the conformational changes produced by an increase of coordination from four to five of a phosphorus, silicon or germanium atom attached to the tetrahydrofurfuryl or pyrrolidinylmethyl moieties. The 1H NMR conformational analysis of these cyclic four‐ and five‐coordinated compounds yields two possible results, based on two assignments of the diastereotopic proton resonances. Comparison with the conformations of the analogous four‐ and five‐coordinated systems with acyclic 2‐methoxyethyl and dimethylaminoethyl groups (which lack diastereotopic protons) directly shows which assignment is correct, since a similar conformational transmission occurs in both the cyclic and the acyclic compounds.
Long‐range tin‐tin coupling constants. III‐Four‐ and five‐bond coupling via carbon
Authors: Mitchell T. N. , Nettelbeck C.
Published: May 2005

Multinuclear NMR data (1 H, 13 C, 119 Sn) have been obtained for almost all possible isomers of the composition Me3Sn(C3Hm)SnMe3 (m = 2, 4, 6) and Me3Sn(C4Hn)SnMe3 (n = 0, 2, 4, 6, 8). The coupling constants xJ(Sn, Sn) (x = 4, 5) are not linearly related to the corresponding coupling constants xJ(H, H), but are particularly large when tin‐carbon bonds can interact hyperconjugatively with carbon‐carbon double or triple bonds.
Monitoring electrochemical reactions by 13C NMR spectroscopy
Authors: Albert Klaus , Dreher Eberhard‐Ludwig , Straub Hermann , Rieker Anton
Published: May 2005

The anodic conversion of 2,4,6‐tri‐tert‐butylphenol in methanol, leading to 2,4,6‐tris(1,1‐dimethylethyl)‐4‐methoxy‐2,5‐cyclohexadien‐1‐one, has been followed by two types of 13C NMR experiments: (a) a static procedure, inserting the electrodes directly into a rotating NMR tube and (b) a continuous flow procedure, combining electrochemical and NMR flow cells. During electrolysis the resolution of the 13C NMR spectra decreased in the static procedure owing to magnetic field gradients. In the flow procedure the resolution was comparable with that of routine spectra.
1H and 13C NMR spectra of the opioid analgesics metazocine, pentazocine and cyclazocine
Authors: Grassi Antonio , Pappalardo Giuseppe C. , Perly Bruno
Published: May 2005

The high‐frequency 1 and 13C NMR spectra (at 500 and 75.47 MHz, respectively) of metazocine (MTZ) fumarate, pentazocine (PTZ) and cyclazocine (CLZ) hydrochlorides in 2H2O solution were recorded and analysed with the aid of both homonuclear 1H1H and heteronuclear 13C1H chemical shift correlation experiments. At neutral pH all compounds were found to be configurationally heterogeneous, with the N‐equatorial isomer more populated than the N‐axial isomer (ratio ca 80:20). The low‐intensity peaks of the superimposed spectral pattern of the less populated isomer were also assigned on correlative grounds in both the 1H and 13C NMR spectra of MTZ, PTZ and CLZ. The occurrence of distinct spectra for the two configurational isomers was diagnostic of a ‘slow’ exchange process on the NMR time‐scale at the field frequencies employed for the experiments, thus suggesting a high‐energy barrier to interconversion. The experimental proton–proton coupling constants measured for the N‐equatorial form of MTZ, PTZ and CLZ were consistent with a chair conformation of the piperdinic ring in all compounds. The distinct relative agonist–antagonist potencies of the drugs investigated could therefore not be correlated with the above‐described configurational and conformational features.
Carbon‐13 NMR spectra of cyclohexaneaminonitriles
Authors: Manoharan Muthiah , Eliel Ernest L.
Published: May 2005

The 13C NMR spectra of nine 1‐(N‐piperidino) cyclohexanenitriles and of 1‐dimethylaminocyclohexanenitrile have been recorded and assigned.
195Pt and1H NMR studies of platinum(II) complexes with ethylenediamine derivatives
Authors: Rochon F. D. , Morneau André
Published: May 2005

Complexes of the types Pt(L)Cl2, [Pt(L)(D2O)2](NO3)2, [Pt(L)(D2O)(NO3)](NO3), Pt(L)(OD)2, [Pt(L)(D2O)Cl]+and Pt(L)(OD)Cl, where L = ethylenediamine,N,N‐dimethylethylenediamine,N,N′‐dimethylethylenediamine andN,N,N′,N′‐tetramethylethylenediamine, were characterized mainly by195Pt and1H (high‐ and low‐field) nuclear magnetic resonance. The NMR spectra were measured in D2O. The dichloro complexes showed a195Pt resonance between −2355 and −2433 ppm (relative to Na2PtCl6) whereas the diaqua compounds absorbed at lower field from −1821 to −1977 ppm. The signals of the monoaqua‐monochloro species were observed at intermediate field between −2030 and −2173 ppm. The dihydroxo complexes showed a resonance at lower field (about 100 ppm) than the diaqua compounds, whereas the monochloro‐monohydroxo species absorbed at about 50 ppm from the monoaqua‐monochloro species. The monoaqua‐mononitrato compounds with only two ligands absorbed at about −20 ppm from the diaqua species. The high‐field proton NMR spectra of the complexes were also measured. The195Pt–1H coupling constants were obtained from the low‐field proton NMR spectra.
Investigations utilizing the 18O isotope shift in 13C nuclear magnetic resonance spectroscopy. 1. Correlation with 17O NMR chemical shifts
Authors: Risley John M.
Published: May 2005

A survey of the one‐bond upfield 18O isotope effects on 13C NMR chemical shifts shows that a linear relationship exists between the magnitude of the isotope shift and the 17O NMR chemical shift for the corresponding oxygen atom in the molecule. The relationship holds over the entire range of functional groups to a significance level of >99.999% for 66 pairs of data points. This relationship permits an estimation with confidence of the general magnitude of an 18O isotope shift in 13C NMR, simply from a knowledge of the 17O NMR chemical shift for an oxygen atom of interest. Extrapolation of this relationship anticipates observation of downfield isotope shifts and may assist in an explanation of this rare and unusual phenomenon in NMR spectroscopy.
Conjugation of spirocyclopropane with the carbonyl group. Conformational analysis of spiro [cyclopropane‐1,2′‐steroids]
Authors: Desai Umesh R. , Trivedi Girish K.
Published: May 2005

The conjugative ability of a spirocyclopropane on 4‐en‐3‐one steroids was studied with the help of 13C NMR and two‐dimensional experiments such as COSY and NOESY. The conformational analysis of the A ring of these compounds indicates a ‘normal’ (1α,2β)‐ half‐chair conformation rather than the expected ‘inverted’ (1β,2α)‐ half‐chair conformation. Application of the modified McConnell equation for the shielding influence of the cyclopropane aids the analyses.
13C NMR of some trans‐alkoxy‐β‐methyl‐β‐nitrostyrenes
Authors: Dawson Brian A. , By Arnold W. , Avdovich Hajro W.
Published: May 2005

13C NMR chemical shift assignments for 30 trans‐alkoxy‐β‐methyl‐β‐nitrostyrenes and the parent compound were measured and interpreted. Chemical shift assignments for 20 of these compounds have not been reported previously. Data are based on a number of 1D and 2D experiments performed at 9.4 T.
Molecular complexes of explosives with cyclodextrins I. Characterization of complexes with the nitramines RDX, HMX and TNAZ in solution by 1H NMR spin‐lattice relaxation time measurements
Authors: Cahill S. , Bulusu S.
Published: May 2005

Inclusion complex formation between the explosive molecules of the nitramine type, RDX, HMX and TNAZ, and cyclodextrins (α, β and γ) was studied in aqueous solution by means of 1H spin–lattice relaxation time (T1) measurements. The results show that nitramines bind to cyclodextrins in solution; RDX and HMX bind most strongly to γ‐cyclodextrin whereas TNAZ binds most strongly to β‐cyclodextrin. The dynamic coupling coefficient and dissociation constant were determined for the complex of TNAZ with β‐cyclodextrin. The values obtained suggest that TNAZ forms a relatively weak complex with β‐cyclodextrin (Kd = 1.8 × 10−2 M) that displays considerable motion in the complex with respect to cyclodextrin (coupling coefficient = 0.23). This method of using 1H T1 measurements for characterizing complex formation in solution, while limited to guest molecules containing a pair of protons having a fixed internuclear distance, is shown to be useful when complexation‐induced chemical shifts are too small to be significant.
Interaction of phosphorylated molecules with protic solvents and cations. Discussion of the electronic perturbation at the phosphoryl bond of triphenylphosphine oxide
Authors: Hargé Jean‐Claude , Abdallaoui Habib El Alaoui El , Rubini Patrice
Published: May 2005

Longitudinal relaxation times T1 of the 31P nucleus of triphenylphosphine oxide (TPPO) in the complexes Mg(TPPO)4(CF3SO3)2 and Cd(TPPO)4(BF4)2 were measured in nitromethane solutions at three different frequencies, leading to the determination of the chemical shift anisotropy (CSA) contribution to the total relaxation rate. The 31P shielding tensor anisotropy Δσ was measured from NMR static spectra recorded on solid samples, allowing the deduction of correlation times τr corresponding to the reorientation of the species in solution. From the line width of the 17O NMR signal, the 17O quadrupolar coupling constant χ was calculated, the value changing significantly from the free ligand (χ = 4.7 MHz) to bound molecules in complexes (χ = 6.7–7.2 MHz). This was explained by a modification of the electronic distribution around the oxygen atom, mainly due to less π back‐donation from O to P; π‐electron transfer was quantified from χ values using the Townes‐Dailey model. The nature of the interaction with these divalent cations is also discussed. The interaction of TPPO with protic solvents such as water, methanol, trifluoroacetic acid and sulphuric acid was studied using a‐procedure similar to that used for complexes, except for the determination of τr, which was reached from 13C relaxation time measurements on the para‐carbons of the phenyl groups. Variations of Δσ and χ are discussed in terms of hydrogen bonding and interaction with hydrogen ions.
NMR studies on bridged polycyclic compounds: Spin system transitions due to induced solvent shifts
Authors: Ramey Kermit C. , Moriarty Robert M. , Gopal Harsh , Adams Timothy
Published: May 2005

An NMR study of some bridged bicyclo and tricyclo compounds yielded unusual spectra with respect to solvent effects and virtual coupling. As is the general case for most large polycyclic systems a complete analysis of the spectrum is not possible and the structural details derived from NMR are based on a partial analysis of the spectrum. If the accessible resonances correspond to protons adjacent to methylene groups, the resonance patterns and the chemical shifts may be strongly dependent upon solvent. For 6‐endo‐hydroxy, bicyclo[2.2.1]heptane‐2,endo‐carboxylic acid lactone (1), 6‐endo‐hydroxy, 2‐exo‐methyl‐bicyclo[2.2.2]octane‐2‐endo‐carboxylic acid lactone (2), and exo‐3,4,exo‐8,9‐diepoxy, endo‐tricyclo[5,2,1,02,6]decane (3), resonances for each fall in this class and the change induced by solvent are attributed to virtual coupling as well as a change in the overall splitting pattern.
NMR studies of substituted pyridines
Authors: Gerig J. T. , Reinheimer John D.
Published: May 2005

Proton magnetic resonance chemical shifts and coupling constants for a series of 2‐substituted‐5‐nitropyridines and 2‐substituted‐3‐nitropyridines, both in the free base and protonated forms, are reported. The substituents were chloro, bromo, iodo, and hydroxyl. The effect of the substituents on the chemical shifts are substantial but not unusual. The coupling constants are less sensitive to the nature of the substituent and are perturbed only slightly when the ring nitrogen is protonated. This latter observation is consistent with the results of LCAO‐MO calculations.
Chemical shifts in methylcyclohexane
Authors: Lambert Joseph B. , Takeuchi Yoshinobu
Published: May 2005

In order to determine the effect of a single methyl group on the chemical shifts of protons in a cyclohexane ring, methylcyclohexane‐1,2,3,3,5,5,‐d6 has been synthesized. The protons in the 4‐position and the 2,6‐equatorial protons are not significantly different from those in ring‐frozen cyclohexane. The 2,6‐axial protons, however, experience an up‐field shift of about 15 Hz from the position of the other axial protons. These observations are discussed in terms of the structure of methylcyclohexane.
Protonenresonanz‐Spektroskopische Untersuchungen am Acetyl‐cyclobutadien‐eisentricarbonyl. Ein Beitrag zur Kenntnis der Bindungsverhältnisse im Komplex Gebundenen Cyclobutadien
Authors: Brune Hans Albert , Hüther Hans , Wolf Rochus , Körber Ingo
Published: May 2005

Das Protonenresonanz‐Spektrum des Acetyl‐cyclobutadien‐eisentricarbonyls wurde einschließlich aller beobachtbaren 13CH‐Kopplungskonstanten vermessen. Die Kopplungen warden zugeordnet und im Hinblick auf Molekülstruktur und Bindungsverhältnisse diskutiert. Auf Grund der Messungen kann die Struktur eines cyclisch‐konjugierten Diens mit alternierenden Doppel‐ und Eingachbindungen ausgeschlossen warden.
PMR studies of the deuteration and hydration of 4‐piperidones
Authors: Hassan M. M. A. , Casy A. F.
Published: May 2005

PMR spectra of substituted 4‐piperidones in base and salt forms in D2O, water and other solvents are reported, and spectral characteristics interpreted in terms of equilibria between free ketone and 4,4‐dideuteroxy (or hydroxy) forms. It is shown that 1‐mono and 1,3‐disubstituted‐4‐piperidones exist extensively as the corresponding dideuteroxy (or hydrated) species in D2O (or H2O) provided the ring nitrogen atom is positively charged, and that 3‐substituents decrease the population of these forms. The facile D/H exchange of α‐protons in the piperidone bases is also demonstrated.
Solvent effects in NMR spectra induced by aromatic solvents in 1,4‐dioxanes, 1,3‐dioxolanes and in sulphur analogues
Authors: Alexandrou N. E. , Hadjimihalakis P. M.
Published: May 2005

NMR solvent effects induced by aromatic solvents on some 1,4‐dioxanes, 1,3‐dioxolanes and on some sulphur analogue derivatives are reported. The shielding effect of the aromatic solvents is examined in respect to the structure of the solute.
The proton magnetic resonance spectrum of 1‐methylpyrazole
Authors: Batterham T. J. , Bigum C.
Published: May 2005

5‐Deutero‐1‐methylpyrazole was synthesised and used to assign multiplets in the PMR spectrum of 1‐methylpyrazole.
Konformative Beweglichkeit Flexibler Ringsysteme—XIII: Untersuchungen mit Hilfe der Protonenresonanzspektroskopie die Konformation des Ungesättigten Siebenringes im Benzocyclohepten und in symmetrisch substituierten derivaten
Authors: Kabuß S. , Schmid H. G. , Friebolin H. , Faißt W.
Published: May 2005

Für 4.4.6.6‐Tetradeuterium‐1.2‐benzocyclohepten‐(1) (1) und fünf Benzocyclo‐heptenderivate wurde PR‐specktroskopisch die Konformation des ungesättigten Siebenringes bestimmt. Bei allen untersuchten Verbindungen liegt bei −80° nur ein Konformeres in nachweisbarer Menge vor. Durch Auswertung PR‐spektroskopisch bestimmter Daten – Molekel‐Symmetrie, Kopplungskonstanten, chemische Verschiebungen – kann gezeigt werden, daß dieses Konformere Sesselform hat. Die freie Konformationsenthalpie der beiden anderen Konformeren mit Wannen‐ bzw. Twist‐Form des Siebenringes beträgt bei allen sechs Verbindungen mehr als 1,8 kcal/Mol.

Mit den experimentellen Ergebnissen stimmen diejenigen von Modellrechnungen überein: Für die Molekeln des Benzocycloheptens sowie des 5.5‐Dimethylderivates (2) und der 4.4.6.6‐Tetramethylverbindung (4) wurde für die Sesselkonformation der niedrigste Energieinhalt berechnet; als zweitstabilste Konformation wurde bei 1 und 4 die Wanne, bei 2 hingegen die Twist‐Form ermittelt.
Proton magnetic resonance studies of tautomerism in substituted pyrimidines
Authors: Glasel Jay A.
Published: May 2005

Studies of line width and chemical shift vs. temperature for amide and hydroxyl proton magnetic resonance signals from: barbituric acid, dialuric acid, parabanic acid, alloxan and alloxan monohydrate dissolved in anhydrous dimethyl sulfoxide‐d6 are reported. The behavior of the amide signals shows that, between 20 and 65°C, none of the compounds listed exhibits lactim‐lactam tautomerism. The amide proton resonance in uracil has also been investigated. The signal is a closely spaced, equal intensity, doublet due to the non‐equivalence of H(1) and H(3). Again, no evidence of tautomerism is observed. Activation energies for the hydroxyl resonances in dialuric acid and alloxan monohydrate indicate hydrogen bonding between solute and solvent. The results of simple LCAO‐MO calculations are in accord with the experimental conclusions concerning tautomeric equilibria.
Die Konformeren des 5,5‐Dimethyl‐3,7‐dithia‐1,2‐benzocycloheptens‐(1) und ihre Umwandlungen Konformative Beweglichkeit flexibler Ringsysteme—XV. Untersuchungen mit Hilfe der Protonenresonanzspektroskopie
Authors: von Bredow K. , Friebolin H. , Kabuß S.
Published: May 2005

Die Temperaturabhängigkeit der Protonenresonanzen (PR) des 5.5‐Dimethyl‐3.7‐dithia‐1.2‐benzocycloheptens‐(1) wird beschrieben und diskutiert. Diese Verbindung liegt in zwei Konformeren mit unterschiedlicher Topographie des Siebenringes vor. Anhand der den Tieftemperatur‐spektren entnommenen Werten der chemischen Verschiebung der Signale geminaler Methylgruppen wird gezeigt, daß der Siebenring bei einem dieser Konformeren Sessel‐, beim anderen Twistform hat. Die freie Konformationsenthalpie des Twistkonformeren beträgt nur etwa 20 cal/Mol. Zwei konformative Umwandlungsprozesse können kinetisch verfolgt werden: Die Version zwischen Sessel‐ und Twist‐Konformationen und die Pseudorotation der Twist‐Konformationen. Die freie Aktivierungsenthalpie ΔGv≠ der Version berträgt 12,6 ± 0,1 kcal/Mol(bei − 12°C), die freie Aktivierungsenthalpie ΔGP≠ der Pseudorotation 8.3 ± 0.3 kcal/Mol (bei −95°C).
Etude par RMN de la Structure des Cyano‐2 Alcoyl‐2 Norbornenes‐5
Authors: Muller J. C. , Fleury J. P. , Scheidegger U.
Published: May 2005

L'attribution de structure des deux isomères cyano‐2 alcoyl‐2 norbornène‐5 est possible grǎce aux données de la RMN. Une interprétation des spectres de ces dérivés bicycliques set donnée. Dans le cas des cyano‐2 méthyl‐2 norbornènes‐5 une confirmation de structure a pu ětre donnée par voie chimique (hydrolyse basique et iodolactonisation).
Carbon‐13 chemical shifts of α,β‐unsaturated acids
Authors: Lippmaa E. , Pehk T. , Andersson K. , Rappe C.
Published: May 2005

Carbon‐13 spectra of 59 α,β‐unsaturated carboxylic acids have been measured. Large differential shieldings of ethylenic carbons in the cis and trans isomers of acrylic acid derivatives were found (altogether 15 isomeric Z‐ and E‐pairs of acids were investigated). The origin of differential shieldings is complex and both molecular ground states as well as changes in excited states appear to be involved. All measured 13C chemical shifts can be described by additive parameters that provide a straightforward new technique by which structural assignments can be made for a wide variety of isomeric mono‐, di‐ and tri‐ substituted α,β‐unsaturated acids.
The structure of trisformamidomethane in dimethyl sulphoxide‐d6, hexamethylphos‐phortriamide and trifluoroacetic acid
Authors: Armarego W. L. F. , Kobayashi Toshihiko
Published: May 2005

The PMR spectrum of trisformamidomethane in dimethyl sulphoxide‐d6 and hexamethyl‐phosphortriamide has been explained by postulating four major structures in solution: two rotamers and two structural isomers, all of which are stabilized by intramolecular hydrogen bonding to form six membered rings. The spectrum in trifluoroacetic acid is also described.
Analyse Conformationnelle en Serie Alcoylidene‐5 Dioxanne‐1,3
Authors: Desaulles Philippe , Fleury Jean‐Pierre
Published: May 2005

Un certain nombre d'alcoylidène‐5 alcoyl‐2 dioxannes‐1,3 ont été étudiés par RMN. L'analyse des spectres permet de conclure à une conformation chaise prédominante de ces dérivés, le substituant alcoyle sur carbone 2 se plaçant en position équatorial. Pour les alcoylidène‐5 dioxannes‐1,3 non substitués sur carbone 2 il y a inversion rapide du cycle avec une barrière énergétique extrěmement faible.
High‐resolution nuclear magnetic resonance spectra of phenanthrenes–IV Phenyl derivatives of phenanthrene
Authors: Bartle K. D. , Bavin P. M. G. , Jones D. W.
Published: May 2005

Proton magnetic resonance spectra at 60 MHz are reported for 9, 9′‐biphenanthryl, 1‐phenylfluoranthene, 9‐benzylphenanthrene, 1‐, 4‐ and 9‐phenylphenanthrenes and 9‐methyl‐10‐phenylphenanthrene, all in CS2 solution. Approximate values of some of the chemical shifts and coupling constants were extracted from the overlapped and often collapsed AB, ABC ABCD and AA′BB′C (phenyl) spin systems. By comparison with data for phenanthrene itself, estimates have been made for the dihedral angle, θ, between the planes of the phenyl ring and the phenanthrene nucleus in phenylphenanthrenes. These lead, except for 9‐phenylphenanthrene for which the angle derived from H(10) by PMR is higher than UV suggests, to plausible values for θ: 90°, 75°, 40° and 45 to 60°, for 4‐phenyl, 9‐methyl‐10‐phenyl‐, 1‐ and 9‐phenylphenanthrenes, respectively.
Spectroscopic studies on N,N‐dimethylamides—I: Structure‐reactivity correlation for rotational barriers from a nuclear magnetic resonance study of p‐ and m‐substituted N,N‐dimethylbenzamides
Authors: Korver P. K. , Spaargaren K. , van der Haak P. J. , de Boer Th. J.
Published: May 2005

Rotational barriers in 21 p‐ and m‐substituted N,N‐dimethylbenzamides in CDCl3 as solvent have been determined using the intensity ratio method of Woodbrey. These data compare very well with values from the literature1 obtained with a total line shape analysis. From structure‐reactivity correlations evidence has been obtained for a relatively strong resonance interaction between the substituent in the aromatic ring and the partially double amide bond.
New evidence of the intrinsic chemical shift non‐equivalence
Authors: Dabrowski Janusz , Ejchart Andrzej , Biernacki Władysław
Published: May 2005

Carbinols of the general formulae R·CHOH·C(NO2)Me2 exhibit increasing values of chemical shift non‐equivalence for the geminal methyl groups with rise of temperature. This phenomenon furnishes indirect evidence for the intrinsic non‐equivalence.
1H magnetic resonance spectroscopy of some substituted acetophenones
Authors: Bloxsidge J. , Jones J. R. , Marks R. E.
Published: May 2005

Measurements are reported on the nuclear magnetic resonance spectra of the acetyl protons of a series of substituted acetophenones. Although the extreme values of the chemical shifts, δ for the meta‐ and para‐ substituted compounds differ only by 0·2 units, the values themselves are linearly related to the Hammett substituent constants. No such relationship exists for the ortho‐substituted compounds. The magnitude of the chemical shift is independent of substrate concentration over a five‐fold variation.
Spectroscopic studies on olefins—III: NMR of cis‐ and trans‐ disubstituted olefins
Authors: Rummens F. H. A. , de Haan J. W.
Published: May 2005

The proton NMR spectra of four cis/trans pairs of 1,2‐disubstituted olefins have been analysed. The observed trends of the olefinic, vicinal and allylic proton‐proton coupling constants are discussed in terms of rehybridization at the sp2 carbon atoms. It is found that in these substances the trans‐allylic couplings are generally more negative than the cis‐allylic couplings contrary to Barfield's1 theoretical prediction but in agreement with some earlier experimental data. Steric hindrance between cisoid substituents is cited as the probable origin of this end related trends.
Dérivés Alléniques de l'Étain, du Plomb et du Mercure. Signes Relatifs des Constantes de Couplage Métal‐Proton á Travers Deux et Quatre Liaisons
Authors: Simonnin Marie‐Paule , Lequan Minh , Lecourt Marie‐José
Published: May 2005

Les spectres de Dérivés alléniques du plomb, de l'étain et du mercure permettent d'observer les satellites dûs aux couplages métal‐proton à travers deux et quatre liaisons. L'analyse de ces satellites montre que 2J(XH) et 4J(XH) sont de signes contraires pour X = 207Pb, 119Sn, 117Sn et de même signe pour X = 199Hg.

Les signes absolus probables des constantes de couplage réduites sont discutés en fonction des résultats de la littérature: 2K(XCH) est très probablement positif pour X = 207Pb, 119Sn, 117Sn et 199Hg.

4K(XCCCH) est probablement négatif pour X = 207Pb, 119Sn, 117Sn, et positif pour X = 199Hg.
Stereochemical characterization of some mono‐ and diaryl substituted ethylene oxides by NMR spectroscopy
Authors: Ceccarelli Giulio , Berti Giancarlo , Lippi Giorgio , Macchia Bruno
Published: May 2005

NMR spectra of several styrene, stilbene and stilbazole oxides have been determined, and chemical shifts and coupling constants have been correlated with cis‐and trans‐configurations. Assignments have been made for all protons, and double resonance technique and 13CH coupling constants have been used in some particular cases. An explanation is proposed for the observation that chemical shifts of oxirane protons are higher for cis than for trans isomers.
High resolution proton magnetic resonance spectra of heterocyclics 1,4‐benzodithiin and 1,4‐benzodioxin
Authors: Deb K. K. , Bloor J. E. , Cole T. C.
Published: May 2005

The proton magnetic resonance spectra of 1,4‐benzodithiin and 1,4‐benzodioxin have been fully analyzed. The effects of the substituent heteroatoms on the chemical shifts of the various protons in the two molecules have been discussed.
Protonenresonanz‐Untersuchungen an Polysaccharid‐Derivaten—II: CELLULOSEDERIVATE
Authors: Friebolin H. , Keilich G. , Siefert E.
Published: May 2005

Am Beispiel der Cellulosederivate wurde gezeigt, wie es mit Hilfe der PR‐Spektroskopie—speziell bei einer Meßfrequenz von 220 MHz—möglich ist, in Polysacchariden zwischen einer Hexose und Pentose zu unterscheiden, die Konfiguration und die Konformation des Monomerbausteins im Polymeren sowie die Art der glycosidischen Bindung zu bestimmen. Voraussetzung für diese Untersuchungen sind die Acetyl‐, Benzoyl‐ oder Methylderivate des Polysaccharids, wobei der Polymerisationsgrad bei den Acetaten und den Methyläthern Pw < 200, bei den Benzoaten sogar Pw < 100 sein sollte.
Further evidence of the intrinsic chemical shift non‐equivalence
Authors: Dąbrowski Janusz , Ejchart Andrzej , Biernacki Władysław
Published: May 2005

The influence of hydrogen bonds on the chemical shift non‐equivalence of geminal methyl groups in recently investigated carbinols has been eliminated by using the formyl derivatives of the general formula RCH(OCHO)C(NO2)Me2. The observed increasing non‐equivalence, with the rise of temperature, provides more convincing evidence of the intrinsic non‐equivalence.
Carbon‐13 chemical shifts of bicyclic compounds
Authors: Lippmaa E. , Pehk T. , Paasivirta J. , Belikova N. , Platé A.
Published: May 2005

13C NMR absorption spectra of 50 bicyclic hydrocarbons, alcohols and ketones have been measured, in addition to some terpenes. The 13C chemical shifts are approximately additive for similar compounds and can be used for the determination of molecular structure; they differ for endo‐ and exo‐isomers, just as in proton spectra. These quite regular and predictable 13C shift differences are much larger and are caused by the 1,4‐nonbonded interaction between atoms heavier than hydrogen, not by magnetic anisotropy effects.
Kernresonanzspektroskopische Untersuchungen an 3‐aza‐bicyclo[3.1.0]hexanen
Authors: Wendisch Detlef , Naegele Walter
Published: May 2005

Es werden die kernresonanzspektroskopischen Parameter von drei 3‐Aza‐bicyclo[3.1.0]hexanen mitgeteilt, die aus den 100‐ und 220 MHz‐ Spektren durch Teilanalyse bzw. Durch iterative Computerberechnungen ermittelt wurden. Eine kurze Diskussion der erhaltenen Parameter in Hinblick auf die Struktur des 3‐Aza‐bicyclo[3 1.0]hexan‐Systems schließt sich an.
NMR spectra of Δ3‐ and Δ4‐pyrrolin‐2‐one
Authors: Mondelli R. , Bocchi V. , Gardini G. P. , Chierici L.
Published: May 2005

The spectra of Δ3‐ and Δ4‐pyrrolin‐2‐one were analysed and the sign of all the coupling constants determined by tickling and triple resonance experiments. A positive allylic interaction (Jxz in 2) is reported and four‐bond couplings are discussed in particular. Deuterium exchange affords evidence for the tautomeric equilibrium between 1 and 2.
Isomérie Polyédrique dans des Spirophosphoranes Possédant le Groupement PH
Authors: Houalla D. , Sanchez M. , Beslier L. , Wolf R.
Published: May 2005

Nous avons étudié la variation, en fonction de la température, des spectres de RMN de six spirophosphoranes des types: magnified image

Les résultats expérimentaux indiquent l'existence d'une isomérie intramoléculaire que nous avons interprétée en adoptant le mécanisme de pseudo‐rotation proposé par Berry.1

Dans tous les cas, sauf un, le déplacement de l'équilibre tautomère spirophosphorane ⇌ phosphite s'ajoute an phénomène d'isomérie observé.
Heterocycles Contenant du Phosphore—V. Analyse des Spectres de Resonance Magnetique Protonique des Oxo‐2 Methoxy ou Phénoxy‐2, Methyl‐3, Oxazaphospholanes‐1,3,2: Exemples de Spectres du type ABXY
Authors: Devillers Jean , Navech Jacques , Albrand Jean‐Pierre
Published: May 2005

Les 2 oxazaphospholanes étudiés ici donnent des spectres de RMP qui, après découplage du phosphore, peuvent ětre analysés comme des ABXY. Sur les huit solutions possibles, six peuvent ětre aisément éliminées et deux expériences de ‘tickling’ permettent de choisir entre les deux restantes. L'accord entre les spectres calculés, avec le programme LAOCOON III, et les spectres expérimentaux est très bon. La doubel résonance hétéronucléaire, les expériences de ‘tickling’ ou d'‘Indor’ permettent de déterminer les signes relatifs des constantes de couplages 3J(POCH) et 3J(PNCH). On vérifie également par l'expérience qu'aux signes négatifs de 2J HH correspondent des signes positifs pour les 3J HH. Quant à la conformation du cycle, si on ne peut l'établir avec certitude, on peut cependant constater, par comparaison avec les dioxaphospholanes, que l'introduction d'un groupement NCH3 ne semble pas introduire de dissymétrie et que le couplage 3J(PNCH) semble avoir une dépendance stéréochimique comparable à 3J(POCH).
The NMR‐spectrum of benzaldehyde partially oriented in the nematic phase
Authors: Diehl P. , Henrichs P. M. , Niederberger W.
Published: May 2005

The NMR spectrum of benzaldehyde oriented in the nematic phase of a mixture of p‐(p‐ethoxyphenylazo)phenylheptanoate and p‐(p‐ethoxyphenylazo)phenylundecylenate is analysed. It is demonstrated that the data are inconsistent with models in which the aldehyde group freely rotates or has minimum energy when it is perpendicular to the ring plane. The barrier height to rotation, however, cannot be obtained, nor is it possible to discriminate between the two possible solutions in which the averaging planar forms do or do not reorient in the liquid crystal between successive internal rotations.
Solvent effects in NMR spectra induced by benzene in aromatic N‐alkyl nitrones and O‐alkyl oximes—III
Authors: Alexandrou N. E. , Varvoglis A. G.
Published: May 2005

NMR solvent effects induced by benzene on several N‐ and O‐alkyl oximes are reported. Both shielding and deshielding effects are observed and are accounted for by the geometry of the solute‐solvent ‘complex’. Good Hammett plots of solvent shifts for various types of protons are obtained.
Etude Conformationnelle d'Aldehydes a‐Thiopheniques et Furanniques par RMN
Authors: Roques B. , Fournie‐Zaluski M. C.
Published: May 2005

Nous avons effectué l'étude par RMN d'aldéhydes α‐thiophéniques et furanniques substitués et déterminé leurs conformations préférentielles par examen des valeurs des couplages stéréo‐spécifiques. On observe des modifications de la conformation du groupement aldéhydique en fonction de la nature des substituants placés en ortho. La conformation préférentielle de ces aldéhydes hétérocycliques est interprétée en fonction de l'existence de trois termes d'interactions.
Nuclear magnetic resonance spectra of carbanions—III: Tetraphenylethylene dianion
Authors: Takahashi Kensuke , Inoue Yoshio , Asami Ryuzo
Published: May 2005

The PMR spectra of the titled carbanion have been observed well‐resolved and suitable for first‐order analysis. Excess charges localized in the phenyl rings are estimated from the chemical shifts and compared with those observed in other carbanions.
Acetate‐methyl signals in the nuclear magnetic resonance spectra of peracetylated derivatives of some oligo‐ and polysaccharides
Authors: Hirano Shigehiro
Published: May 2005

Peracetyl derivatives of oligo‐ and polysaccharides showed their own characteristic acetate‐methyl signals in the NMR spectra measured in chloroform‐d, which are useful for the identification and conformational analysis of oligo‐ and polysaccharides in solutions. An acetate‐methyl signal in the lowest field among three acetate‐methyl signals appeared in the NMR spectra of amylose acetate and was assigned to the acetate‐methyl signal at C6 on the basis of acetate‐methyl signals of peracetylated derivatives of 6‐O‐tosylamylose and xylan. Monosaccharide moieties in oligo‐ and polysaccharides examined were found in the C1 (D) conformation.
Distortion analysis of severely flattened rings
Authors: Lambert Joseph B. , Koeng Fred R.
Published: May 2005

The NMR spectra of the nonaromatic protons in several benzo‐substituted five‐ and six‐membered rings have been analyzed at 60‐ and 90‐MHz. The vicinal coupling constants from theCH2CH2fragments give a quantitative assessment of the degree of ring flattening. The distortions are discussed in terms of the structural components of the molecules.
Solvent effect on chemical shift non‐equivalence of methylene protons in dibenzyl‐, diphenacyl‐ and benzyl phenacyl sulphoxides
Authors: Sataty Ishai
Published: May 2005

The methylene protons of dibenzyl sulphoxide are magnetically equivalent in low dielectric and non‐equivalent in high dielectric constant solvents, while for diphenacyl sulphoxide this behaviour is reversed. In both cases, the variation in the magnitude of the non‐equivalence reflects a greater downfield shift of one methylene proton than the other on passing from non‐polar to polar solvents. By contrast, the chemical shift difference between the benzyl methylene protons or between the phenacyl methylene protons of benzyl phenacyl sulphoxide varies only slightly with solvent polarity.