bluuebunny/crossref_metadata_2025 huggingface dataset:
17O NMR study of chlorinated anisoles
Authors: Kolehmainen E. , Knuutinen J.
Published: May 2005

The 17O NMR chemical shifts of anisole and all 19 chlorinated anisoles measured in CDCI3 at ambient temperature show a dispersion of approximately 40 ppm. The substituent chemical shifts (SCS) of di‐ or more highly chlorinated compounds cannot be reproduced by addition of single substituent effects. Theoretical calculations of the 17O NMR chemical shifts have been attempted by molecular mechanical and semi‐empirical molecular orbital methods at the INDO level, but the results are not satisfactory.
Improved 13C1H shift correlation spectra for indirectly bonded carbons and hydrogens: The FLOCK sequence
Authors: Reynolds William F. , McLean Stewart , Perpick‐Dumont Marion , Enríquez Raül G.
Published: May 2005

Several modifications of the basic 13C1H shift correlation sequence as optimized for polarization transfer via long‐range 13C1H coupling constants are described and evaluated. Modifications involve incorporation of BIRD pulse(s) at the mid‐point of the evolution period and/or at the mid‐point of the fixed delay prior to polarization transfer, in addition to the previously discussed incorporation of a BIRD pulse during the final fixed delay. These modifications give significantly improved sensitivity for many cross‐peaks, excellent suppression of one‐bond peaks and, in the case of the sequence incorporating two additional BIRD pulses, some ability to distinguish two‐bond and three‐bond connectivity peaks. The latter sequence is, overall, comparable in sensitivity to the fixed time sequences XCORFE and COLOC. It is also easier to parameterize and gives better suppression of one‐bond peaks and other artifacts.
NMR spectra and stereochemistry of 1,5‐ and 1,6‐disubstituted perhydrooxazolo[3,4‐a] pyridines
Authors: Crabb Trevor A. , Trethewey Andrew N.
Published: May 2005

13C and 1H NMR spectroscopy showed that with the exception of r‐1,t‐6,t‐8a‐1‐alkyl‐6‐ethylperhydrooxazolo[3,4‐a] pyridines (alkyl = ethyl, isopropyl) which adopt the O‐inside cis‐fused conformation, all the other 1 ‐alkyl‐6‐ethyl‐ and 1‐alkyl‐cis(H‐5, H ‐ 8a) ‐5‐ methyl ‐ perhydrooxazolo [3,4‐a] pyridines adopt trans‐fused conformations (CDCI3, 298 K).
Complexes of aluminium with aminopolycarboxylic acids: 27Al NMR and potentiometric studies
Authors: Iyer R. K. , Karweer S. B. , Jain V. K.
Published: May 2005

The reactions of Al3+ ion with a series of aminopolycarboxylic acids containing coordinating sites (denticity, n) ranging from 3 to 8 were studied by potentiometric and 27AI NMR methods. Hydrolysis constants of the complexes were determined by potentiometry. The 27Al {1H} NMR data indicate a nearly linear relationship between the 27Al chemical shift of the normal complex and denticity of the ligand up to n = 6. Hydroxo complexes form in all systems, and at high pH (ca. 10) aluminate forms. Protonated complexes were formed in some cases. Diprotonated complexes of EDTA and PDTA have been identified by 27Al NMR spectroscopy. Maximum deshielding of the 27Al resonance was observed for the octahedral [Al(EDTA)]− complex. The Al‐NTA complex appears to be the most symmetric of the complexes.
13C NMR spectroscopy of aristolochic acids and aristololactams
Authors: Priestap Horacio A.
Published: May 2005

The 13C NMR spectra of more than 30 phenanthrene derivatives were recorded and their carbon shifts assigned. The compounds consisted of representative aristolochic acids and aristololactams, the phenanthrene alkaloid argen‐tinine and some derivatives. Assignments of the carbon resonances were carried out from chemical shifts, one‐bond and long‐range carbon‐hydrogen couplings and selective comparison of the phenanthrene derivatives with each other and with model compounds. The chemical shifts of the aromatic carbons were correlated with substituent effects. It was found that the shift changes on introduction of oxy functions in phenanthrenes parallel those reported for monosubstituted naphthalenes. Steric compression shifts observed in 3,4‐disubstituted and ring A polysubstituted phenanthrenes are discussed. Further evidence about the structures of the aristololactams CII, CIII, DII, DIII, enterocarpam‐I and enterocarpam‐II is provided, based on 13C NMR data. The substituent parameters found for phenanthrene derivatives proved to be additive and their use in signal assignments is described.
Molecular conformation trapping as an aid to chemical shift assignments for multi‐conformation systems: A platinum(II) complex
Authors: Luck Linda A. , Elesser Wendy L. , Hubbard John L. , Bushweller C. Hackett
Published: May 2005

Recent work in our laboratory has shown that 31P{1H} dynamic NMR (DNMR) spectroscopy is useful in studying restricted rotation about the metal‐phosphorus bonds in bulky bis‐phosphine‐di‐halo complexes of platinum(II). Decoalescence is observed and the 31P{1H} NMR chemical shift is clearly sensitive to changes in molecular conformation. However, in most instances, the spectrum of a given conformation is a simple singlet which inherently contains no information regarding molecular geometry. Assignment of a given singlet to a specific conformation is problematic. A method is described for obtaining unequivocal assignment of NMR signals to specific molecular conformations by using DNMR spectroscopy. x‐ray crystallography and dissolution of the conformationally homogeneous crystals at very low temperatures (‘molecular conformation trapping’). This methodology should be useful for the analysis of any multi‐conformation system which has a sufficiently high energy barrier to conformational equilibration.
13C NMR of coumarins. II—Khellactones: Spectroscopic criteria to establish the relative configuration of the dihydropyran ring
Authors: Macías F. A. , Massanet G. M. , Rodríguez‐Luis F. , Salvá J. , Fronczek F. R.
Published: May 2005

The 13C NMR data of several khellactone derivatives are reported. 1H NMR‐based stereochemical criteria are evaluated, and a new criterion based on 13C NMR is proposed to establish the relative configuration at C‐3′ and C‐4′ using ΔδC‐3′ between trans and cis isomers and Δδgem(Me)2 values. The structure of trans‐4′‐methylkhellactone was determined by x‐ray analysis.
Two‐dimensional NMR studies of arsenical‐sulfhydryl adducts
Authors: O'Connor Richard J. , McGown Evelyn L. , Dill Kilian , Hallowell Susan F.
Published: May 2005

British anti‐lewisite (2,3‐dimercaptopropanol) (BAL) has long been used as an arsenic antidote, but its therapeutic efficacy is limited by its inherent toxicity. Two less toxic potential replacements for BAL are dimercaptosuccinic acid and dimercaptopropanesulfonic acid. These two disulfhydryl compounds were compared with BAL by studying the structures of their adducts with two organic arsenicals, phenyldichloroarsine and trans‐2‐chlorovinylarsine oxide. The 1:1 adducts were synthesized and characterized by one‐ and two‐dimensional NMR spectroscopy. 1H and 13C spectral data and resonance assignments, verified by spin simulation, are presented for the adducts. All were five‐membered heteroatomic ring systems, with different solubility properties. When stereoisomers were detectable, the ratio of anti to syn isomers varied, indicating that the functional group of the antidote influenced stereochemical aspects of adduct formation.
2‐(4′‐Substituted) phenylisatogens: Analysis of 13C substituent chemical shifts
Authors: Stoddart B. , Hooper M.
Published: May 2005

The 13C NMR spectra for eight 2‐(4′‐substituted)phenylisatogens were determined at 30°C in CDCl3. Analysis of the ipso‐carbon SCS values was carried out using the well known DSP and DSP‐NLR models. Changes in the 13C SCS values for the carbon atoms in the isatogen moiety suggest that a small degree of inter‐ring mesomeric resonance is possible between the ring systems. A three‐parameter model, which give better overall agreement than either the DSP or DSP‐NLR models, is proposed for the ipso‐carbon SCS. The question of whether or not the isatogen moiety exhibits amphielectronic behaviour is still unresolved.
Carbon‐13 chemical shielding tensors in alkanedicarboxylic acids. Influence of molecular geometry on the carboxyl carbon tensors in alkanedicarboxylic acids and related compounds
Authors: Jagannathan N. R.
Published: May 2005

The principal elements of 13C chemical shift tensors in some dicarboxylic acids were determined from powder samples by two methods: (i) from the theoretical fit of the experimental data and (ii) from the side‐band intensities of the CP‐MAS spectra using the graphical procedure of Herzfeld and Berger. Neither the methylene nor the carboxyl carbons are axially symmetrical. The methylene tensors corresponding to higher dicarboxylic acids were not analysed owing to severe overlap of the different carbon tensors. The influence of local molecular geometry on the carbon 13C chemical shielding tensors in dicarboxylic acids and other related organic molecules are also reported. The σ22 component of the tensor shows a linear correlation as a function of the structural parameter, the OCO bond angle, around this carboxyl carbon atom. The significance of the symmetry factor calculated for the carboxyl carbons is also presented.
Probing the mechanism of ligand exchange by two‐dimensional NMR spectroscopy
Authors: Hampden‐Smith Mark J. , Ruegger Heinz
Published: May 2005

The application of two‐dimensional chemical exchange NMR spectroscopy to the elucidation of ligand‐exchange mechanisms in inorganic complexes is addressed. Specific examples involving inter‐ and intra‐molecular phosphine exchange in platinum and mercury complexes are given, and the generality of the technique is discussed.
Steric and electronic effects on 195Pt NMR chemical shifts of platinum (II) phosphine complexes
Authors: Clark Howard C. , de P. Nicholas A. Martin
Published: May 2005

Platinum‐195 chemical shift measurements for cis‐PtCl2(PCy3)2 and trans‐PtXCl(PCy3)2 (X = H, Cl, SnCl2Ph and SnCl3) in methylene chloride solution are reported. A comparison of these shifts with those from analogous complexes containing less bulky phosphine ligands indicates significant steric effects on the 195Pt shift of the PCy3 complexes. For cis‐PtCl2(PCy3)2 a downfleld shift of over 200 ppm is obtained. For the cis‐PtCl2(PCy3)2 complexes the deshielding of 195Pt is found to increase in the order X = H < Cl < SnCl3, SnCl2Ph, which corresponds to the change in the bulk of X. The observed downfield shifts in the bulky 2Ph complexes are rationalized in terms of steric crowding, lengthening of the PPt bond and deshielding of the Pt nucleus.
Transfer of substituent influence into the remote aromatic ring in 4′‐R‐dibenzo‐crown ethers
Authors: Loktev V. F. , Mudrakovsky I. L. , Tashmukhamedova A. K. , Stempnevskaya I. A. , Morozova I. J.
Published: May 2005

13C NMR studies of 4′‐R‐dibenzo‐18‐crown‐6 and 4′‐R‐dibenzo‐24‐crown‐8 showed that the substituent influence is transferred through the macrocycle to a remote aromatic ring. The transfer is due to steric effects and depends on crown ether complex formation.
13C and 17O NMR study of methoxy groups in chlorinated Di‐ and trimethoxybenzenes
Authors: Knuutinen J. , Kolehmainen E.
Published: May 2005

13C and 17O NMR data [chemical shifts and 1J(CH) values] for the methoxy groups in isomeric 1,2‐, 1,3‐ and 1,4‐dimethoxybenzenes, 1,2,3‐trimethoxybenzenes and most of their chlorinated derivatives and some related brominated compounds were measured for CDCl3 solutions. The 17O NMR chemical shifts show up to 60 ppm dispersion. Comparison between the compounds with and without adjacent chlorine atoms (2,6‐di‐ and 2,4,6‐tri‐substitution) also showed a clear methoxy carbon chemical shift change. The number and position of the chlorine atoms in the aromatic ring give small but observable effects on the 17O NMR chemical shifts of the methoxy group if it is coplanar with the aromatic plane. Similarly, the degree and nature of the substitution have a minor effect (about 1 Hz) on the 1J(CH) direct coupling values.
13C NMR study of aromatic ring‐substituted (E)‐3‐phenylpropenals and (2E,4E)‐5‐phenylpenta‐2,4‐dienals
Authors: Laihia K. , Pitkänen M. , Nevalainen Tapio
Published: May 2005

13C and 1H chemical shifts together with C,H and H,H coupling constants are presented for (E)‐3‐phenylpropenal, (2E,4E)‐5‐phenylpenta‐2,4‐dienal and their o‐OCH3‐ and o‐, m‐ and p‐NO2‐substituted derivatives. The SCSs calculated for the aldehyde chains show similar effects on the ring carbons, except in the para position where the shorter chain causes a 3.3 ppm deshielding and the longer chain a 1.0 ppm shielding effect. This shift difference is reflected in all the ring‐substituted derivatives of the two series of aldehydes, but not in the one‐bond C,H coupling constants.

The effect of aromatic ring substitution on 2J(C,CHO) seems to be mainly inductive in origin. The importance of the structural unit in the study of C,H coupling constants was observed on comparing the 3J(C,H) values in C(sp2)CCH and CCC(2)H pentadienal fragments. In the first type the vicinal coupling varies from 6.5 to 8.8 Hz and in the second from 2.7 to 3.6 Hz. In the latter fragment an s‐cis conformation changes the mutual position of the coupled nuclei, whereas in the former it remains the same as in the s‐trans conformation.
Exceptionally large 13C–13C coupling constants of compounds containing a CF3 group
Authors: Gombler Willy
Published: May 2005

Coupling constants, 1J(13C,13C), of compounds containing a CF3 group are reported. The values for the coupling of the CF3 carbon with the neighbouring carbon are exceptionally large. In a series of compounds in which the CF3 group is bonded to an sp3, sp2 or sp carbon the 1J(C,C) values show a good linear correlation with the product of the s characters of the two orbitals forming the CC bond. Furthermore, compounds containing a CCl3 group have been measured. A correlation of the 1J(CC) values with the sum of the group electronegativities in compounds of the CX3‐CY3 type is found. The results for compounds containing highly electronegative substituents suggest a contribution to the CC coupling from a relatively large variation of the valence‐shell s‐orbital density at the carbon nucleus, Sc2(0). Additional 13C and 19F NMR data of the compounds are presented.
Multinuclear magnetic resonance study of tautomerism in fluorinated β‐diketones
Authors: Salman S. R. , Farrant R. D. , Lindon J. C.
Published: May 2005

Multinuclear NMR experiments on fluorinated β‐diketones have furnished information on the various tautomers present in solution and their proportions. 2‐Trifluoroacetyl‐1‐indalone in CDCI3 solution exists in the enol form, as a mixture of exocyclic and endocyclic cis‐enols with the exocyclic form favoured, but in DMF‐d7 solution the equilibrium shifts to 40% enol, 60% hydrate with the enol and hydrate being in slow exchange on the NMR time scale. 2‐Trifluoroacetyl‐1‐tetralone in CDCI3 solution exists only as the enol forms, approximately equally populated, but in DMF‐d7, unlike the indalone, no hydrate is formed although there is now 6% of the keto form present in slow exchange. The experimental results were compared with calculated data produced using molecular orbital simulations. These agree with the NMR results and predict that the tetralone enol tautomers are both significantly populated at room temperature but that the indalone exists primarily as the exocyclic enol. The oxygen‐oxygen internuclear distance in the hydrogen bond was estimated from the OH proton chemical shift based on a calibration from solid‐state data from model compounds, and agrees well with the predictions using the molecular mechanics approach.
Conformation of zearalenone in solution: A vicinal coupling constant and molecular mechanics study
Authors: Muñoz Luis , Riguera Ricardo
Published: May 2005

Vicinal coupling constants of stereochemical significance were obtained in four solvents for zearalenone and specifically deuteriated zearalenone. Comparison with values calculated for several conformations using molecular mechanics calculations indicates that zearalenone exists in a single conformation in solution. The solvent dependence observed for the H‐9′ and H‐10′ signals cannot be attributed to a conformational equilibrium.
Carbon‐13 and related NMR chemical shifts in alkylammonium and alkylphosphonium salts
Authors: Evans David J. , Leigh G. Jeffery , Macdonald Colin J.
Published: May 2005

The 13C NMR chemical shifts of the α‐carbon atoms in cations [NR4]+, [NR3CH2Ph]+ and [PR4]+ [R = Me, Et, Prn, Bun or Pen (n‐pentyl)] are found at anomalously high field in comparison with the corresponding shifts in RCl or RNH2. This is ascribed in part to the effect of the positive charge. The effect is detectable but less pronounced with β‐carbon atoms, but is not detectable in subsequent carbon atoms in longer alkyl chains.
Applications of INEPT experiments for 119Sn NMR spectroscopy
Authors: Gouron Véronique , Jousseaume Bernard , Ratier Max , Lartigue Jean‐Claude , Petraud Michel
Published: May 2005

The application of a non‐refocusing INEPT pulse sequence in 119Sn NMR spectroscopy allows the determination of nJ(119Sn, 1H) values by comparison of the observed patterns with calculated spectra. It gives an easy access to nJ(119Sn, 1H) values in butyltin derivatives.
ESR study of the reaction of trithiazyl trichloride with primary aromatic amines
Authors: Domschke G. , Mayer R. , Bleisch S. , Bartl A. , Staško A.
Published: May 2005

Benzenamines (1) react with 1,3,5‐trichloro‐1λ4,3λ4,5λ4‐1,3,5,2,4,6‐trithiatriazine (2) to form the novel radicals 2‐(2λ4‐2,4,‐dithia‐1,3‐diaza‐2‐chloro‐1,3‐butadien‐1‐yl)‐2λ4‐2,1,3‐benzothiadiazol‐1‐yls (4) or 2‐(5‐chlora‐2λ4‐2,4‐dithia‐1,3‐diaza‐1,2‐pentadien‐1‐yl)‐2λ4‐2,1,3‐benzothiadiazol‐1‐yls (4′). ESR hyperfine splitting constants of 20 different radicals of type 4 are presented, and the mechanism of their formation and the suggested structure of 4 are discussed.
17O and 31P NMR of aroylphosphanes, aroylsilanes and aroylphosphonates: Absence of resonance in —COPR2 groups (NMR of terminal oxygen, part 5)
Authors: Dahn Hans , Péchy Peter , Van Toan Vien
Published: May 2005

The 17O NMR spectra for aryl‐substituted P,P‐diphenylbenzoylphosphanes (p‐YC6H4COPPh2, 1), trimethylbenzoylsilanes (p‐YC6H4COSiMe3, 2) and dialkyl benzoylphosphonates (p‐YC6H4COPO(OR)2, 3) were recorded. Compounds 1, 2 and 3 show a similar high substituent sensitivity (p+), indicating a strong electron demand of the carbonyl group; as resonance stabilization is not possible in 2 and 3 it is concluded that electron donation from P to carbonyl is equally negligible in 1. The carbonyl oxygen signals of 1, 3 and, in particular, 2 appear at low field. The 31P NMR shifts of 1 were also measured; they are less sensitive to the ring substituents.
Compounds with bridgehead nitrogen. Part 64—conformational equilibria in the 6‐p‐nitrophenylperhydrodipyrido[1,2‐c: 2′,1′‐e]imidazoles
Authors: Banting Lee , Crabb Trevor A.
Published: May 2005

The effect of 6‐substitution on the conformational equilibria of the perhydrodipyrido[1,2‐c:2′,1′‐e]imidazoles has been investigated. r‐6H,t‐11a,t‐11b‐6‐p‐Nitrophenylperhydrodipyrido[1,2‐c:2′,1′‐e]imidazole was found to exist as a pair of enantiomeric non‐interconverting N‐outside‐cis‐syn‐trans conformers, whereas the r‐6H,c‐11a,c‐11b and r‐6H,c‐11a,t‐11b isomers adopted the trans‐syn‐trans conformations. Both syn isomers exhibit restricted rotation of the 6‐p‐nitrophenyl substituent at room temperature and below.
Compounds with bridgehead nitrogen. 65—NMR spectra and stereochemistry of perhydrodiquino[1,2‐c: 2′,1′‐e]imidazoles
Authors: Banting Lee , Crabb Trevor A.
Published: May 2005

The configurations and preferred conformations of six diastereoisomeric perhydrodiquino[1,2‐c:2′,1′‐e]imidazoles have been assigned by 1H and 13C NMR spectroscopy.
Cross‐polarization for quadrupolar nuclei—proton to molybdenum‐95
Authors: Edwards John C. , Ellis Paul D.
Published: May 2005

High‐field, 95Mo, solid‐state nuclear magnetic resonance spectra of (NH4)6Mo7O24 · 4H2O and (Bu4N)2Mo2O7 were obtained using solid‐echo techniques together with 1H cross‐polarization and dipolar decoupling. The results show that reliable second‐order powder line shapes can be obtained with excellent cross‐polarization enhancements of 66–86% of maximum theoretical enhancement. The lower than maximum enhancements are due to the relatively long TIS values, which are similar in magnitude to the TH1ρ values. Experiments were performed which reveal the dynamics involved in the cross‐polarization process, including measurement of the cross‐relaxation time constant and the 1H and 95Mo rotating‐frame spin‐lattice relaxation times. It was found that the principal relaxation process causing low gain in the observed signal was the 1H T1ρ, which was found to be on the order of 23–24 ms. The experimental results obtained indicate that selective cross‐polarization dynamics occur in molybdenum cluster species with inequivalent molybdenum sites. The 95Mo rotating‐frame spin‐lattice relaxation rate is long in comparison with the other relaxation processes, making molybdenum a good cross‐polarization candidate but precluding the use of multiple contact cross‐polarization.
1H and 13C NMR studies of isomerism in hydroxamic acids
Authors: Brown David A. , Glass William K. , Mageswaran Rajeswary , Mohammed Salima Ali
Published: May 2005

1H and 13C NMR studies of N‐methyl‐substituted hydroxamic acids, RCON(CH3)OH (R = CH3, C2H5 and C6H5), show that the series exhibits cis–trans isomerism about the CN bond. The Z/E ratio increases in the series CH3 < C2H5 < n‐C5H11 < n‐C6H13 for a given solvent, indicating that steric interaction between R and the OH group is more important than that between R and the CH3 group. In DMSO‐d6 the Z isomer is preferentially stabilized by solvation, whereas in C6D6 and toluene‐d8 the unsolvated E form is thermodynamically more stable, as predicted by ab initio molecular orbital calculations. (12) At high concentrations (in CDCl3, CD2Cl2, C6D6 and toluene‐d8) the E isomer may also be stabilized by intermolecular association. In the O‐methyl‐substituted series, RCONHOCH3 (R = CH3, C6H5), although the Z isomer predominates in all solvents, at low temperatures there is evidence for enolic forms.
Study of the distribution of the π‐electrons in push‐pull alkenes by 1H and 13C NMR spectroscopy
Authors: Fischer G. , Rudorf W.‐D. , Kleinpeter E.
Published: May 2005

Push‐pull alkenes with variable structure were investigated with respect to the influence of the different substituents at the central C,C double bond on the dynamic behaviour of this type of compound. 1H and 13C NMR spectroscopic investigations were carried out for ketene‐S,S‐, ‐S,N‐ and ‐N,N‐acetals. HMO calculations were employed to discuss the related π‐electron density distributions.
An explanation of anomalous artifact intensity in fully 1H–1H decoupled two‐dimensional chemical shift correlation spectroscopy
Authors: Bain Alex D. , Burton Ian W. , Carpenter Katharine , Reynolds William F.
Published: May 2005

Two‐dimensional heteronuclear chemical shift correlation experiments which attempt decoupling in f1 have been shown to give artifacts in strongly coupled systems. In particular, COLOC and HETRES experiments on methylene groups show an artifact midway between the two proton lines. This paper provides an explanation of the artifact intensity behaviour with respect to the strength of coupling between the methylene protons. Experimental results on 1,2‐dibromoethylbenzene are presented, and theoretical calculations were carried out on the COLOC experiment and a mathematical model was developed which predicted the artifact appearance and intensity. Simulations were also performed using the simulation program SIMPLTN to verify the experimental and theoretical results.
13C NMR spectra of the models for the end‐group analysis of polybutadiene
Authors: Podkorytov I. S. , Lubnin A. V.
Published: May 2005

The 13C NMR spectra of models for the initial and terminal monomeric unit diads of polybutadiene are interpreted. The models are C10H18, diolefins, separated from the mixture of oligomers which are formed in the reaction of buta‐1,3‐diene with ethyllithium and a proton donor. A version of the INADEQUATE pulse sequence with DEPT polarization transfer and a selective DANTE read pulse is described and used for assignment.
Structure of the De‐O‐acetylated glucuronoxylomannan from Cryptococcus neoformans serotype D, as determined by 2D NMR spectroscopy
Authors: Skelton Marshall A. , Cherniak Robert , Poppe Leszek , van Halbeek Herman
Published: May 2005

The primary structure of the de‐O‐acetylated glucuronoxylomannan isolated from Cryptococcus neoformans serotype D was characterized de novo by NMR spectroscopy. Assignment of the 1H and 13C spectra of the polysaccharide involved a combination of 2D NMR experiments including double‐quantum‐filtered {1H,1H} COSY, {1H,1H} TOCSY and 1H‐detected {1H,13C} heteronuclear multiple quantum coherence spectroscopy. The sequence of the glycosyl residues, including the linkage positions, was deduced by {1H,1H} rotating‐frame NOE (ROESY) spectroscopy. The serotype‐D glucuronoxylomannan was found to be a branched polymer with a repeating pentasaccharide unit of the following structure: magnified image.
Influence of gauche interactions on the substituent effects on carbon‐13 chemical shifts in six‐membered ring compounds
Authors: Rajan K. Pandia , Manimekalai A.
Published: May 2005

13C NMR spectra of six epimeric substituted 4‐hydroxypiperidines and two corresponding piperidines were recorded. Substituent parameters for equatorial methyl, gem‐dimethyl, equatorial hydroxy and axial hydroxy groups were calculated from the 13C chemical shifts of these compounds and several other six‐membered ring compounds. The effects of nearby substituents on these parameters were examined. It is concluded that the magnitude and even the sign of the α effect is modified by the presence of nearby substituents. It was found that gauche interactions play an important role in determining the magnitude of the α effect. However, the β effect is not influenced by the nearby substituents except for the gem‐dimethyl group. The magnitude of the γ effect is almost independent of the nearby substituents.
13C, 6Li and 7Li NMR T1 and T1ρ study of ion‐pair dynamics and structure of lithium fluorenide
Authors: Sethson Ingmar , Eliasson Bertil , Edlund Ulf
Published: May 2005

The rate of interconversion between tight and loose ion pairs of lithium fluorenide in 2‐methyltetrahydrofuran was determined from 7Li relaxation in the rotating frame. The rate constant for the tight to loose ion‐pair interconversion at −60°C is 2.3 × 104 s−1 and for the reverse process 2.6 × 103 s−1. The 13C relaxation times (T1) of the fluorenyl anion, adjusted for viscosity changes, do not change significantly with the ion‐pair structure. The electric quadrupole relaxation contribution to the 7Li T1 was derived from 6Li and 7Li T1 measurements. Lower limits of 7Li quadrupole splitting constants (QSCs) were obtained from the 7Li quadrupolar and the 13C dipole‐dipole relaxation times. The QSC values are in the range 37–200 kHz and appear to reflect changes in the ion‐pair structure, with a low value corresponding to a solvent‐separated ion pair. The higher value for the contact ion pair is in agreement with a structure where the anion disrupts the symmetrical coordination of solvent molecules around the cation. A decreased QSC and a shortened 13C T1 at high temperature for the diethyl ether solution may be caused by aggregation.
Study of fluorinated blowing agents in polyurethane foams by fast magic angle spinning fluorine‐19 NMR spectroscopy
Authors: Jackson Peter , Carr Robert H.
Published: May 2005

Using magic angle spinning 19F NMR, it has been possible to identify gaseous chlorofluorocarbon (CFC) and hydrochlorofluorocarbon (HCFC) blowing agents trapped in the cells of test samples of polyurethane foam. On spinning the samples at rates greater than 10 kHz, further signals have been observed corresponding to rigidly held CFC and HCFC molecules absorbed in the solid polymer. Differences are seen between a sample taken from the centre of a foam block and a sample taken from the block edge, possibly indicating some localized decomposition of the blowing agent(s) within the solid polymer.
59Co and 99Ru NMR investigation of heterometallic carbonyl clusters. Reactivity of [MCo3(CO)12]− (M = Fe, Ru) towards NO+; formation of RuCo3(CO)11(NO) and FeCo2(μ3‐NH)(CO)9
Authors: Braunstein Pierre , Rosé Jacky , Granger Pierre , Richert Thierry
Published: May 2005

A series of mixed‐metal carbonyl clusters containing Co and Ru atoms was investigated by 59Co NMR and, for the first time in cluster chemistry, by 99Ru NMR. These techniques were successfully used to follow the reactivity of these complexes towards nitrosylation by NO+. Whereas [NEt4] [RuCo3(CO)12] reacts with [NO]BF4 with the formation of RuCo3(CO)11(NO), which subsequently fragments into RuCo2(CO)11 and Co(CO)3(NO), [NEt4] [FeCo3(CO)12] leads inter alia to FeCo2(μ3‐NH)(CO)9, in which the coordinated NO ligand has been reduced.
Synthesis, tautomerism and stereochemistry of spiropyrazolines
Authors: Tóth Gábor , Lévai Albert , Duddeck Helmut
Published: May 2005

1,3‐Dipolar cycloaddition of (E)‐ and (Z)‐arylidene‐1‐tetralone derivatives affords trans‐ and cis‐spiro‐1‐pyrazolines, respectively, regio‐ and stereo‐selectively in a one‐step reaction. These rearrange into spiro‐2‐pyrazolines on proton catalysis. The relative configurations and conformations of the spiropyrazolines were elucidated by different NMR methods.
Complete 1H and 13C NMR spectral assignment of patchoulenone, a tricyclic sesquiterpene ketone
Authors: Hisham A. , Wray V. , Pieters L. , Claeys M. , Dommisse R. , Vlietinck A.
Published: May 2005

A tricyclic sesquiterpene ketone, patchoulenone, was isolated from the hexane extract of the root bark of Uvaria narum Wall. (Annonaceae). Its structural elucidation was based on detailed 2D NMR spectroscopy, leading to the complete assignment of the 1H and 13C NMR spectra.
Stereochemical study of anagyrine‐type quinolizidine alkaloids by 15N and 2D NMR spectroscopy
Authors: Liu Zimin , Yang Li , Jia Zhongjian , Chen Jihong
Published: May 2005

The configurations of anagyrine, thermopsine and two other anagyrine‐type quinolizidine alkaloids were revised using 15N and 2D NMR in a 400 MHz NMR study. Their 1H and 13C NMR chemical shifts are given in detail.
Interpretation of the 13C NMR spectra of thirteen methoxycarbonylpyridines and some of their derivatives
Authors: Jokela Reija
Published: May 2005

The 13C NMR spectra of thirteen methoxycarbonylpyridine derivatives and two pyridine lactones are interpreted. The substituent increments for the methoxycarbonyl group in 2‐, 3‐ and 4‐substituted pyridines are reported.
Determination by NMR methods of the structure and stereochemistry of astellatol, a new and unusual sesterterpene
Authors: Sadler Ian H. , Simpson Thomas J.
Published: May 2005

The full structure of astellatol, a new complex sesterterpene isolated from Aspergillus variecolor, was determined solely by the use of one‐ and two‐dimensional NMR techniques. The carbon skeleton was deduced from a two‐dimensional INADEQUATE spectrum, and the proton shifts were deduced from a two‐dimensional CH correlation (HMQC) experiment. Analysis of a two‐dimensional proton DQFCOSY spectrum and a series of homonuclear NOE difference spectra allowed the determination of the full stereochemistry.
Two‐dimensional NMR spectra of hydrolysable tannins which form equilibrium mixtures
Authors: Yoshida Takashi , Hatano Tsutomu , Okuda Takuo
Published: May 2005

The structures of hydrolysable tannins, each existing as an equilibrium mixture due to tautomerization at the sugar core(s) or at the dehydrohexahydroxydiphenoyl group (five‐ and six‐membered hemiacetal forms) in the molecule, were elucidated by NMR, employing 2D NMR techniques (COSY, NOESY, 1H13C long‐range COSY, etc.), on derivatives which avoid the spectral complication due to equilibration.
C‐19 configurational assignments in some morphine derivatives by homonuclear NOE
Authors: Batta Gy. , Gunda T. E. , Szabó Z. , Berényi S. , Gulyás Gy. , Makleit S.
Published: May 2005

Azidolysis‐thermolysis of C‐19 diastereomer tosyl esters of morphine derivatives resulted in the formation of a new substituted 4‐azatetracyclo [4.4.02,4.03,8] decane ring system. As the course of such transformations depends on the chirality of C‐19, its relative configuration was determined both in the starting materials and in the new compounds. To this end a semiquantitative 1H{1H} NOE interpretation was combined with MMX molecular mechanics. Interestingly, both in the starting materials with a rotating C‐7—C‐19 bond and in the fairly rigid aziridine ring‐containing products, the same (H‐8α{19‐Me}) NOE effects were the most informative on the stereochemistry. In addition full a priori 1H and 13C assignments of 13 compounds are presented.
Solution conformation of mono‐ and difucosyllactoses as revealed by rotating‐frame NOE‐based distance mapping and molecular mechanics and molecular dynamics calculations
Authors: Ejchart Andrzej , Dabrowski Janusz , von der Lieth Claus‐Wilhelm
Published: May 2005

The solution conformation of two fucosyllactoses, Fucα(1 → 2)Galβ(1 → 4)Glcα,β and Galβ(1 → 4) [Fucα(1 → 3)] Glcα,β, and a difucosyllactose, Fucα(1 → 2)Galβ(1 → 4)[Fucα(1 → 3)]Glcα,β, were investigated in Me2SO‐d6 with the use of distance mapping, molecular mechanics (MM) energy minimization and molecular dynamics (MD) simulations. The distance mapping procedure, which was based on rotating‐frame NOE constraints involving C‐ and O‐linked protons, and hydrogen bonding constraints, suggested the occurrence of two conformations for each of the fucose residues. The MM calculations resulted in two minima that were located reasonably near to the regions demarcated in the Θ, Ψ conformational space by distance mapping; 500 ps MD trajectories showed transitions between two conformations characterized by glycosidic angles Θ and Ψ that only deviated insignificantly from those found by the first two methods. No similar transitions were observed for the Galβ14Glc linkage.
Ab initio IGLO study of the syn/anti dependence of the 13C NMR chemical shifts in simple amides
Authors: Jiao Ding , Barfield Michael , Hruby Victor J.
Published: May 2005

The syn/anti dependences of the alkyl 13C chemical shifts provide a useful probe of stereochemistry around the amide bonds in peptides and proteins. To investigate these dependences the ab initio IGLO method was used to obtain the 13C chemical shielding for the following series of amide molecules as models for the peptide bond: syn‐ and anti‐N‐methylformamide (NMF), cis‐ and trans‐N‐methylacetamide (NMA), N,N‐dimethylformamide (DMF) and N,N‐dimethylacetamide (DMA). Molecular geometries for shielding calculations are optimized ones at the HF/6–31G* level. Good correlations were observed between the calculated 13C chemical shift results and the experimental data. The syn/anti dependence of 13C chemical shifts around amide bonds is perdicted either with double‐ζ or triple‐ζ quality basis sets. Based on an analysis of the paramagnetic bond contributions (PBC) to the chemical shieldings, it is concluded that the syn/anti dependence of the 13C chemical shifts in amides arises almost entirely from the PBC of the syn and anti NC bonds, and is completely analogous to the electronic origin for the cis/trans γ‐effect in hydrocarbons.
1H, 13C and 15N NMR study of N1‐alkyl‐N2‐arylthioureas
Authors: Wawer Iwona , Koleva Vera
Published: May 2005

13C and 15N NMR chemical shifts were measured for N1‐alkyl‐N2‐arylthioureas. The absence of decoalescence of the N1‐alkyl group carbon signals down to 190 K, the europium‐induced chemical shifts and the molecular mechanics calculations indicate that the preferred conformation is E,Z. Solvent effects suggest that N1‐alkyl‐N2 arylthioureas exist as dimers, forming an eight‐membered ring hydrogen bonded complex. In N1, N1‐dimethyl‐N2‐phenylthiourea the barrier to rotation around the CN1 bond is 47 kJ mol−1 (from 13C NMR, in CD2Cl2). The upfield N1‐CH3 signal in both the 1H and 13C NMR spectra results from the methyl group anti to the CS and the low‐field signal from the syn methyl group.
Multinuclear magnetic resonance study of oxaziridines
Authors: Čudić Mane , Herrmann Rudolf
Published: May 2005

NMR data (13C, 15N, 17O) for the three ring atoms of various oxaziridines are compared. Their significance for the prediction of the enantioselectivity of the oxidation of sulphides by chiral oxaziridines is discussed.
Conformational characteristics of kessane studied by 600 MHz 1H NMR and molecular mechanics
Authors: Lankhorst Peter P. , van Beek Teris A. , Haasnoot Cornelis A. G.
Published: May 2005

The conformational characteristics of kessane were investigated by means of 600 MHz 1H NMR spectroscopy and molecular mechanics (MM2) calculations. Accurate vicinal 1H1H coupling constants were obtained by means of extensive computer simulations. These experimental values were compared with coupling constants calculated by the combined use of MM2 calculations and the generalized Karplus equation. It is shown that kessane adopts a single conformation in solution which is only slightly different from the conformation predicted by the MM2 calculations. The cyclopentane ring of kessane is characterized by a pure 1E conformation. The cycloheptane ring adopts a conformation which is situated precisely between the twist‐chair TC9 and the chair C5 conformation on the pseudo‐rotational pathway of the seven‐membered ring.
1H and 13C NMR data for 2‐O‐, 3‐O‐and 2,3‐di‐O‐glycosylated methyl α‐and β‐D‐galactopyranosides
Authors: Shashkov Alexander S. , Nifant'ev Nikolay E. , Amochaeva Vera Yu. , Kochetkov Nikolay K.
Published: May 2005

1H and 13C NMR data for a series of 2‐O‐, 3‐O‐ and 2,3‐di‐O‐glycosylated methyl α‐and β‐D‐gluco‐ and β‐D‐galactopyrano‐sides are presented. The glycosylation effects on the spectra of disaccharides and the deviations from additivity values in the spectra of trisaccharides were determined.
13C NMR data for several cyclolignans
Authors: Feliciano A. San , Del Corral J. M. Miguel , Gordaliza M. , Castro M. A.
Published: May 2005

13C NMR shielding data for 100 naturally occurring and hemisynthetic cyclolignans are tabulated. Some of them have been compiled from the literature. The data have been assigned on the basis of 2D heteronuclear 1H‐13C correlations.
Water exchange on [Gd(H2O)8]3+ and [Gd(PDTA)(H2O)2]‐ in aqueous solution: A variable‐pressure, ‐temperature and ‐magnetic field 17O NMR study
Authors: Micskei Károly , Powell D. Hugh , Helm Lothar , Brücher Ernö , Merbach André E.
Published: May 2005

17O NMR longitudinal and tranverse relaxation rates and chemical shifts were measured at variable temperature at three magnetic fields (1.4, 4.7 and 9.4 T) for aqueous solutions of the complexes [Gd(H2O)8]3+ and [Gd(PDTA)(H2O)2]−. The transverse relaxation rates and chemical shifts were analysed in the light of recent EPR line width measurements to obtain the parameters for water exchange kinetics: k = (8.30 ± 0.95) × 108 and (1.02 ± 0.10) × 108 s−1, ΔH‡ = 14.9 ± 1.3 and 11.0 ± 1.4 kJ mol−1 and ΔS‡ = −24.1 ± 4.1 and −54.6 ± 4.6 J K−1 mol−1 for [Gd(H2O)8]3+ and [Gd(PDTA)(H2O)2]−, respectively. The longitudinal relaxation rates were used to obtain the parameters for the rotation time of the complexes: τ = (2.9 ± 0.2) × 10−11 and (7.9 ± 0.3) × 10−11 s and Ec = 15.1 ± 1.5 and 19.2 ± 1.1 kJ mol−1 for [Gd(H2O)8]3+ and [Gd(PDTA)(H2O)2]−, respectively. The 17O NMR transverse relaxation rates were measured at variable pressure, and were used to determine the activation volumes for the water exchange process: ΔV0‡ = −3.3 ± 0.2 and −1.5 ± 0.5 cm3 mol−1 for [Gd(H2O)8]3 + and [Gd(PDTA)(H2O)2]−, respectively. It can be concluded that water exchange occurs via an associative limiting A mechanism for [Gd(H2O)8]3 + (without excluding Ia) and an associative interchange, Ia, mechanism for [Gd(PDTA)(H2O)2]−. These water exchange kinetic and mechanistic results are compared with those for the heavy Ln3+ aqua ions and the Gd3+ complexes with DTPA5− and DOTA4−.
1H 3D NOE‐NOE spectrum of met‐cyanomyoglobin: The first 3D NMR spectrum of a paramagnetic protein
Authors: Banci Lucia , Bermel Wolfgang , Luchinat Claudio , Pierattelli Roberta , Tarchi Dario
Published: May 2005

A 3D NOE‐NOE spectrum of the paramagnetic protein met‐cyanomyoglobin has been successfully obtained. The protein shows hyperfine shifted signals. Planes at their frequencies show clean cross peaks with signals of nearby protons. Connectivities can be detected in‐plane at frequencies corresponding to hyperfine broadened signals beneath the diamagnetic envelope, whose connectivities may be difficult to observe otherwise. The limits of observability of cross peaks are discussed by means of spectral simulations.
1H, 2H and 19F NMR spectroscopy of a novel iron(II) tetradentate cysteine‐peptide complex having only one δ isomer. Detection of two isomers in coordination of CysXYCys bidentate peptide ligands to iron(II) ion
Authors: Sun Wei‐yin , Ueyama Norikazu , Nakamura Akira
Published: May 2005

An Fe(II) complex with Z‐Ala‐CysProLeuCysGlyNHC6H4mF (Z = benzoxylcarbonyl) having an invariant bidentate peptide ligand, CysKYCys, in rubredoxins was synthesized. The contact‐shifted 1H, 2H and 19F NMR signals of (Et4N)2[Fe(ZAlacysProLeucysGlyNHC6H4mF)2] (1) in acetonitrile‐d3 or acetonitrile at 30°C indicate the existence of two isomers (δ and λ) in the solution of bidentate complex 1 with different orientations of the bidentate peptide ligand to a tetrahedral Fe(II) ion. A novel tetradentate cysteine‐containing peptide ligand, cis‐1,2‐cyclohexylene(COAlaCysProLeuCysGlyNHC6H4mF)2, is designed by energy minimum calculations and synthesized. Its Fe(II) complex, (Et4N)2[Fe(cis‐1,2‐cyclohexylene(CO‐Ala‐cys‐Pro‐Leu‐cys‐Gly‐NH‐C6H4‐m‐F)2)], showed only set of contact‐shifted 1H, 2H and 19F NMR signals of Cys CβH2 due to the preferable formation of the δ isomer.
Oxygen‐17 NMR studies of N‐nitrosamines
Authors: Cerioni Giovanni , Giumanini Angelo G. , Verardo Giancarlo , Dahn Hans
Published: May 2005

Natural abundance 17O NMR data for seven aliphatic, nine cyclic and thirteen aromatic N‐nitrosamines, recorded at room temperature in acetonitrile, are reported. Differences in chemical shifts among and within the three groups are discussed in terms of electronic and steric effects. The σ+ value for the N‐nitrosamine group was estimated. A comparison between amides and N‐nitrosamines was made.
The 2D QUADSHIFT experiment: Separation of deuterium chemical shifts and quadrupolar couplings by two‐dimensional solid‐state MAS NMR spectroscopy
Authors: Chandrakumar Narayanan , von Fircks Gero , Günther Harald
Published: May 2005

The two‐dimensional QUADSHIFT experiment is introduced, which permits the separation of chemical shifts and quadrupolar couplings in solid‐state magic angle spinning NMR spectra of powder samples. The technique was applied to partially deuteriated norcamphor and camphor under slow magic angle spinning. Double quantum chemical shift resolutions down to 0.2 ppm were achieved, with double quantum linewidths in the range 6–12 Hz. Separation and correlation of deuterium chemical shifts and quadrupolar couplings is demonstrated for individual sites.
Dynamic and substituent effects in the ESR spectra of triplet biradical intermediates in lithiation reactions of 2‐alkylbenzotriazoles: A cautionary note
Authors: Dalal Nar S. , Xu Ruixin , Katritzky Alan R. , Wu Jing , Jesorka Aldo
Published: May 2005

Investigations of intermediates generated in the course of lithiation of four 2‐alkylbenzotriazoles revealed largescale temperature‐dependent changes in their ESR spectra. A cautionary observation was that the ESR spectra obtained under synthesis conditions exhibited lineshapes that were assignable to a monoradical, while additional, lower temperature measurements clearly showed the species to be a biradical. The electron–electron dipolar couplings yield an average distance between the two unpaired electrons in the biradical, Rav, of about 5.3 ± 0.16 Å. These Rav values are consistent with the unpaired electrons being localized on the nitrogen atoms of the two benzotriazole moieties in the biradical fragment. This conclusion is supported by oxygen trapping (nitroxide radical formation) studies. The biradicals are shown to have triplets as the ground state with a single‐triplet separation of about 26±4 kJ mol−1.
Influence of skeletal alteration of lignoids on carbon‐13 NMR chemical shifts
Authors: Agrawal Pawan K. , Pathak Ashish K.
Published: May 2005

The characteristic 13C NMR chemical shift ranges as a guide for the establishment of the parent skeletons of various categories and subcategories of lignoids (lignans, neolignans and oxyneolignans) and for the determination of the substitution pattern of the side‐chain are tabulated.
Carbon NMR assignment for gnaphaliin 7‐methyl ether
Authors: Reinecke Manfred G. , Minter David E. , Jia Qi
Published: May 2005

The 13C NMR spectrum for gnaphaliin 7‐methyl ether is reported and assigned from XCORFE and HETCOR studies which also suggest a revision in the assignments for the other 5‐hydroxy‐3,7,8‐tri‐methoxyflavones flindulatin and ternatin.
Kinetics and reaction mechanisms of diazo compounds and iodonium salts as studied by chemically induced dynamic nuclear polarisation
Authors: Gragerov I. P. , Levit A. F. , Kiprianova L. A. , Buchachenko A. L.
Published: May 2005

CIDNP phenomena in various reactions of diazo compounds and iodonium salts are described. The various reaction pathways leading to the formation of polarised aromatic products are analysed in detail.
Carbon chemical shifts of 1,1‐diphenylethylene and α‐methylstyrene dimer dianions
Authors: Takahashi Kensuke , Yamada Kaoru , Wakata Kazuyoshi , Asami Ryuzo
Published: May 2005

The natural abundance C‐13 NMR spectra of 1,1‐diphenylethylene and α‐methylstyrene dimer dianions have been obtained using the proton noise decoupling technique. The extra negative charge distributions in the carbanions have been discussed and compared with those obtained from the proton chemical shifts. The chemical shifts of the two ortho carbons in a phenyl ring are equivalent to each other for the former carbanion but not for the latter.
The nuclear magnetic resonance of heterocyclic compounds related to anthracene
Authors: Sharpless Norman E. , Bradley Robert B. , Ferretti James A.
Published: May 2005

The NMR spectra of a series of heterocyclic compounds analogous to anthracene have been investigated at 220 and 60 MHz. Correlations have been made with molecular geometry and parameters calculated from semi‐empirical MO theory. For planar molecules, the chemical shift of the proton ortho to the heteroatom is linear with respect to the electron density on the heteroatom, but otherwise chemical shifts are independent of electron density. Planarity of the molecules is also a factor in some of the coupling constants.
Etude par RMN 13C de quelques époxydes exo et endo dans la série du bicyclo[2.2.1]heptane
Authors: Zimmermann D. , Reisse J. , Coste J. , Plénat F. , Christol H.
Published: May 2005

L'étude RMN 13C de composés époxybicyclo[2.2.1]‐heptaniques fait ressortir une forte influence de l'orientation endo ou exo de l'hétérocycle sur le glissement chimique du 13C pontal. La différence entre les variations de glissements chimiques en 13C et 1H montre que l'effet de courant de cycle ne peut seul rendre compte des résultats observés.
Carbon‐13 NMR spectra of arylmethyl carbanions
Authors: Takahashi Kensuke , Kondo Yoshiharu , Asami Ryuzo , Inoue Yoshio
Published: May 2005

Carbon‐13 chemical shifts of three arylmethyl carbanions have been determined by changing solvents and counter ions. The charge distributions in the carbanions are discussed and compared with those obtained from the 1H chemical shifts.
Studies in organometallic rearrangements IV—proton and carbon nuclear magnetic resonance spectra of group IVA substituted indenes and indenyl anions
Authors: Taylor Glenn A. , Rakita P. E.
Published: May 2005

The proton and carbon NMR spectra for a series of substituted indenes [C9H7R, R = H, CH3, Si(CH3)3] are reported. The proton and carbon resonances for the 5‐membered ring exhibit pronounced changes as a function of the substituents.