bluuebunny/crossref_metadata_2025_split huggingface dataset:
Passive observation of 15N satellites in two‐dimensional heteronuclear X–1H shift‐correlated spectra via a Hahn spin–echo extended pulse sequence
Authors: Kupče Ēriks , Wrackmeyer Bernd 
Published: May 2005

AbstractThe application of a Hahn spin–echo extended X–1H shift‐correlated (X = 13C, 29Si, 119Sn, 207Pb) two‐dimensional NMR technique to carbon–, silicon–, tin– and lead–nitrogen compounds is described. This allows complete suppression of the central line (representing the isotopomer with 14N), leaving solely the 15N satellites in the two‐dimensional spectrum leading both to accurate measurement of long‐range 15N1H spin–spin coupling constants and to the determination of the relative signs of the 15NX and 15N1H couplings. 15N/14N isotope effects on 119Sn and 207Pb chemical shifts were measured apparently for the first time.
Fluorine deshielding in the proximity of a methyl group. An experimental and theoretical study
Authors: Gribble Gordon W. , Keavy Daniel J. , Olson Erik R. , Rae Ian D. , Staffa Alfred , Herr Tomas E. , Ferraro Marta B. , Contreras Rubén H. 
Published: May 2005

Abstract19F chemical shifts are reported for a series of alkyl‐substituted fluoronaphthalenes and related compounds that exhibit steric crowding around the fluorine atom due to the proximity of methyl groups. Comparisons of these chemical shifts with others measured in similar compounds but without the corresponding methyl groups show that this crowding effect produces a large low‐field shift of the 19F signal. Similar effects, but with an even larger sensitivity to the steric crowding, were recently reported for 17O chemical shifts. The electronic origin for this proximity effect on 19F chemical shifts is analyzed within the molecular orbital theory, at the INDO level, using the inner projections of the polarization propagator technique. It is found that the presence of the methyl group produces an increase in the absolute value of the paramagnetic term of the magnetic shielding constant.
NMR lipid profiles of cells, tissues and body fluids. I— 1D and 2D Proton NMR of lipids from rat liver
Authors: Casu Mariano , Anderson Graeme J. , Choi Gregory , Gibbons William A. 
Published: May 2005

AbstractA combination of established lipid extraction procedures and high‐resolution 1D and 2D NMR spectroscopic methods has been used to analyse qualitatively and quantitatively the lipid composition of rat liver. The major lipids present in each structural class were identified and quantified. Considerable information on the composition of the different classes of structural and unsaturated fatty acid chains were obtained for the intact lipids without resort to hydrolysis. Significantly, the relative amounts of cholesterol, glycerophospholipids, ether lipids, sphingolipids and glycerides were shown to be in agreement with previous determinations by high‐performance liquid and other chromatographic procedures.
NMR spectroscopic properties of heptakis(2,6‐di‐O‐pentyl)‐β‐cyclodextrin: Two‐dimensional NMR spectra of a key intermediate in preparing chiral stationary phases for enantioselective capillary gas chromatography
Authors: Meier‐Augenstein Wolfram , Burger Barend V. , Spies Hendrik S. C. 
Published: May 2005

AbstractThe 1H and 13C NMR spectra of heptakis(2,6‐di‐O‐pentyl)‐β‐cyclodextrin in deuteriochloroform have been fully and unambiguously assigned. Several methods, including homo‐ and heteronuclear spin decoupling, two‐dimensional homo‐ and hetero‐nuclear correlation NMR spectroscopy, spectral simulation and the measurement of relaxation times were used for chemical shift assignments.
Nuclear quadrupole resonance in chloromethylphenols
Authors: Kalathimattam Roy Sebastian , Bai Amitha , Uchil Jayagopal 
Published: May 2005

AbstractThe temperature dependences of the 35Cl nuclear quadrupole resonance (NQR) frequencies of 4‐chloro‐3‐methyl‐, 2‐chloro‐5‐methyl‐ and 4‐chloro‐2‐methyl‐phenol were studied in the temperature range from 77 K up to the respective melting points. 4‐Chloro‐2‐methylphenol undergoes a phase transition at ca 185 K, and the presence of trans–cis isomeric forms is inferred. The NQR frequencies of molecules at absolute zero temperature were evaluated.
Stereochemistry of 3‐arylideneflavanones and their thio analogues by the use of 3J(CH) couplings
Authors: Tóth Gábor , Szöllösy Åron , Lévai Albert , Oszbach György , Dietrich Wolfgang , Kühne Harald 
Published: May 2005

AbstractThe application of the 3J(HCXC) couplings in 3‐arylideneflavanones and 3‐arylidenethioflavanones allows a semi‐quantitative estimation of the conformational equilibrium.
NMR and conformational studies of the cyclobutane ring involved in the bicyclo [4.2.0]octane system of a tetracyclic diterpene structure
Authors: Manh Duc Do Khac , Fetizon Marcel , Prévost Chantal , Roy Pierre 
Published: May 2005

AbstractConformational studies were performed on the bicyclo [4.2.0] octane system of a series of related tetracyclic diterpenes, using molecular mechanics and 1H NMR. Both methods gave compatible results, but did not permit the deduction of any quantitative relationship linking the vicinal coupling constants to the cyclobutane dihedral angles. Nevertheless, the Karplus relationship allowed a qualitative interpretation of the coupling constants in terms of conformation. A set of characteristic 1H NMR coupling constants was obtained which allows the interpretation of the 1H NMR spectrum of any compound presenting a similar system.
Inclusion complexes between β‐cyclodextrin and β‐benzyloxy‐α‐propionic derivatives of paramagnetic DOTA‐ and DPTA‐Gd(III) complexes
Authors: Aime Silvio , Botta Mauro , Panero Maurizio , Grandi Maurizio , Uggeri Fulvio 
Published: May 2005

AbstractThe addition of β‐cyclodextrin to a solution containing β‐benzyloxy‐α‐propionic‐substituted DOTA‐ and DTPA‐Gd(III) complexes leads to the formation of inclusion compounds whose equilibrium constants have been determined by NMR titrations. The main effect associated with the formation of this ‘host‐uest’ interaction is a marked elongation of the molecular reorientational time, τr, which in turn results in increased solvent proton relaxation rates.
Intermolecular and intramolecular effects on the 1H and 13C shielding in some gaseous hydrocarbons at various temperatures—experimental results
Authors: Bennett Brian , Raynes William Thomas 
Published: May 2005

AbstractThe proton and 13C shielding constants in CH4, C2H6, C3H8, and some other gaseous hydrocarbons have been studied as functions of density at temperatures in the range 180–370 K. The linear coefficients describing the density dependence of the shielding, after correcting for bulk susceptibility, increase substantially as the temperature is reduced, indicating stronger intermolecular interactions. (Some of the required magnetic susceptibilities were determined in this work by an NMR method). The 13C measurements for CH4 are close to those of an earlier study; the results for the other gases are new. The linear coefficient is substantially greater for the carbon shielding of the methyl group in propane than for the methylene group at any temperature, but there is virtually no distinction between the linear coefficients for the proton shielding in this gas. Values for do0/dT, the temperature dependence of the shielding extrapolated to zero density, are also presented for both proton and 13C shielding in the hydrocarbons. They are positive and negative in different instances. It is shown from this and earlier gas‐phase studies that standard literature values of the methane 13C shielding relative to the 13 shielding in the other hydrocarbons are in error.
Quantitative empirical treatment of 13C NMR chemical shifts of aliphatic halides
Authors: Suryanarayana Iragavarapu , Gasteiger Johann 
Published: May 2005

AbstractThe 13C NMR chemical shifts of the α, β, γ and δ carbons of aliphatic fluorides, chlorides, bromides and iodides can be reproduced by a four‐parameter equation; the charge Q on the carbon atom, the number of hydrogen atoms three bonds away, N3H, the interactions of the polarizabilities of the halogen atoms one bond away with the hydrogens present in the first sphere, as represented by PXN1H, and the polarizabilities of halogens in the second sphere, PX(2). A regression coefficient of 0.9714 and a standard deviation of 4.85 ppm are obtained for all aliphatic halides in which the R skeleton includes alkyl, acyclic and bicyclic rings. For alkyl compounds only the correlation is of the order of R = 0.997 and the standard deviation is less than 2 ppm. Here the influence of C, H, F, Cl, Br and I are reproduced quantitatively.
Complete 1H and 13C NMR assignments of ruthenium(II) complexes with two new 2‐pyridylquinoline ligands
Authors: Finocchiaro Paolo , Mamo Antonino , Tringali Corrado 
Published: May 2005

AbstractThe complete assignment of the proton and carbon spectra for two new 2‐pyridylquinoline ligands, 4‐phenyl‐2‐(2′‐pyridyl)quinoline (Ph‐pq) and 2,6‐di(4′‐phenylquinol‐2′‐yl)pyridine (Ph‐dqp), and their ruthenium(II) complexes [Ru(bpy)2(Ph‐pq)](PF6)2 and [Ru(Ph‐dqp)2](PF6)2 has been accomplished using a combination of one‐ and two‐dimensional NMR techniques, including COSY, NOESY, one‐bond and long‐range HETCOR and selective INEPT spectra. The J(H,H) and J(C,H) values have been determined for the majority of the resonances.
Structure of [RhH2(PPh3)2(bipy)]Cl (bipy = 2,2′‐bipyridyl) from multinuclear NMR studies
Authors: Heaton B. T. , Jacob C. , Heggie W. , Page P. R. , Villax I. 
Published: May 2005

AbstractBy the use of the INEPT pulse sequence it has been possible to obtain 15N and 103Rh NMR data on [RhH2(PPh3)2(bipy)]Cl (bipy = 2,2′‐bipyridyl) containing natural abundance 15N and prove the stereochemistry; 1H and 31P NMR data are also reported for [RhH2(PPh3)2(bipy)]Cl which can be easily prepared in the pure state by the reaction of [RhCl(PPh3)3] or [Rh2Cl2(PPh3)4] with bipy ([Rh]: [bipy] = 1:1) under an H2 atmosphere.
Variable‐pressure oxygen‐17 NMR study of water exchange on hexaaquarhodium(III)
Authors: Laurenczy Gábor , Rapaport Irina , Zbinden Donald , Merbach André E. 
Published: May 2005

AbstractRate constants and activation parameters for water exchange on hexaaqua‐ and monohydroxypentaaquarhodium(III) were determined by 17O NMR as a function of temperature (323–364 K) and pressure (up to 210 MPa, at 323 K) at several acidities (1.0–5.0 molal HClO4). The observed rate constant was of the form kex = k1 + k2/[H+], where the subscripts 1 and 2 refer to the exchange pathways on Rh(H2O)63+ and Rh(H2O)5(OH)2+, respectively. The kinetic parameters are as follows: k1298 = 2.2 × 10−9 s−1, ΔH1‡ = 131 ± 23 kJ mol−1, ΔS1‡ = + 29 ± 69 J K−1 mol−1, ΔV1‡ = −4.2 ± 0.6 cm3 mol−1; k2298 = 1.5 × 10−8 m s−1, ΔH2‡ = 136 ± 7 kJ mol−1, ΔS2‡ = + 61 ± 21 J K−1 mol−1, ΔV2‡ = + 1.3 ± 0.3 cm3 mol−1. The thermodynamic parameters for the acid dissociation reaction of Rh(H2O)63+ were determined potentiometrically and spectrophotometrically: pKa298 = 3.45 and ΔVa0 = −0.2 ± 0.5 cm3 mol−1. Values were estimated for the first‐order rate constant (using the relationship k2 = kOHKa) and the corresponding activation volume for Rh(H2O)5(OH)2+: kOH298 = 4.2 × 10−5 s−1 and ΔVOH‡ = + 1.5 cm3 mol−1. The kinetic results imply an associative interchange mechanism Ia for Rh(H2O)63+ and an interchange mechanism I with a slight dissociative character for the strongly OH labilized Rh(H2O)5(OH)2+ species.
13C and 1H NMR chemical shift assignments of 1‐ and 2‐alkylnaphthalenes (R = Me, Et, i‐Pr, t‐Bu) and determination of substituent effects on 13C and 1H chemical shifts
Authors: Ernst Ludger , Schulz Petra 
Published: May 2005

AbstractComplete 13C spectral assignments were made for 1‐ and 2‐R‐naphthalenes (R = Me, Et, i‐Pr, t‐Bu) in CDCl3 solution (5 mol%) by the use of 2D techniques including 2D INADEQUATE. Contradictory assignments from the literature were clarified and incomplete data completed. Substituent effects on 13C shifts are briefly discussed. 1H chemical shifts were determined by 13C/1H shift correlation.
Second‐order regression of 13C substituent chemical shifts with Taft's sigma constants
Authors: Holik Miroslav 
Published: May 2005

AbstractIn addition to Taft's dual substituent parameter (DSP) and DSP–non–linear resonance (DSP–NLR) models, and Charton's triple substituent parameter (TSP) equation, two second‐order regression models were tested using published data for 13C substituent chemical shifts of the C‐4 atom in 1,4‐disubstituted benzenes. The complete data matrix consisted of 14 series with a fixed Y (C‐4) substituent, each with 14 variable X (C‐1) substituents. Second‐order (in the σ parameter or in a combination of the σ1 and σ constants) models gave results as good as, and in some cases even better than, the DSP–NLR equation; the results of the TSP model were always worse. The whole data matrix was submitted to principal component analysis. Target testing has shown vectors of σ, (σ)2 and σI constants as ‘real’ principal components.
Phosphorus‐31 NMR studies of polymer‐supported highly reactive copper reagents
Authors: O'Brien R. A. , Gupta A. K. , Rieke R. D. , Shoemaker R. K. 
Published: May 2005

AbstractThe chemistry of highly reactive zerovalent copper species represents an active area of research. Recently, active metal chemistry has been successfully accomplished using polymer‐supported triphenylphosphine–copper(I) coordination complexes as precursors. Since the materials are solids, detailed examination of the reagents at vaious stages of chemical reaction can be problematic, since the primary means of examination has historically been proton, 13C and 31P NMR methods. In this study, cross‐polarization magic angle spinning (CPMAS) experiments, combined with 31P T1 relaxation measurements (via proton cross‐polarization), provided data which allowed the determination of the role of the phosphine species in the overall chemistry of these materials. Although it is known that the type of phosphine affects the chemistry, it was found here that there is no observable interaction between the reduced copper species and the polymer‐supported triphenylphosphine.
Nuclear magnetic resonance evidence for radiation damage of saturated phosphatidylcholine in bilayers
Authors: Casu Mariano , Lai Adolfo , Erriu Gianni , Onnis Salvatore , Zucca Nazario 
Published: May 2005

AbstractMultilayer membranes of 1,2‐dipalmitoyl‐sn‐glycero‐3‐phosphorylcholine were prepared in D2O and exposed to γ‐radiation. Changes in the chemical structure due to irradiation were studied by 1H, 13C and 31P NMR after lyophilization and dissolution in chloroform‐methanol (1 : 2, v/v). One‐ and two‐dimensional techniques were used. 1‐Palmitoyl‐sn‐glycero‐3‐phosphorylcholine, 2‐palmitoyl‐sn‐glycero‐3‐phosphorylcholine, glycero‐3‐phosphorylcholine and palmitic acid were identified as new components. Their development during irradiation was quantitatively determined. The results were discussed in terms of possible reaction steps responsible for the radiolytic decomposition.
1H and 13C NMR studies of substituted isoquinolinium derivatives in different solvents
Authors: Werra W. , Heber D. , Holzgrabe U. 
Published: May 2005

Abstract1H and 13C NMR data for 1‐cyano‐, 4‐cyano‐, 4‐bromo‐ and 4‐bromo‐5‐nitro‐substituted isoquinolines, isoquinoline N‐oxides and N‐methoxy and N‐ethyl salts in different solvents are reported. The substituent chemical shifts are discussed with regard to the reactivity of the N‐methoxy compounds in the presence of nucleophilic reagents.
Complete assignment and conformational studies of tomatine and tomatidine
Authors: Willker W. , Leibfritz D. 
Published: May 2005

AbstractHeteronuclear correlation techniques and homonuclear E.COSY spectra were used to obtain a complete assignment of the 13C and 1H NMR spectra of the aglycone tomatidine. In addition, 1D/2D TOCSY, NOESY and ROESY spectra allowed the assignment of the sugar moiety in tomatine. The procedure used is of general applicability for the structural elucidation of sugars and glycosidic biomolecules.
Determination of the resonance frequency ratio of the 31P and 1H NMR resonance shift standards 85% orthophosphoric acid and tetramethylsilane
Authors: Edzes Hommo T. 
Published: May 2005

AbstractThe NMR resonance frequency ratio of the 31P NMR resonance shift standard 85% orthophosphoric acid (H3PO4) and the 1H standard tetramethylsilane (TMS) was determined by means of the ‘dispersed phase’ method. The Ξ value, equal to 108 times the resonance frequency ratio, was 40480737.0 ± 0.2 Hz at 25°C. A small dependence on temperature (−0.11 Hz °C−1) and on phosphoric acid concentration (−0.50 Hz %−1) was observed around 25°C. Traces of iron in phosphoric acid were found to have a negligible effect on Ξ values, although line widths increased. The determination of Ξ allows accurate referencing of 31P NMR spectra relative to the 1H resonance of internal TMS or of a secondary 1H shift standard. The accuracy of the 31P NMR resonance shift scale is primarily limited by the uncertainty of solvent‐induced 1H resonance shifts of TMS.
Conformational analysis 18—lanthanide‐induced shift (LIS) investigation of some 2‐substituted 1,3‐dioxanes
Authors: Abraham Raymond J. , Wallace Kerry , Wilkins Suzanne , Sancassan Fernando 
Published: May 2005

AbstractA LIS analysis of 2‐isopropyl‐1,3‐dioxane (1) and 2‐methyl‐2‐phenyl‐1,3‐dioxane (2) is reported. The monodentate complexing model gives good agreement with the observed shifts in both compounds, whereas the bidentate model (lanthanum binding to both oxygens) does not give an acceptable solution. In 1 the lanthanide complexes almost exclusively (90%) with the axial lone pair of the oxygen atom. The four‐site binding model gives excellent agreement with the observed shifts (Rx 3.5%). In 2 a similar lanthanide binding is found, and the analysis of the LIS allows both the deduction of the molecular conformation (C‐2‐methyl equatorial, C‐2‐phenyl axial) and also the orientation of the phenyl group (perpendicular).
Unambiguous structure determination of some pyrazolo [1,5‐a]pyrimidine derivatives by multinuclear NMR spectroscopy
Authors: Chimichi Stefano , Cosimelli Barbara , Bruni Fabrizio , Selleri Silvia 
Published: May 2005

AbstractThe condensation of 3(5)‐aminopyrazole and 5‐amino‐3‐phenylpyrazole with ethyl 2,4‐dioxopentanoate and 2‐ethoxymethylidene‐3‐oxobutyrate has been re‐investigated. Contrary to previos reports, the former reaction gives rise to both regioisomeric pyrazolo [1,5‐a]pyrimidines (5‐carbethoxy‐7‐methyl‐and 7‐carbethoxy‐5‐methyl‐), the structures of which were determined by 1H and 13C NMR spectroscopy. The 6‐carbethoxy‐7‐methyl‐regioisomer is shown to be the only product in the reaction of the same aminopyrazoles with 2‐ethoxymethylidene‐3‐oxobutyrate; the regiochemical assignment was independently achieved by multimuclear (13C and 15N) NMR spectroscopy.
Characterization of aluminium complexes in tea extract. Part I—27Al NMR studies
Authors: Mhatre S. N. , Iyer R. K. , Moorthy P. N. 
Published: May 2005

AbstractThe high‐field 27Al NMR spectrum of aqueous tea extract contained two narrow resonances at 9.85 and 16.15 ppm. The spectra of aluminium chelates with a number of model ligands (catechol, pyrogallol, catechin, kojic acid, protocatechuic acid, ascorbic acid and salicylic acid) containing chelating moieties present in the constituents of tea showed broad resonances in the range 8–36 ppm. Potentiometric and NMR studies indicate the formation of a monohydroxo 1:1 Al‐catechin chelate (δ 8.3 ppm) with highly distorted symmetry. From a comparison of the NMR spectra of tea infusions at different pH values with those of aluminium chelates with malic acid and oxalic acid (minor constituents in tea), the resonance at 16.15 ppm was assigned to the highly symmetric octahedral anionic chelate trisoxalatoaluminium, [Al(C2O4)3]3−. This was confirmed by anion‐exchange separation of the chelate and its identification by 27Al NMR spectroscopy. The signal at 9.8 ppm could be due to a mixed ligand chelate containing oxalate. In the case of the aluminium‐malate system, the resonance at 20 ppm was assigned to a 1:2 chelate in which malate functions as a tridentate resulting in five‐ and six‐membered chelate rings.
NMR Study of isolobal N‐CH3+, N‐BH3 and N‐BF3 imidazole derivatives
Authors: Padilla‐Martínez Itzia Irene , Ariza‐Castolo Armando , Contreras Rosalinda 
Published: May 2005

AbstractSome N‐BH3, N‐BF3, N+‐CH3 and N+‐H imidazole derivatives have been prepared and their 13C, 11B and 1H NMR spectra studied. The effect of the different substituents was analysed. The isolobal character of the N‐BH3 and N‐CH3 derivatives is reflected in their spectra. In the 13CH coupled spectra of N‐borane adducts, the hydrides appear to be coupled with the heterocyclic carbon atoms. The C‐4 chemical shift value is indicative of the nature of the N‐substitution: lone pair (128–130 ppm), BH3 (126–128 ppm), BF3 and [CH3]+ (122–124 ppm) or [H]+ (117–119 ppm). The latter values allowed the chemical shifts of frozen imidazole to be estimated: 128 ppm for C‐4 and 117 for C‐5.
Carbon–carbon and proton–proton coupling constants in tetramethyl 9aH‐quinolizine‐1,2,3,4‐tetracarboxylate and its alkyl derivatives
Authors: Kamieńska‐Trela Krystyna , Kania Lidia , Bednarek Elżbieta 
Published: May 2005

AbstractThe 1H and 13C NMR spectra of the parent tetramethyl 9aH‐quinolizine‐1,2,3,4‐tetracarboxylate and 20 of its alkyl‐substituted derivatives were obtained and analysed. The study included measurements of one‐bond carbon–carbon and also proton–proton coupling constants across three, four, five and six bonds. An analysis of the data allowed an estimation of electron distribution and steric requirements in this group of compounds. No correlation was observed between 1J(C,C) values and the corresponding bond lengths.
1H NMR spectra of nitrated aminopyridines
Authors: Ritter Helmut , Kaiser M. 
Published: May 2005

AbstractThe 1H NMR spectra of 26 nitrated aminopyridines were measured and interpreted. Chemical shift assignments were based on existing chemical shift rules for substituted pyridines and spectral comparison with compounds of similar structure. Some o‐aminonitropyridines were found to give a splitting of the amino signals due to intermolecular hydrogen bonding; steric hindrance is shown to influence this bonding.
Carbon‐13 NMR spectra of bile acid derivatives. Part III. Unsaturated 5β‐cholanoic acids
Authors: Iida Takashi , Goto Junichi , Nambara Toshio 
Published: May 2005

Abstract13C NMR signals were assigned for 18 methyl 5β‐cholenoates with a double bond in ring A, B, C or D (Δ2, Δ3, Δ5, Δ6, Δ7, Δ8(14), Δ9(11), Δ11 or Δ14). The double bond substituent effects on the 13C NMR chemical shifts of the parent 5β‐cholanoates were clarified.
Investigation of solvation effects on the solid‐state 31P NMR spectra of tertiary phosphine derivatives and metal complexes
Authors: Davies Julian A. , Dutremez Sylvain G. 
Published: May 2005

AbstractAn investigation of bis(diphenylphosphino)methane dioxide (dppm dioxide), cis‐[PtCl2(PPh3)2] cis‐[PtCl2{P(p‐C6H4Cl)3}2] and cis‐[PtBr2(PPh3)2] by solid‐state CP/MAS 31P NMR spectroscopy, x‐ray powder diffraction and 1H, 13C{1H} and 31P{1H} solution NMR methods illustrates the sensitivity of the appearance of solid‐state NMR spectra to solvation effects in crystalline solids. The presence or absence of solvent of crystallization and the slow loss of solvent of crystallization from a sample over time are clearly manifested in the solid‐state NMR spectra as the local site symmetry in the solid is changed. These effects have led workers to report different data for a given compound when, in fact, different types of solvates were investigated.