bluuebunny/crossref_metadata_2025 huggingface dataset:
A carbon‐13 nuclear magnetic resonance spectral investigation of substituted triphenyl phosphates
Authors: Buchanan G. W. , Wightman R. H. , Malaiyandi M.
Published: May 2005

13C NMR chemical shifts and 13C31P couplings are reported for triphenyl phosphate and 13 alkyl derivatives. In ortho‐alkylated materials, it is found that the upfield γ shielding effect is only operative when the carbon atom, situated γ to the exocyclic oxygen, bears at least one hydrogen. Conformational changes about the arylO bond can be monitored via the vicinal 31pOC13C couplings.
Proton, carbon‐13 and fluorine‐19 NMR studies of N‐alkyl‐8‐fluoroquinolinium halides: Relative signs of through‐space 1H19F and 13C19F coupling constants
Authors: Barfield M. , Walter S. R. , Clark K. A. , Gribble G. W. , Haden K. W. , Kelly W. J. , Le Houllier C. S.
Published: May 2005

Because of experimental and theoretical interest in long‐range 1H19F and 13C19F coupling constants between proximate atoms, a series of N‐alkylfluoroquinolinium compounds was synthesized and the NMR parameters were accurately measured. By means of spin tickling and selective population inversion difference spectroscopy, the 5J(HF) and 4J(CF), which are associated with the proximate fluorine and methyl groups, were shown to be of the same (positive) sign as the directly bonded 13C1H and vicinal 1H1H coupling constants. In N‐methyl‐8‐fluoroquinolinium iodide (1a) and chloride (1b) 5J(HF)=+8.8 and 4J(CF)=+16.3 Hz, and in N‐ethyl‐8‐fluoroquinolinium iodide 5J(HF)=+3.0, 6J(HF)=+1.5, 4J(CF)=(+)15.8 and 5J(CF)=±5.2 Hz. Calculated molecular orbital results, which were based on the INDO‐FPT method and a molecular geometry from the x‐ray diffraction data for 1b, were in reasonable agreement with the 4J(CF) values, but the 5J(HF) values were of the wrong sign and magnitude.
EPR study of the alimemazine cation radical
Authors: López‐Rupérez F. , Conesa J. C. , Soria J.
Published: May 2005

The EPR spectrum of alimemazine cation radicals (ALMZ+) in a perchlorate single crystal has been studied at 293 K. Since strong exchange interactions between the radicals did not allow the determination of the hyperfine splitting constants, the spectrum of an ALMZ+ solution, frozen at 77 K, was also studied. The results, checked by computer simulation, indicate orthorhombic symmetry of the g(2.0075, 2.0059, 2.0023) and hfs (A=3.6G; A=2.0G; A=15.6G) tensors.
17O and 14N spectroscopy of 17O‐labeled nucleic acid bases
Authors: Burgar Matija I. , Dhawan Devindra , Fiat Daniel
Published: May 2005

Oxygen‐17 and nitrogen‐14 nuclear magnetic resonance techniques have been utilized in studying liquid‐state hydrogen bonding interactions between nucleic acid bases and between the bases and solvent. The bases uracil and thymine have been labeled with 17O at positions 2 and 4, cytosine at position 2 and thymine riboside at position 4. The 17O chemical shift was found to be a sensitive structural probe and to provide information concerning the resonance forms that contribute to the total wave function. The chemical shift of the oxygen of thymine and uracil at position 2 was detected at a higher field than that of oxygen at position 4, presumably owing to an increased contribution of single bonded‐oxygen valence bond structures at position 2. The 17O and 14N chemical shifts of cytosine were found to be strongly pH dependent, and the results have been interpreted in terms of predominant cytosine resonance structures contributing to the aqueous cation and anion. The 17O line width of cytosine in aqueous solution indicates the presence of hydrogen bonded dimers between neutral and cationic forms.
Solvent‐induced isotope effects in NMR spectroscopy. A study of hydrogen bonding between the carbonyl group in chalcone and trifluoracetic acid (TFA‐d or TFA) in chloroform solution
Authors: Kozerski Lech
Published: May 2005

Splittings, δi, were observed for each carbon atom, Ci, of chalcone in spectra obtained from coaxial 5 and 10 mm NMR sample tubes containing solutions equimolar in the concentration of the ketone and of TFA or TFA‐d as hydrogen‐bond donors, respectively. It was found that a linear expression, δi = (K–1)xHΔi+xDδi(D, H) relates these splittings, δi, induced by the isotopic substitution in a hydrogen bond, to the parameter Δi, denoting the change in chemical shift for each carbon site in complexed and free ketone, and δi(D, H), the solvent‐induced isotope effect in a complex. The origin of the phenomenon is briefly discussed. It is also shown that the secondary deuterium isotope effect can give the same information about the form of the potential energy well in the hydrogen‐bond as the primary H/D isotopte shifts.
Substituent parameters v. Lanthanide‐induced shifts in the interpretation of the 13C nuclear magnetic resonance spectrum of 5,5‐dimethyl‐2‐norbornanone
Authors: Yates Peter , Cong Dong Dao
Published: May 2005

Earlier assignments of 13C NMR signals to C‐6 and C‐7 in 5,5‐dimethyl‐2‐norbornanone (1) based on lanthanide‐induced shifts are interchanged on the basis of studies of deuterium‐labeled derivatives of 1. The revised assignments are in accord with predictions based on substituent parameters.
A statistical study of the additivity of substituent effects on the 5J(HH) long‐range coupling constant of the formyl proton in substituted benzaldehydes
Authors: Kolehmainen E. , Knuutinen J. , Salovaara P. J.
Published: May 2005

The additivity of chloro and hydroxy substituent effects on the formyl proton spin‐spin coupling constants with the meta ring proton, 5J(HH), has been tested with 15 chlorinated benzaldehydes and hydroxybenzaldehydes by multiple linear regression analysis. No general additivity rule was detected with whole data. Using benzaldehyde as the reference substance, a good correlation was achieved for p‐hydroxybenzaldehydes. The same reference compound was not suitable for o‐hydroxy derivatives; a much better correlation was observed using o‐hydroxybenzaldehyde as a reference compound in the latter case.
Effect of the internal reference on ASIS correlations: 3—Intrinsic ASIS of formyl protons
Authors: Bertrán J. Fernández , Rodríguez M.
Published: May 2005

The intrinsic ASIS of formyl protons in p‐X‐benzaldehydes, dimethylformamide and diphenylformamide in a series of aromatic hydrocarbon solvents have been calculated. These values of Δ¯xα of the formyl protons present excellent correlations in aromatic hydrocarbon solvents, and are factorizable into solute and solvent factors Ux and Vα, respectively. The Ux values are linearly related to the value of σp of the substituent in the solute. The Vα values depend on the substitution pattern of the benzene ring of the solvent molecules.
31P nuclear magnetic resonance titrations: Simultaneous evaluation of all pH‐dependent resonance signals
Authors: Lachmann Heinrich , Schnackerz Klaus D.
Published: May 2005

The simultaneous evaluation of ali pH‐dependent resonance signals (or multiplets) of an NMR titration offers a substantially increased accuracy and significance. The number of linearly independent titration equilibria is determined by graphical matrix rank analysis. The chemical shifts of all pH‐dependent resonance lines are plotted against each other (chemical shift or CS diagrams) indicating whether a single or more titration equilibria are NMR spectrometrically observable and how far they overlap with each other. An iterative curve‐fitting program allowing the simultaneous evaluation of all (pH) curves is available, from which pK values and chemical shifts of all species can be calculated. The starting pK values for the iteration need only be estimated very approximately (accuracy ±1–2 units). The titration end‐points do not have to be experimentally accessible. The different methods for the simultaneous evaluation of all pH‐dependent NMR signals are exemplified in the 31P NMR titration of thiamine pyrophosphate. In this case either the observed resonance lines (two doublets in a broad band proton decoupled spectrum) or the calculated chemical shifts for this AB system can be evaluated. A titration of sodium pyrophosphate was performed and evaluated for comparison.
Carbon‐13 NMR data for 1‐ and 2‐naphthyltrimethylstannanes and 9‐phenanthryltrimethylstannane
Authors: Schaeffer C. D. , Lefferts J. L. , Zuckerman J. J.
Published: May 2005

Carbon‐13NMR data recorded in the pulsed Fourier transform mode are re‐ ported for 1‐ and 2‐naphthyltrimethyl‐ stannanes and 9‐phenanthryltrimethyl‐ stannane. Assignments of ring carbon resonances are based on magnitudes of tin‐carbon spin‐spin coupling constants, substituent chemical shifts, spin‐lattice relaxation times and proton coupled spectra.
13C and 15N NMR spectra of 4‐substituted‐1‐dimethylphosphonopiperazines
Authors: Buchanan G. W. , Preusser S. H.
Published: May 2005

13C and 15N NMR chemical shifts and 13C‐31P and 15N‐31P coupling contants are reported for a series of ten 4‐substituted‐1‐dimethylphosphonopiperazines.
13C and 15N spin–lattice relaxation and chemical shift studies of pentane‐2,4‐diamine
Authors: Yu Chin , Levy George C.
Published: May 2005

13C and 15N NMR chemical shift and spin–lattice relaxation data have been measured for both meso‐ and racemic‐pentane‐2,4‐diamine. At high pH (12), relaxation is consistent with hindered rotation of the NH2 group due, in part, to the formation of intramolecular hydrogen bonds. At low pH (2), relaxation is consistent with relatively unhindered rotation of the NH3+ group. Rotational jump rates and barriers are reported, determined from the NT1 ratios between 15N and 13C nuclei. In all cases, the ratios for the racemic diastereomer are higher than those of the meso compounds; this is interpreted in terms of conformationally more stable intramolecular hydrogen bond formation in the meso compound. Chemical shifts for the diastereomeric amines show that 15N shifts move downfield on protonation along with methyl and methylene carbons, while the methine carbon resonances move upfield.
A 13C and 1H NMR study of the geometries of the 1,3‐dicyanoallyl anion: Thermal and photochemical interconversion
Authors: Boate D. R. , Hunter D. H.
Published: May 2005

Glutacononitrile (1,3‐dicyanopropene) (2) was converted to its anion (1) by treatment with sodium hydride in tetrahydrofuran. Both 13C and 1 NMR showed that the sodium salt of 1 in THF existed in three slowly interconverting geometries (U, W and S). These geometries were present in similar amounts but the relative amounts of each proved to be concentration dependent. Irradiation of a 0.01 M solution of 1 at −80°C led to the conversion of a mixture of the U, W and S forms of 1 to only the W and S forms. Upon warming to 0°C equilibrium was re‐established with a half‐life of approximately 8 h.
Conformational investigations of cyclic dipeptides: Cyclo‐glycyl‐L‐methionyl, cyclo‐glycyl‐D,L‐norleucyl and cyclo‐glycyl‐D,L‐norvalyl
Authors: Siemion I. Z. , Picur B.
Published: May 2005

The E0 rotamer of c‐Gly‐Met has been found to be almost as equally populated as the F rotamer at low temperatures, whereas in c‐Gly‐D,L‐Nle and c‐Gly‐D,L‐Nvl the F rotamer predominates. The increase of the E0 rotamer population parallels the increase of the boat diketopiperazine (DKP) ring conformation, in which Med side‐chain occupies a pseudoaxial position. Thermodynamic parameters for DKP ring inversion and for conformational transitions in the side‐chains were experimentally determined for each cyclic dipeptide investigated.
The rα structures of propyne oriented in two different liquid crystals
Authors: Dombi G. , Diehl P.
Published: May 2005

The 1H spectra with natural abundance 13C satellites of propyne partially oriented in the liquid crystals ZLI 1167 and Merck Phase IV were analysed and molecular structures determined from the direct couplings corrected for harmonic vibrations. The resulting internuclear distance ratios and angles agree with microwave data and the solvent effects are small, i.e. of the order of 1% and 0.5° in the methyl group, and 2% in the acetylenic moiety.
A proton spin–lattice relaxation rate and nuclear Overhauser effect investigation of the stereochemistry of some 1‐aryl derivatives of 1,2‐dihydro‐s‐triazines
Authors: Peiris Sriyawathie , Colebrook Lawrence D.
Published: May 2005

Proton spin–lattice relaxation rates (R1 values) have been measured, at 400 MHz, for a number of 2‐methyl‐ and 2,2‐dimethyl‐substituted 4,6‐diamino‐1‐aryl‐1,2‐dihydro‐S‐triazines. These compounds have high barriers to internal rotation about the aryl CN bond, and exist in solution as mixtures of enantiomeric or diastereomeric rotational isomers. Diastereotopically related 2‐methyl groups in enantiomeric rotamers, and 2‐methyl and 2‐methine protons in diastereomeric rotamers, typically have different relaxation rates. In favourable circumstances this information may be used to identify the individual rotamers. Unequivocal direct identification of rotamers may be obtained from nuclear Overhauser effect difference spectra.
Unusual deuterium isotope effects in 13C NMR spectra of trans‐stilbene
Authors: Meić Ziatko , Vikić‐topić Dražen , Güsten Hans
Published: May 2005

A detailed analysis of the 13C NMR spectra of trans‐stilbene and ten deuteriated trans‐stilbenes has been undertaken. Some unusual deuterium isotope effects on carbon–hydrogen spin–spin coupling constants could not be explained by the ordinary primary and secondary isotope effects. The positive and negative changes of nJ(CH) were interpreted in terms of a steric effect, the vibrational influence of the CD bond and the para‐effect induced by deuterium. In this respect, deuterium behaves as a real substituent with electronic properties different from those of hydrogen. The deuterium isotope effects on 13C NMR chemical shifts and carbon–deuterium coupling constants have also been determined.
Quaternary suppression via difference spectroscopy for 13C CP/MAR of organic solids: Application to a phenylazonaphthol
Authors: Harris Robin K. , Jonsen Paul , Packer Kenneth J.
Published: May 2005

A pulse sequence for obtaining solid‐state NMR spectra of proton‐bearing 13C nuclei only, based on a difference method, is proposed. As an example, spectra of the dyestuff CI Pigment Red 57:1 [monohydrated calcium salt of 1‐(2‐sulpho‐4‐methylphenylazo)‐2‐hydroxnaphthyalene 3‐carboxylic acid] are illustrated. The difference method reveals a peak which is otherwise severely overlapped by others. Its presence is confirmed by higher field spectra. The results show that the dyestuff is present as the keto‐hydrazo tautomer.
Carbon‐13 chemical shift assignment of E‐Hydroxyazastilbenes
Authors: Wyrzykiewicz Elżbieta , Lpucha Andrzej , Sylwestrzak Urszula
Published: May 2005

The 13C NMR spectra of nine isomeric E‐hydroxyazastilbenes (E‐hydroxystyrylpyridines) have been fully assigned. The Ai and AiK empirical parameters of o‐(m or p‐)hydroxystyryl and 2‐(3‐ or 4‐)vinylpyridyl groups for the prediction, of chemical shifts of substituted styrylpyridines were calculated.
13C NMR spectral data for some N,N‐dialkylbenzylamines and their cyclopalladated complexes
Authors: Barr Neal , Dyke Stanley F. , Frost R. L. W.
Published: May 2005

13C NMR data for some N,N‐dialkylbenzylamines and their chloro‐(N,N‐dialkylbenzylamine‐6,C,N)‐tri‐phenylphosphinepalladium(II) complexes are presented and simple shift parameters defined.
Multinuclear NMR spectra of (CH3)3SnCH2M(CH3)3 (MSn, Ge, Si, C) and some halogenated derivatives
Authors: Hawker Darryl W. , Wells Peter R.
Published: May 2005

Chemical shift and scalar coupling constant information has been obtained from the 1H, 13C, 29Si and 119Sn NMR spectra of a series of compounds (CH3)3SnCH2M(CH3)3, where M = Sn, Ge, Si or C and with one or two CH3(Sn) groups replaced by Cl, Br or I. The (CH3)3M and (CH3)3MCH2 groups appear to have opposite substituent effects on chemical shifts.
Aromatic chemical shifts in ar‐hydroxy‐ and ‐methoxy‐substituted indole alkaloids; reference data and substituent‐induced chemical shifts for ten different chromophoric groups
Authors: Verpoorte R. , van Beek T. A. , Riegman R. L. M. , Hylands P. J. , Bisset N. G.
Published: May 2005

On the basis of available 13C NMR spectral data for indole alkaloids, substituent‐induced chemical shifts have been calculated for various types of ar‐hydroxy‐ and ‐methoxy‐substituted indole alkaloids.
Investigation of intracellular phosphate pools of the green alga Chlorella using 31P nuclear magnetic resonance
Authors: Sianoudis J. , Mayer A. , Leibfritz D.
Published: May 2005

31P NMR measurements were performed in order to study the intracellular phosphate pools of the green alga Chlorella fusca. Cells of asynchronous cultures contain a large pool of polyphosphates, whereas the amount of polyphosphates in cells of synchronous cultures depends on the state of differentiation. The assignment of extracellular and intracellular inorganic orthophosphate is achieved by changing the pH, whereas the intracellular compartmentation of inorganic orthophosphates and sugar phosphates is shown during irradiation of the cells with light within the NMR spectrometer.
Multinuclear magnetic resonance study of organomercury fulminates. The structure of mercury fulminate in solution
Authors: De Sarlo Francesco , Brandi Alberto , Fabrizi Lino , Guarna Antonio , Niccolai Neri
Published: May 2005

1H, 13C, 14N and 199Hg NMR data were obtained for organomercury fulminates, RHgCNO (R  Me, Ph, CNO). The relatively slow relaxation processes effective for the quadrupolar nitrogen muclei of these compounds allow the detection of 199Hg14N scalar coupling constants. This feature is ascribed to the presence of low electric field gradients around the 14N nucleus, owing to the presence of the mercury atom. In mercury fulminate, the 199Hg nucleus appears to be coupled with two equivalent 14N nuclei, thus indicating the existence of a covalent structure Hg(CNO)2 in solution.
Theoretical additivity in multipath 13C, 1H coupling constants
Authors: Contreras R. H. , Scuseria G. E.
Published: May 2005

Different path contributions to the Fermi contact term of carbon‐hydrogen coupling constants in several bicycloalkanes were calculated using the ‘inner projections of the polarization propagator’ (IPPP) approach. The ground‐state wave functions were calculated at the INDO level of approximation. Three and four‐bond contributions to the couplings, and the through‐space transmission via the rear lobes of the CX (X  H, F) bonds attached to the bridgehead carbon atoms, were calculated. The additivity of these contributions compared with the total INDO couplings is good. Similar paths in different molecules give dissimilar contributions to the couplings.
Compounds with bridgehead nitrogen. 48—stereochemistry of the 5‐methylperhydropyrido[3,2,1‐i,j][3,1]‐benzoxazines
Authors: Crabb Trevor A. , Jupp Philip A. , Turner Christopher H.
Published: May 2005

Six of the eight possible diastereoisomeric 5‐methylperhydropyrido[3,2,1‐i,j][3,1]benzoxazines have been synthesized, and the utility of the C‐3 methylene proton NMR parameters [J(3ax3eq) and Δ3ax3eq] in the assignment of configurations has been demonstrated.
Conformational study of methyl esters of some aliphatic erythro‐ and threo‐dichlorocarboxylic acids
Authors: Pitkänen Maija
Published: May 2005

The average conformations of methyl esters of some aliphatic erythro‐ and threo‐dichlorocarboxylic acids in dilute carbon tetrachloride solutions have been determined from the vicinal proton–proton coupling constants and 1H NMR shifts. The 13C shift differences between the erythro and threo forms are compared and discussed with regard to the differences in the average conformations.
Preferred conformations of pilocarpine, pilocarpine.HCl and isopilocarpine.HCl in solution, deduced from 200 MHz 1H NMR spectra
Authors: Maat L. , Peters J. A. , Aboul‐Enein Hassan Y.
Published: May 2005

The 200 MHz 1H NMR spectra of pilocarpine, pilocarpine.HCl and isopilocarpine.HCl have been studied. Evidence is presented for the preferred conformations of the compounds in aqueous solution, with the methylimidazolyl moiety antiperiplanar with respect to the α‐carbon of the butanolide ring.
Complexation of hydroxylated ent‐kaurane diterpenoids with boric acid as an aid to the assignment of the 13C NMR spectra
Authors: Fernández‐Gadea Francisco , Jimeno María L. , Rodríguez Benjamín
Published: May 2005

The 13C NMR spectra of some hydroxylated ent‐kaurane diterpenoids were measured in CDCl3‐Py‐d5 (1:1) solution and also after addition of boric acid. Complexation of ent‐3β,18‐, ent‐7α,15β‐, ent‐7α,15α‐, ent‐15β,16β‐ and ent‐16β,17‐dihydroxy derivatives with boric acid produced considerable chemical shift changes and marked broadening of the signals of the hydroxy‐bearing and neighbouring carbon atoms. This behaviour provides a useful and reliable method for assigning the 13C NMR spectra of these compounds.
Electron spin resonance study of some polycyclic nitrogen heterocyclic radical anions
Authors: Sevenster Arjen J. L. , Tabner Brian J.
Published: May 2005

In dimethylformamide the ESR spectra of the radical anions of dibenzo[f,h]quinoxaline and dibenzo[a,c]phenazine both exhibit line broadening due to slow molecular tumbling over a wide temperature range. Similar effects are also observed in the spectra of the radical anions of quinoxaline and phenazine. The ESR spectra of the radical anions of dibenzo[f,h]quinoxaline and dibenzo[a,c]phenazine have been interpreted by computer reconstruction and the hyperfine splitting constants assigned with the aid of Hückel unpaired electron density calculations.
Configurations and conformations of cis‐ and trans‐N‐methyl‐ and ‐N‐benzyl‐4,5‐ and ‐5,6‐tetramethylenetetrahydro‐1,3‐oxazines
Authors: Sohár P. , Fülöp F. , Bernáth G.
Published: May 2005

The configurations and conformations of cis‐ and trans‐N‐methyl‐ and ‐N‐benzyl‐4,5‐ and ‐5,6‐tetramethylenetetrahydro‐1,3‐oxazines were determined by 1H and 13C NMR spectroscopy. The cis isomers are conformationally homogeneous, having the hetero atom attached to the cyclohexyl ring, in the axial and equatorial positions, respectively, in the 5,6‐ and 4,5‐tetramethylene compounds, similar to the case of the 2‐p‐nitrophenyl‐substituted analogues investigated previously.
Assignment of proton NMR spectra and conformational analysis by two‐dimensional heteronuclear relayed correlation NMR spectroscopy
Authors: Turner Christopher J.
Published: May 2005

The method of two‐dimensional heteronuclear relayed correlation spectroscopy was used to establish the assignment of the severely overcrowded part of the proton spectrum of menthol by relating it to the previously assigned carbon spectrum. Extrapolation of the signal‐to‐noise ratio obtained with overnight data accumulation on a 10 mM solution suggests that this experiment should be feasible on as little as 10 mg of a moderate‐sized organic compound.
1H and 13C NMR studies on N‐(cyclohex‐2‐en‐1‐ylidene)amines
Authors: Kilger Ralf , Margaretha Paul
Published: May 2005

1H and 13C NMR spectroscopy allow the identification of diastereomeric Z‐ and E‐N‐(cyclohex‐2‐en‐l‐ylidene)amines and the assignment of their configuration.
Solvent dependence of the molecular structure of hydrogen cyanide determined by NMR of partially oriented molecules
Authors: Dombi G. , Diehl P. , Lounila J. , Wasser R.
Published: May 2005

The chemical shifts and the direct and indirect spin–spin coupling constants of HCN have been measured in various liquid crystal solvents. The sign of the indirect coupling constant J(15NH) is found to be negative. The 13C shift anisotropy is 334±20 ppm. The molecular structure apparently varies considerably with the solvent used. These solvent effects, which can be attributed to a correlation between vibration and rotation of the molecule, are corrected.
A carbon‐13 nuclear magnetic resonance study of the 1,4‐diene analogues of steroid hormones and related steroids
Authors: Gonzalez Mario D. , Burton Gerardo
Published: May 2005

The 13C NMR spectra of sixteen 4‐ene‐3‐keto‐ and 1,4‐diene‐3‐keto corticosteroids are described. Substituent shifts and the effect of added methanol‐d4 are reported, and conformational distortions and intramolecular hydrogen bonding are analysed based on these data.
Large lanthanide‐induced chemical shifts in cobalt complexes of enethials (α,β‐unsaturated thioaldehydes)
Authors: Dittmer Donald C. , Parker Edward Joseph , Bodwell James R.
Published: May 2005

Eu(fod)3‐, Yb(fod)3‐ and Pr(fod)3‐induced chemical shifts of the ‘thioaldehydic’ protons in enethial ligands complexed to a cobalt cyclopentadienyl group are unusually large and in the same direction (10–30 ppm downfield per mole of shift reagent per mole of substrate). The shifts of the protons induced by Eu(fod)3 and Pr(fod)3 in the enethial ligands show an alternation in sign on proceeding away from the sulfur atom. In contrast to the results with the fod reagents, the ytterbium and lanthanum shift reagents Yb(thd)3 and La(thd)3 caused only small shifts of protons in the 2‐phenylpropenethial ligand. No induced shifts with the Eu or Pr reagents were observed for a cyclopentadienyl cobalt complex of dithioglyoxal. The induced shifts in these enethial complexes may be caused by varying blends of complex formation, contact and pseudocontact shifts. Caution is advised in assigning origins to lanthanide induced shifts in such organometallic systems.
The conformational energy difference for δ‐valerolactone
Authors: Lambert Joseph B. , TeVrucht Mollie L. E.
Published: May 2005

The temperatuure dependence of the vicinal OCH2CH2 coupling constant in the six‐membered ring δ‐valerolactone suggests the presence of at least two conformers of unequal energy. Analysis of this temperature dependence by the Wood‐Fickett‐Kirkwood method in six solvents produces free energy differences in the narrow range 0.8–1.4 kcal mol−1, with a mean of 1.0 kcal mol−1 and no apparent dependence on solvent polarity. Thus the two conformers, probably the half‐chair and the classic boat, have similar polarities. The analogous four‐ and five‐membered lactones show little or no temperature dependence for their analogous coupling constants, in agreement with the presence of a single conformation for these rings.
1H and 13C NMR study of phosphopeptides: 2—Ac–PSer–Gly, Ala–PSer–Gly and Gly–PSer–Phe
Authors: Pogliani L. , Ziessow D.
Published: May 2005

1H and 13C NMR spectra of AC–PSer–Gly, Ala–PSer–Gly and Gly–PSer–Phe have been measured and analysed as a function of pD. The NMR parameters of the PSeryl side chain are a function of the sequence. The second titration step of the phosphate group (pK2 = 5.7) is much more difficult to detect in Ac–PSer–Gly and Ala–PSer–Gly than in Gly–PSer–Phe. The conformation in which H‐αC‐αC‐βOP forms a planar W‐type arrangement predominates only for Ala–PSer–Gly. In the other two phosphopeptides the gauche conformations contribute increasingly, in particular for Gly–PSer–Phe.
Proximity effect in the 13C NMR spectra of alkylpyridines: An aid in structure elucidation
Authors: Holík Miroslav , Turečková Milena , Vymětal Jan
Published: May 2005

The structures of seven polysubstituted alkylpyridines, recently isolated from coal tar, were elucidated using their 13C NMR spectra. For tri‐ and tetra‐substituted derivatives the correct isomeric structure was found from their conformity with the proximity effect, i.e. the deviations from additivity when calculating chemical shifts from substituent increments (SCS) for sterically crowded molecules. This effect manifests itself both on the ring and on the alkyl carbon signals, and in most cases shifts their position upfield.
Reversal of order of chemical shifts. Differential solvent effects in the hydrogen shifts of toluene, m‐xylene and o‐xylene as determined by 320 MHz tritium NMR spectroscopy
Authors: Long Mervyn A. , Saunders John K. , Williams Philip G. , Odell Allan L. , Martin R. Wayne
Published: May 2005

Chemical shifts for the aromatic tritons of toluene decrease in the order meta>para>ortho for pure toluene, but in the order meta>ortho>para for dilute solutions of toluene in carbon tetrachloride, chloroform, cyclohexane and dimethyl sulphoxide; m‐xylene shifts are 5>4,6>2 in the pure state and 5>2>4,6 in carbon tetrachloride and dimethyl sulphoxide; o‐xylene shifts are 4,5>3,6 in the pure state and reversed in carbon tetrachloride.
A natural abundance 15N NMR investigation of bilirubin IX‐α
Authors: Hansen Poul E. , Jakobsen Hans J.
Published: May 2005

Natural abundance 15N NMR spectra have been obtained for bilirubin IX‐α using polarization transfer via the INEPT and SINEPT‐2 techniques. The resonances for all four nitrogens are clearly resolved. 15N chemical shifts and 15N1H coupling constants over one and three bonds are reported. Heteronuclear chemical shift correlation between 15N and 1H for the four NH groups has been established by means of the SINEPT‐2 pulse sequence.
The use of two nematic solvents in the determination of molecular structure of systems providing deceptively simple spectra
Authors: Khetrapal C. L. , Kunwar A. C. , Arumugam S.
Published: May 2005

The use of two liquid crystals as solvents in the determination of molecular structure has been demonstrated for systems which do not provide structural information from studies in a single solvent owing to the fact that the spectra are deceptively simple, with the result that all the spectral parameters cannot be derived with reasonable precision. The specific system studied was 2‐(p‐bromophenyl)‐4,6‐dichloropyrimidine, for which relative inter‐proton discances have been determined from the proton NMR spectra in two nematic solvents.
Configurational analysis of diastereomeric open‐chain and cyclic nitro‐substituted diols by NMR spectroscopy
Authors: Sohár P. , Mikite Gy. , Pelczer I. , Kovács Á. , Kis‐Tamás A.
Published: May 2005

Nitro‐substituted 1,3‐dioxanes and pyrans with potential biological activity were synthesized. The relative configurations of the threo and erythro isomers of 2‐nitro‐1‐phenylpropane‐1,3‐diol (the starting materials) and of 5‐nitro‐2,4‐diphenyl‐1,3‐dioxane, the products formed with benzaldehyde, were determined by 1H and 13C NMR spectroscopy. Cinnamaldehyde and nitroethanol give a homologue of nitrophenylpropanediol, which exists as a mixture of two diastereomeric cyclic hemiacetals. After dissolving in CDCl3, the ratio of these components changes from approximately 10:1 to 3:2 in a few days. The ethyl acetal of the hemiacetal is stereohomogeneous, and the ethoxy group is axial to the pyran ring owing to the anomeric effect. This configuration was proved by two‐dimensional NMR measurement, permitting separate observation of the originally overlapping multiplets and direct reading of the H,H coupling constants.
13C NMR studies on trifluoroacetyl derivatives of 2‐acetamido‐2‐deoxyhexoses
Authors: Ranganathan M. , Balaram P.
Published: May 2005

The effect of trifluoroacetylation on the 13C chemical shifts of 2‐acetamido‐2‐deoxyhexoses was examined. Studies of the 2‐acetamido derivatives of glucose, galactose and mannose established that no regular trend in the 13C shifts occurred on trifluoroacetylation. This was in marked contrast to the results obtained for the 1H chemical shifts.
Substituent dependence of stable conformations in triazolobenzothiazines
Authors: Sohár P. , Fodor L. , Szabó J. , Bernáth G.
Published: May 2005

From the 1H and 13C NMR spectra of angularly condensed triazolobenzothiazine derivatives it was established that these compounds can be classified into two conformation types, depending on the substituents. The 10‐methyl‐3‐carbethoxy derivatives are cis‐anellated, conformationally flexible systems, where one of the aromatic hydrogens (H‐9) and one of the methoxy substituents (8‐OMe) of the benzothiazine skeleton on the one hand, and the 1‐aryl ring on the other, lie close to each other in the preferred conformer. By assuming this conformation, the molecules avoid the steric hindrance of the 10‐Me and 1‐aryl groups. All compounds unsubstituted on the angular C‐10 atom, and the 3‐aryl‐substituted derivatives of the 10‐Me analogues, occur in a different conformation, containing the 1‐aryl ring well removed from H‐9 and the 8‐OMe group.
Nitrogen‐15 nuclear magnetic resonance spectroscopy as a probe for the study of membrane models
Authors: Tellier Charles , Malnoe Patricia , Poignant Serge
Published: May 2005

15N NMR spectroscopy has been used to investigate liposomes from an enriched phospholipid (dipalmitoyl‐phosphatidylcholine). It is shown that this probe can yield interesting information on the dynamics of head groups and on some interactions at the lipid–water interface. Even large multilamellar vesicles give rise to narrow, symmetrical signals, with a maximum nuclear Overhauser effect over the phase transition temperature. The sensitivity of the technique as regards structural changes was demonstrated by a complete study made between 20 and 60°C.
17O NMR studies on polycyclic quinones, hydroxyquinones and related cyclic ketones: Models for anthracycline intercalators
Authors: Chandrasekaran Subramanian , Wilson W. David , Boykin David W.
Published: May 2005

The 17O chemical shifts for six cyclic ketones which serve as models for quinones, viz. cyclohex‐2‐enone (1), α‐tetralone (2), anthrone (3), 4H‐pyran‐4‐one (4), 1‐benzopyran‐4(4H)‐one (5), xanth‐9‐enone (6), and for six quinones, viz. benzoquinone, naphthoquinone, anthraquinone, 2,5‐dihydroxybenzoquinone 5,8‐dihydroxynaphthoquinone and 1,4‐dihydroxyanthraquinone, were measured in toluene at 90°C. A shielding effect of approximately 50 ppm per fused benzene ring was noted for the quinones and related carbocyclic ketones; however, the analogous series of heterocyclic fused ring ketones 4–6 showed only a slight fused‐ring effect on the carbonyl chemical shift. A single 17O resonance was observed for 2,5‐dihydroxybenzoquinone (358 ppm) and 5,8‐dihydroxynaphthoquinone (283 ppm), indicating rapid proton exchange between the oxygen atoms of these compounds. However, 1,4‐dihydroxyanthraquinone gave two discrete 17O signals at 441 and 87 ppm, indicating that in this case proton exchange between oxygen atoms is slow.
Conformational studies of dicyclohexylthallium chloride, bis(4‐methylcyclohexyl)thallium chloride and bis(4‐tert‐butylcyclohexyl)thallium chloride by 1H NMR
Authors: Cheesman Bruce Victor , White Raymond Frederick Martin
Published: May 2005

Vicinal thallium–hydrogen coupling constants are used to discuss conformations in dicyclohexylthallium chloride, bis(4‐methylcyclohexyl)thallium chloride and bis(4‐tert‐butylcyclohexyl)thallium chloride. Thallium does not have a very strong preference for equatorial positions in dicyclohexylthallium chloride, whereas bis(4‐alkylcyclohexyl)thallium chlorides exist largely in one conformation. Bis(4‐methylcyclohexyl)thallium chloride exists in three isomeric forms; the major product appears to be the cis‐isomer (equatorial methyl, axial thallium), with the other two isomers probably containing thallium trans to the methyl group (axial thallium being preferred). The preference for the cis‐isomer (equatorial tert‐butyl, axial thallium) of bis(4‐tert‐butylcyclohexyl)thallium chloride is such that other isomers are not obtained.
Application of 1H and 13C NMR to the structural elucidation of tetrahydroquinoxalines condensed with five‐membered heterocycles
Authors: Charushin V. N. , Chernyshev A. I. , Sorokin N. N. , Chupakhin O. N.
Published: May 2005

1H and 13C NMR spectral data for 21 N‐methyltetrahydroquinoxalines annelated with furan, pyrrole, imidazole or thiazole rings are reported. Unambiguous assignments of the ring junction 13C resonances were made on the basis of selective decoupling experiments and with the aid of one‐bond and long‐range 13C–1H coupling constants. The effects of five‐membered heterocycles on the 1H and 13C chemical shifts of the ring junction hydrogen and carbon atoms are considered. Values of one‐bond 1J(CH) and vicinal 3J(HH) coupling constants between the ring junction protons are also discussed as a diagnostic means for structural elucidation of tetrahydroquinoxalines condensed with five‐membered heterocycles.
Unusually large deuterium isotope effects on one‐bond 13C, 1H coupling constants in trans‐stilbene challenged
Authors: Ernst Ludger
Published: May 2005

The reported apparent large decrease in 1J(C‐α, H‐α) by 1.75±0.20 Hz on replacement of one of the olefinic protons by deuterium in trans‐stilbene is due to improper first‐order analysis of the 1H‐coupled 13C spectrum of the parent compound. Consequently, the implied conformational difference between trans‐stilbene and α‐deuterio‐trans‐stilbene, which was used to explain the result, is not substantiated.
13C NMR spectra of some N‐substituted 1,2‐dihydro‐3,1‐benzoxazin‐4‐ones
Authors: Aversa Maria C. , Ferlazzo Alida , Giannetto Placido
Published: May 2005

The natural abundance 13C NMR spectra of a series of hitherto unknown l‐atyl‐methyl‐1,2‐dihydro‐3,1‐benzoxazin‐4‐ones have been recorded. The assignments of the various resonances have been made from chemical shift arguments, by the analysis of the fine splittings caused by one‐bond and long‐range couplings and also by comparison with model compounds.
The effect of the internal reference on ASIS correlations: 1—Formyl protons of p‐X‐benzaldehydes
Authors: Bertrán J. Fernández , Rodríguez Mario
Published: May 2005

The correlation of the ASIS of the formyl protons of benzaldehyde and six of its p‐X‐derivatives in 12 aromatic solvents show marked deviations. Evidence is presented that these deviations are caused by variations in the shielding of the internal reference protons caused by aromatic solvents. Equations are developed which gauge the effect of TMS on the linear correlations of proton ASIS.
Studies of Erythrina alkaloids: VII—13C NMR spectral studies of some Erythina alkaloids
Authors: Chawla A. S. , Chunchatprasert S. , Jackson A. H.
Published: May 2005

A variety of alkaloids have been isolated from the seeds of a range of Erythrina species, including dienoid, alkenoid and lactonic derivatives. The 13C NMR spectra of these compounds have been assigned by internal comparisons within this series of related compounds and also by the use of model compounds.
Application of the INEPT technique to 13C NMR assignments in polynuclear aromatic nitrogeneous heterocycles; 6H‐pyrido[4,3‐b]‐5,11‐dimethylcarbazole (ellipticine)
Authors: Mansour T. S. , Wong T. C. , Kaiser E. M.
Published: May 2005

The 13C NMR spectrum of 6H‐pyrido[4,3‐b]‐5,11‐dimethylcarbazole has been re‐examined to confirm the assignments using normal decoupled and coupled INEPT techniques. The results indicate that there were several errors in previous assignments. J(13C, 1H) for the seven methine carbons have also been obtained.
Carbon‐13 chemical shift assignment of some organophosphorus compounds: 1—Dialkyl and diaryl (alkylamido)phosphates with general formula Y2P(X)NHR
Authors: Al‐Rawi Jasim M. A. , Behnam George Q. , Ayed Naceur
Published: May 2005

Carbon‐13 chemical shifts and the POC, POCC, PNC and PNCC coupling constants of 18 compounds containing the amine moiety, and with the general formula Y2P(X)NHR [Y=C2H5O, C6H5O, CH2O, Y2=1,2‐dioxybenzene; X = O or S; R = H, CH3, C2H5, PhCH2CH2, (CH3)2CH, C(CH3)3, C6H11, C6H5, C6H5NH] have been determined. The Y2P(X) group shows a sterically induced effect on the amine moiety; the 13C chemical shift of the Y group is, however, almost unaffected on replacing P(O) by a P(S) group.
Chemistry of heterocycles 6—13C NMR study of 7,8‐dihydro‐6H‐3‐methyl‐5,7‐diarylisoxazolo‐[4,5‐B]azepines
Authors: Rao C. Jankiram , Krishnamurthy A. , Shoolery James N.
Published: May 2005

The 13C NMR data of six 7,8‐hydro‐6H‐3‐methyl‐5,7‐diarylisoxazolo[4,5‐b]‐azepines have been studied. The studies have been confirmed by a new technique called the ‘attached proton test’.
Stereochemistry of diastereoisomeric propionyl esters of 4‐(2‐furyl)‐3‐methyl‐1‐phenethyl‐piperidin‐4‐ols and the analgesic ether derived from their acid‐catalysed ethanolysis
Authors: Casy A. F. , Dewar G. H. , Pascoe R. A.
Published: May 2005

The stereochemistry of diastereoisomeric propionyl esters of 4‐(2‐furyl)‐3‐methyl‐1‐phenethylpiperidin‐4‐ols has been established by 13C NMR analysis. Both isomers, after acid‐catalysed ethanolysis, are converted to the corresponding 4‐ethoxy derivative of configuration (t‐3‐Me, r‐4‐OEt) that correlates with its analgesic properties.
NMR studies on aromatic compounds: VI—13C NMR spectra of some mono‐ and disulphonato‐substituted hydroxynaphthoic acids in DMSO‐d6–water solution
Authors: ruotsalainen heikki , lajunen marja , h. j. lajunen lauri
Published: May 2005

Carbon‐13 NMR spectra of sulphonatosubstituted hydroxynaphthoic acids were recorded with and without proton noise decoupling in DMSO‐d6–water (2:1 v/v). The 13C chemical shifts were assigned by using substituted naphthalenes as reference compounds. The additivity law of the substituent effects is discussed for the naphthalenesulphonic acids studied.
13C13C spin coupling constants in tetrahydronaphthylene, hexahydrobenzanthracene and benzo[a]pyrene derivatives
Authors: Cox Richard H. , Levy Louis A.
Published: May 2005

The 13C13C spin coupling constants have been determined in substituted [1‐13C]tetrahydronaphthylenes, [5‐13C]hexahydrobenzanthracenes and [5‐13C]benzanthracene. In addition, the 13C13C spin coupling constants for 7‐hydroxy[7‐13C]benzopyrene, trans‐7,8‐dihydro[7‐13C]benzopyrene‐7,8‐diol and trans‐7,8‐dihydro[10‐13C]benzopyrene‐7,8‐diol are reported, together with the one‐bond carbon‐carbon coupling constants between C‐4 and C‐5 in selected 4,5‐disubstituted benzopyrenes. Values for the directly bonded coupling constants and long‐range coupling constants are similar to those reported previously for other aromatic and aliphatic systems. Substituent effects on carbon‐carbon coupling are compared for similarly substituted cyclic and acyclic systems.
Enantiomeric excess determination of new classes of chiral sulphur compounds by the use of europium shift reagents
Authors: Annunziata R. , Cinquini M. , Cozzi F.
Published: May 2005

The enantiomeric composition of derivatives of new classes of optically active sulphur compounds (variously substituted sulphoxides, sulphoximes, sulphilimines) has been readily determined with the aid of chiral europium shift reagents.
NMR spin–lattice relaxation time measurements in organochalcogen compounds
Authors: Abel E. W. , Orrell K. G. , Platt A. W. G.
Published: May 2005

1H and 77Se spin‐lattice relaxation times have been measured for the series of organochalcogen compounds MeE(CH2)nEMe (E=S, Se, n=0–3; E = O, n = 1, 2). The methyl and methylene proton T1 values decreased with increasing mass/size of the chalcogen and with increasing methylene chain length. The values are primarily due to intra‐ and inter‐molecular dipole‐dipole relaxation with proton‐proton cross‐relaxation effects playing a significant role. 77Se T1 values are dominated by spin rotation and chemical shielding anisotropy mechanisms, their relative importance depending on the size of the molecule and temperature of measurement.
Low‐temperature 15N NMR spectra of reduced 1,3‐heterocyclic systems
Authors: Takeuchi Yoshito , Crabb Trevor A.
Published: May 2005

The 15N NMR spectra of the O‐inside cis‐fused conformer of perhydropyrido[1,2‐c][1,3]thiazine shows a shielding of the nitrogen of 23.0 ppm relative to the trans‐fused conformer. In contrast, 15N shifts for the cis‐and trans‐fused conformers of perhydro‐oxazolo[3,4‐a]pyridine and perhydrothiazolo[3,4‐a]pyridine show corresponding shieldings of only 0.6 and 2.5 ppm, respectively.
Carbon‐13 NMR spectra of several dicyclopentadiene derivatives
Authors: Dawson Brian A. , Stothers J. B.
Published: May 2005

The 13C shielding data for 69 derivatives of dicyclopentadiene are reported. These derivatives include compounds from both the exo and endo series having both saturated and unsaturated trimethylene bridges.
In vivo topical magnetic resonance
Authors: Shaw Derek
Published: May 2005

NMR is rapidly extending biochemistry into the in vivo situation. This review provides a survey of the instrumental techniques necessary for high resolution spectra to be produced from a whole animal. The current areas of application are then reviewed for phosphorus, 13C topical magnetic resonance etc., and finally the potential areas for future development are outlined.
Heterocycles: 2—Regiospecific addition of methylhydrazine to acetylenic ketones
Authors: El‐Rayyes N. R. , Hovakeemian G. H. , Hammoud H.
Published: May 2005

The reaction of 1‐p‐methoxyphenyl‐3‐phenyl‐2‐propen‐1‐one and 3‐p‐methoxyphenyl‐1‐phenyl‐2‐propen‐1‐one with methylhydrazine gave 1‐methyl‐3‐p‐methoxyphenyl‐5‐phenylpyrazoline and 1‐methyl‐3‐phenyl‐5‐p‐methoxyphenylpyrazoline, respectively. These compounds, on oxidation, gave 1‐methyl‐3‐p‐methoxyphenyl‐5‐phenylpyrazole(2) and 1‐methyl‐3‐phenyl‐5‐p‐methoxyphenylpyrazole, respectively. When methyl‐hydrazine was made to react with 1‐p‐methoxyphenyl‐3‐phenyl‐2‐propyn‐1‐one, a pyrazole was obtained which proved to be identical with 2. Confirmatory evidence for this identity was obtained from their spectral data.
13C, 1H and 31P dynamic NMR studies of tetraalkyldiphosphanes: Barrier to internal rotation about the PP Bond in tetraisopropyldiphosphane
Authors: Albrand J. P. , Cogne A. , Taieb C.
Published: May 2005

The 1H, 31P and 13C NMR spectra of tetramethyldiphosphane (1), tetraethyldiphosphane (2) and tetraisopropyldiphosphane (3) have been studied in the temperature range 30 to −150°C and at magnetic induction up to 5.87 T. In the range −100 to −135 °C, the 1H and 13C spectra of 3 show important changes which can be attributed to freezing the interconversion between two equivalent non‐trans conformations. The line shape analysis of the 13C signals leads to ΔG≠ = 29.4 kJ mol−1 at −113 °C for the dynamic process involved. The spin coupling parameters 1J(PP) and N(PC) = 1J(PC) + 2J(PC) observed for 1 in the temperature range 30 to −120 °C show variations which could be due to a preference for the trans conformation in this diphosphane.
13C NMR study of isoxazolines and isoxazolidines in the thiophene and benzo[b]thiophene S‐oxide and S,S‐dioxide series
Authors: Durand Robert , Geneste Patrick , Olivé Jean‐Louis
Published: May 2005

The 13C NMR spectra were recorded for isoxazolines and isoxazolidines from 2,4,6‐trimethylbenzonitrile oxide or α‐phenyl‐N‐phenyl nitrone as dipolarophiles with the thiophene and benzo[b]thiophene S‐oxide and S,S‐dioxide series. The effects of the isoxazoline or isoxazolidine groups are not very different. Owing to the electronegativity of the oxygen atom, the main influence arises from the regioselectivity of the addition to the carbon atoms located at the α or β position from SO or SO2.
Analysis of 1H NMR spectra of fluorene and azafluorenes: Long‐range coupling constants
Authors: Fomichov A. A. , Lawani‐Edogiawerie S. O. , Prostakov N. S.
Published: May 2005

Analyses of the 1H NMR spectra of fluorene, 2‐nitrofluorene, 1‐azafluorene, 2‐azafluorene, 4‐azafluorene, 7‐nitro‐4‐azafluorene and 1,4‐diazafuorene have been carried out using computer calculations and homo double resonance techniques. The relative signs and magnitude of the 4J, 5J and 6J long‐range coupling constants of the 9‐CH2 group protons with the pyridine and phenylene ring protons have been measured by five‐ and six‐spin calculations. It was established that the presence of substituents and the N heteroatom has only a very weak effect on the values and signs of these coupling constants. The usual alternating signs of long‐range coupling constants involving π‐electron systems were confirmed, giving negative signs for even and positive signs for odd numbers of bonds separating the coupling protons.
Carbon‐13 NMR spectra of 1,4‐benzodiazepines—influence of the 7‐substituent
Authors: Paul H.‐H. , Sapper H. , Lohmann W. , Kalinowski H. O.
Published: May 2005

Carbon‐13 NMR spectra of 1,4‐benzodiazepines, substituted differently at C‐7, are reported. With increasing electron demand of the substituent the signal of C‐2 is shifted upfield, an effect which is interpreted in terms of a π‐polarization of the carbonyl π‐electrons. This mechanism also seems to be of importance for the π‐electrons of the 5‐phenyl substituent and of the (N‐4)(C‐5) bond. Owing to the formation of hydrogen‐bonded self‐associates, compounds with a free amide group show concentration‐dependent shifts of some resonances. This is most obvious for C‐2, the proposed proton accepting site for hydrogen‐bonded cyclic dimers.