Magnetic Resonance in Chemistry

Cover image for Vol. 53 Issue 9

Early View (Online Version of Record published before inclusion in an issue)

Edited By: Dr James Keeler

Impact Factor: 1.179

ISI Journal Citation Reports © Ranking: 2014: 30/44 (Spectroscopy); 94/157 (Chemistry Multidisciplinary); 107/139 (Chemistry Physical)

Online ISSN: 1097-458X

VIEW

  1. 1 - 66
  1. Letter - correspondence

  2. Research articles

    1. Through-space 19F–19F spin–spin coupling in ortho-fluoro Z-azobenzene

      Shiva K. Rastogi, Robert A. Rogers, Justin Shi, Christopher T. Brown, Cindy Salinas, Katherine M. Martin, Jacob Armitage, Christopher Dorsey, Gao Chun, Peter Rinaldi and William J. Brittain

      Article first published online: 1 SEP 2015 | DOI: 10.1002/mrc.4327

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      19F–19F through-space coupling has been observed in ortho-fluoro Z-azobenzene and is supported by 2D COSY and J-resolved NMR. The distance between interacting fluorines was determined X-ray and theory and does not agree with current empirical formulas for the dependence of through-space coupling on the distance between interacting fluorines.

    2. A detailed mechanistic investigation into the reaction of 3-methylpentanoic acid with Meldrum's acid utilizing online NMR spectroscopy

      Anna L. Dunn, Anna Codina, David A. Foley, Brian L. Marquez and Mark T. Zell

      Article first published online: 31 AUG 2015 | DOI: 10.1002/mrc.4317

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      A thorough investigation into the mechanism of the reaction of 3-methylpentanoic acid and Meldrum's acid using online NMR spectroscopy is reported. Structural characterization of a number of reaction species is presented, providing evidence of the productive intermediates to product formation.

    3. Accurate grading of brain gliomas by soft independent modeling of class analogy based on non-negative matrix factorization of proton magnetic resonance spectra

      K. Ghasemi, M. Khanmohammadi and H. Saligheh Rad

      Article first published online: 31 AUG 2015 | DOI: 10.1002/mrc.4326

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      1H-MRS is a non-invasive technique in assessment of brain's metabolites. The performance of Soft Modeling Class Analogy (SIMCA) classifier was improved by application of non-negative matrix factorization for accurate grading of brain glioma.

  3. Special issue research articles

    1. Improving the performance of J-modulated ADEQUATE experiments through homonuclear decoupling and non-uniform sampling

      Josep Saurí, Teodor Parella, R. Thomas Williamson and Gary E. Martin

      Article first published online: 31 AUG 2015 | DOI: 10.1002/mrc.4322

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      Enhancement of J-modulated ADEQUATE experiments through homodecoupling (HD) and non-uniform sampling (NUS) are described. Sensitivity (s/n) is enhanced by homodecoupling and resolution in the F1 frequency domain is enhanced by the application of NUS. Improvements in the experiments can be exploited to save time or conversely to achieve higher s/n in the same time. The modifications facilitated the measurement of nJCC couplings of < 3 Hz with the J-modulated 1,n-HD-ADEQUATE sequence.

  4. Reviews

    1. Fast acquisition of multidimensional NMR spectra of solids and mesophases using alternative sampling methods

      Philippe Lesot, Krzysztof Kazimierczuk, Julien Trébosc, Jean-Paul Amoureux and Olivier Lafon

      Article first published online: 31 AUG 2015 | DOI: 10.1002/mrc.4290

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      Multidimensional nuclear magnetic resonance experiments provide unique information on the atom-level structure and dynamics of solids and aligned molecules, but their acquisition can be prohibitively long. We review here the different methods that have been employed to accelerate these experiments.

  5. Special issue research articles

    1. A method based on covariance and pattern recognition for improving resolutions of spatially encoded NMR spectra

      Wenqi Qiu, Youhe Chen, Zhiliang Wei, Jian Yang, Yulan Lin and Zhong Chen

      Article first published online: 31 AUG 2015 | DOI: 10.1002/mrc.4305

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      In this contribution, the single-scan spatially encoded technique is integrated with the covariance method for yielding correlated spectra with decent spectral resolutions in direct and indirect dimensions. A reference-less self-correction operation based on pattern recognition is introduced to eliminate artifacts.

  6. Research articles

    1. Effect of thermal treatment on potato starch evidenced by EPR, XRD and molecular weight distribution

      Ewa Bidzińska, Marek Michalec and Dominika Pawcenis

      Article first published online: 31 AUG 2015 | DOI: 10.1002/mrc.4310

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      Effect of heating of the potato starch was studied by quantitative EPR, X-ray diffraction and molecular weight measurements. For the heating parameters not exceeding 230 °C and 30 min a linear relationship was found between the number of thermally generated radicals, determined by EPR, and changes in the starch structure, whereas above these threshold values, a significant increase in the radical amount occurred and rapid reduction in crystallinity. Threshold values, established by EPR should not be exceeded in order to avoid excessive damages of the starch structure.

  7. Letter - spectral assignments

    1. Structure elucidation of configurational isomers of nitrile-substituted spirocyclopropyloxindoles by NMR spectroscopy, molecular modeling, and X-ray crystallography

      J. Benjamín García-Vázquez, Daphne E. González-Juárez, Martha S. Morales-Ríos, Oscar R. Suárez-Castillo and Yolanda Mora-Pérez

      Article first published online: 25 AUG 2015 | DOI: 10.1002/mrc.4293

    2. New phenolic compounds from the lichen Parmotrema praesorediosum (Nyl.) Hale (Parmeliaceae)

      Bui Linh Chi Huynh, Duy Hoang Le, Yukiko Takenaka, Takao Tanahashi and Kim Phi Phung Nguyen

      Article first published online: 25 AUG 2015 | DOI: 10.1002/mrc.4316

    3. Structure and conformations of 2-substituted and 3-substituted alumolanes in polar solvents: a direct NMR observation

      T. V. Tyumkina, D. N. Islamov, L. V. Parfenova, L. M. Khalilov and U. M. Dzhemilev

      Article first published online: 25 AUG 2015 | DOI: 10.1002/mrc.4311

  8. Special issue editorial

  9. Special issue research articles

    1. Fast experiments for structure elucidation of small molecules: Hadamard NMR with multiple receivers

      Peter Gierth, Anna Codina, Frank Schumann, Helena Kovacs and Ēriks Kupče

      Article first published online: 25 AUG 2015 | DOI: 10.1002/mrc.4292

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      We propose several significant improvements to the PANSY (Parallel NMR SpectroscopY) experiments—PANSY COSY and PANSY-TOCSY. In cases where experiments are sampling limited rather than sensitivity limited dramatic reduction of experiment time is achieved by using Hadamard encoding. The proposed PANSY experiments provide sufficient information to allow the CMCse software package (Bruker) to solve structures of small organic molecules.

  10. Research articles

    1. Theoretical study of a simple rotational-echo double-resonance NMR for homonuclear spin-1/2 pairs

      Daisuke Kuwahara, Takahiro Sakuragi and Chikai Tei

      Article first published online: 25 AUG 2015 | DOI: 10.1002/mrc.4325

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      This simple rotational-echo double-resonance (REDOR) technique can produce a reduction in rotational echo amplitude for a homonuclear spin pair undergoing magic angle spinning. The homonuclear REDOR technique has an intriguing condition under which the homonuclear spin pair can be regarded as a heteronuclear spin pair in calculating the reduction in rotational echo amplitude.

    2. Refinement of the inversion-transfer NMR experiment for faster characterization of chemical exchange

      Evelyne Baguet

      Article first published online: 25 AUG 2015 | DOI: 10.1002/mrc.4320

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      It is shown theoretically that the inversion-transfer experiment used to estimate the value of unidirectional rate constants in chemical exchange systems can be performed faster via a reduction of the recovery delay. The chemical exchange rate constants can then be estimated accurately with a formula close to that of standard inversion transfer and easy to use, after a justified approximation. The validity of this theoretical result was checked experimentally with a solution of N,N-dimethylacetamide in which chemical exchange arises from internal hindered rotation.

  11. Special issue research articles

    1. Reconstruction of full high-resolution HSQC using signal split in aliased spectra

      Mohammadali Foroozandeh and Damien Jeannerat

      Article first published online: 20 AUG 2015 | DOI: 10.1002/mrc.4283

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      The ambiguities of the chemical shifts in aliased spectra can be deciphered using pulse sequences encoding the missing information into multiplet structure. The reconstructed full-width high-resolution 1H-13C HSQC spectra provide 15-to 25-fold better resolution than conventional spectra.

    2. Exploiting the phase of NMR signals to carry useful information. Application to the measurement of chemical shifts in aliased 2D spectra

      Karla Ramírez-Gualito and Damien Jeannerat

      Article first published online: 20 AUG 2015 | DOI: 10.1002/mrc.4301

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      The phase of the signals obtained using a modified 2D pulse sequence can carry low-precision but useful information. It is sufficient to resolve the ambiguities in chemical shift caused by spectral aliasing. This approach, we called PHANA, produces spectra where signals with mixed phases can be decoded at the processing to reconstruct full spectra with a 15-fold increase in resolution.

  12. Special issue mini-reviews

    1. Non-uniform sampling: post-Fourier era of NMR data collection and processing

      Krzysztof Kazimierczuk and Vladislav Orekhov

      Article first published online: 20 AUG 2015 | DOI: 10.1002/mrc.4284

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      Non-uniform sampling and novel signal processing techniques offer notable improvement in spectra resolution and sensitivity. But how do they work? Why do we need so many methods to replace old good Fourier transform? Which of the methods to use and is there the best one?

  13. Research articles

    1. Saturated amine oxides: part 10. hydroacridines: part 32. linear 17O/13C and 13C/13C chemical shift correlations between saturated azaheterocyclic N-methylamine N-oxides, and the methiodides of their parent amines

      Francisc Potmischil

      Article first published online: 20 AUG 2015 | DOI: 10.1002/mrc.4286

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      A good linear 17O/13C correlation (r = 0.9778) was found between the chemical shifts of the N+―O group oxygens in monocyclic, bicyclic, and tricyclic N-methylpiperidine-derived saturated amine N-oxides, and those of the N+―CH3 methyl groups analogously situated in the methiodides of their parent amines. In addition, an equally good 13C/13C shift correlation (r = 0.9785) is found between the N+―CH3 methyl groups in the N-oxides and those analogously situated in the appropriate methiodides. Both of these correlations can be used for unambiguous assignment of the configurations of N+―O and N+―CH3 groups in saturated azaheterocyclic amine N-oxides.

  14. Letter - spectral assignments

    1. 1H and 13C NMR assignments of sesquiterpenes from Dysidea fragilis

      Nguyen Xuan Nhiem, Nguyen Thi Cuc, Dan Thi Thuy Hang, Do Thi Trang, Nguyen Hoai Nam, Pham Hai Yen, Do Cong Thung, Vu Kim Thu, Hoang Le Tuan Anh, Bui Huu Tai, Chau Van Minh and Phan Van Kiem

      Article first published online: 20 AUG 2015 | DOI: 10.1002/mrc.4288

  15. Research articles

    1. Theoretical and experimental 15N NMR study of enamine–imine tautomerism of 4-trifluoromethyl[b]benzo-1,4-diazepine system

      Valentin A. Semenov, Dmitry O. Samultsev, Alexander Yu. Rulev and Leonid B. Krivdin

      Article first published online: 20 AUG 2015 | DOI: 10.1002/mrc.4296

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      The tautomeric structure of 4-trifluoromethyl[b]benzo-1,4-diazepine system in solution has been evaluated by means of the calculation of 15N NMR chemical shifts of individual tautomers in comparison with the averaged experimental shifts to show that the enamine–imine equilibrium is entirely shifted toward the imine form.

    2. Application of high-field NMR spectroscopy for characterization and quantitation of submilligram quantities of isolated natural products

      Aleksej Krunić and Jimmy Orjala

      Article first published online: 20 AUG 2015 | DOI: 10.1002/mrc.4304

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      Comparisons of SNR achieved with a combination of different NMR sample tubes and across various NMR platforms. Maximum enhancements at ultrahigh field were applied to structure characterization and quantitation of natural products.

  16. Letter - application notes

    1. Fast determination of the 1H relaxivities of MRI contrast agents

      Abhishek Gupta, Scott A. Willis, Timothy Stait-Gardner, Minoo J. Moghaddam and William S. Price

      Article first published online: 20 AUG 2015 | DOI: 10.1002/mrc.4314

  17. Research articles

    1. NMR spectral properties of the tetramantanes – nanometer-sized diamondoids

      Alexandru T. Balaban, Donald C. Young, Janez Plavec, Klemen Pečnik, Matevž Pompe, Jeremy E. Dahl and Robert M. K. Carlson

      Article first published online: 19 AUG 2015 | DOI: 10.1002/mrc.4289

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      1H and 13C NMR spectral data for the three tetramantane isomers are reported and used to develop general strategies for assignments of higher diamondoids/nanodiamonds. Key features include the use of isobutyl methine loci, 4JHH, W-coupled spin networks, Schlegel diagrams, and recognition of improper hydrogen bonding effects, employed through the use of COSY and HMBC methods. NMR data for the lower diamondoids are reviewed and also applied in development of the assignment strategies.

    2. Magnetic field dependence of spatial frequency encoding NMR as probed on an oligosaccharide

      D. Pitoux, Z. Hu, B. Plainchont, D. Merlet, J. Farjon, D. Bonnaffé and N. Giraud

      Article first published online: 12 AUG 2015 | DOI: 10.1002/mrc.4281

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      The magnetic field dependence of spatial frequency encoding NMR techniques is addressed through an analysis of proton correlation spectra acquired on a saccharide molecule.It is shown that the performance of pure shift and J-edited techniques implemented using this approach is systematically better at higher field. The significant resolution enhancements observed on the resulting spectra acquired at high field make them valuable tools for the assignment of chemical shifts and scalar couplings in molecules with crowded spectrum such as carbohydrates.

  18. Mini-reviews

  19. Letter - spectral assignments

  20. Special issue research articles

    1. Broadband excitation pulses with variable RF amplitude-dependent flip angle (RADFA)

      Martin R. M. Koos, Hannes Feyrer and Burkhard Luy

      Article first published online: 11 AUG 2015 | DOI: 10.1002/mrc.4297

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      Using the optimal control theory-derived GRAPE algorithm, broadband pulses with scalable effective flip angle have been studied in detail. Adjustable pulses promise applicability in fast pulsing experiments, for example, utilizing Ernst angle excitation. Next to optimization and characterization, experimental verification is shown.

  21. Letter - spectral assignments

    1. Structure elucidation of a new isoflavone by exclusive use of 1H NMR measurements

      Alfredo R. Ortega, Rubén A. Toscano, Angelina Hernández-Barragán, Celina Alvarez-Cisneros and Pedro Joseph-Nathan

      Article first published online: 10 AUG 2015 | DOI: 10.1002/mrc.4278

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      The leaves of Piscidia carthagenensis provided new 7,2',5'-trimethoxy-3',4'-methylenedioxyisoflavone (1), admixed with known 6,7-dimethoxy-3',4'-methylenedioxyisoflavone (2), and 5,4'-dihydroxy-7,2',5'-trimethoxyisoflavone (3), which were separated by extensive fractional solubillization. Selective irradiation of the H-5 “singlet” of 2 allowed distinction of the two methoxy group signals, whose chemical shift difference is only 0.004 ppm (1.2 Hz at 300 MHz). The 1H and 13C NMR data of 3 were assigned with the aid of HETCOR and gHMBC measurements. Although 1 looked inhomogeneous in the solid state, its solution structure followed from 1H NMR measurements, where it looked homogeneous. To clarify the solid state aspect and confirm the structure of 1, two types of crystals were mechanically separated and subjected to single crystal X-ray diffraction measurements. This study revealed polymorphism because of the concomitant presence of orthorhombic and triclinic crystals, but showed no atropisomerism. The structure of 3 was also verified by X-ray diffraction crystallography.

    2. 1H and 13C NMR spectral assignments of 2-pyrone derivatives from an endophytic fungus of sarcosomataceae

      Jie-Feng Tian, Ru-Jian Yu, Xiao-Xia Li, Hao Gao, Liang-Dong Guo, Jin-Shan Tang and Xin-Sheng Yao

      Article first published online: 10 AUG 2015 | DOI: 10.1002/mrc.4282

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    3. Structure elucidation and NMR assignments of two new flavanones from the roots of Artocarpus heterophyllus

      Gang Ren, Jiabing Peng, Aihong Liu, Jian Liang, Wenjun Yuan, Hongling Wang and Junwei He

      Article first published online: 10 AUG 2015 | DOI: 10.1002/mrc.4285

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  22. Research articles

    1. Determination of pKa values of some novel benzimidazole salts by using a new approach with 1H NMR spectroscopy

      Akın Mumcu and Hasan Küçükbay

      Article first published online: 10 AUG 2015 | DOI: 10.1002/mrc.4294

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      A new 1H NMR method to determine the pKa values of benzimidazole salts was developed.

    2. 1H NMR spectra of alcohols in hydrogen bonding solvents: DFT/GIAO calculations of chemical shifts

      John S. Lomas

      Article first published online: 10 AUG 2015 | DOI: 10.1002/mrc.4312

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      1H NMR spectral shifts for OH and CH protons of alkanols in pyridine and DMSO are estimated by density functional theory/gauge-including atomic orbital (DFT/GIAO) calculations on alkanol/solvent complexes. Good corrections between computed and experimental data are found, particularly for DMSO.

  23. Rapid communications

    1. SirX: a selective inversion recovery experiment on X-nuclei for the determination of the exchange rate of slow chemical exchanges between two sites

      Xiulan Xie and Friedrich Bönisch

      Article first published online: 10 AUG 2015 | DOI: 10.1002/mrc.4303

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      Tailored boundary condition, a selective inversion on one signal, simplifies the solutions to the McConnell equations for the time course of magnetization. Both the initial buildup rate and the whole curve contain information of chemical exchange and longitudinal relaxation. As compared with two-dimensional exchange spectroscopy, SirX requires only 10–30% experiment time.

  24. Special issue rapid communication

    1. A new approach to compressed sensing for NMR

      Alan S. Stern and Jeffrey C. Hoch

      Article first published online: 10 AUG 2015 | DOI: 10.1002/mrc.4287

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      A new approach to spectrum analysis of non-uniformly sampled NMR data that regularizes the spectrum using the l1 norm of the real part of the spectrum subject to a constraint that the spectrum is consistent with the measured data to a specified degree is described. This approach is better at suppressing sampling artifacts than using the complex l1 norm, and it enables meaningful comparisons with other spectral estimates (e.g., maximum entropy) by ensuring that the agreement with the measured data is the same.

  25. Special issue research articles

    1. NMR studies of dilithiostyrenes: aggregation, NMR parameters, and DFT calculations for (E)-1-Lithio-2-(o-lithiophenyl)-1-trimethylsilylethen

      Bernd Böhler, Harald Günther, Kerstin Reider, Adalbert Maercker, Dennis Gerbig and Heike Hausmann

      Article first published online: 6 AUG 2015 | DOI: 10.1002/mrc.4298

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      The NMR properties, the structure, and the dynamic behavior of a trimethylsilyl-substituted dilithiostyrene have been determined in solution.

  26. Special issue reviews

    1. Multidimensional NMR spectroscopy in a single scan

      Maayan Gal and Lucio Frydman

      Article first published online: 6 AUG 2015 | DOI: 10.1002/mrc.4271

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      Ultrafast (UF) NMR spectroscopy enables the acquisition of arbitrary multi-dimensional NMR spectra within a single-scan, by applying a series of spatiotemporal manipulations on the spins. This review focuses on the principles of UF NMR and on a few of the advances that has characterized this mode of data acquisition during recent years.

  27. Research articles

    1. Conformational studies of dammarane-type triterpenoids using computational and NMR spectroscopic methods

      Byong-kyu Shin, Jihyung Lee and Tae Hoon Choi

      Article first published online: 6 AUG 2015 | DOI: 10.1002/mrc.4302

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      Stable conformers of two triterpenoids are found by SCC-DFTB-based MD. The NMR chemical shifts of the stable conformers are estimated by QM calculations. The calculated chemical shifts show good agreement with the experimental values.

  28. Special issue research articles

    1. Reaction monitoring using online vs tube NMR spectroscopy: seriously different results

      David A. Foley, Anna L. Dunn and Mark T. Zell

      Article first published online: 6 AUG 2015 | DOI: 10.1002/mrc.4259

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      A kinetic rate analysis of three reaction processes reveals that rates derived from nuclear magnetic resonance (NMR) analysis are highly dependent on monitoring method. These findings indicate that users must be aware of the effect of their monitoring method upon the kinetic rate data derived from NMR analysis.

  29. Research articles

    1. A new NMR approach for structure determination of thermally unstable biflavanones and application to phytochemicals from Garcinia buchananii

      Timo D. Stark, Sofie Lösch, Mathias Salger, Onesmo B. Balemba, Junichiro Wakamatsu, Oliver Frank and Thomas Hofmann

      Article first published online: 20 JUL 2015 | DOI: 10.1002/mrc.4269

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      1,1-ADEQUATE could be used successfully as a powerful alternative approach to confirm the C-C connectivities in manniflavarone without producing sample heating ‘stress’ and loss in resolution in signal multiplicity. Two new structures could be isolated, (2R,3S,2″R,3″R)-GB-27″-O-β-d-glucopyranoside and (2R,3S,2″R,3″R)-manniflavanone-7″-O-β-d-glucopyranoside, and were elucidated by spectroscopic analysis including 1D NMR and 2D NMR and mass spectrometry methods. The absolute configurations of these highly anti-oxidative compounds were determined by a combination of NMR and ECD spectroscopy.

    2. Dynamic NMR study of dinitrophenyl derivatives of seven-membered cyclic ketals of pyridoxine

      Ilfat Z. Rakhmatullin, Leisan F. Galiullina, Marsel' R. Garipov, Alexey D. Strel'nik, Yurii G. Shtyrlin and Vladimir V. Klochkov

      Article first published online: 20 JUL 2015 | DOI: 10.1002/mrc.4251

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      Conformational features and dynamic processes for dinitrophenyloxy derivatives of seven-membered cyclic ketals of pyridoxine were studied by dynamic NMR experiments. These compounds are involved in two conformational exchange processes. One process is the rotation of the dinitrophenyl fragment around the C—O bond, and the second process is a conformational transformation of the seven-membered cycle. Activation barriers of both conformational exchange processes were determined using line shape analysis of the NMR spectra with variation of temperature.

  30. Special issue research articles

    1. Complete 1H NMR assignment of cedranolides

      Nury Perez-Hernandez, Barbara Gordillo-Roman, Daniel Arrieta-Baez, Carlos M. Cerda-Garcia-Rojas and Pedro Joseph-Nathan

      Article first published online: 1 JUL 2015 | DOI: 10.1002/mrc.4246

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      The complete 1H NMR assignment of ten members of the cedranolide family, including economically important α-cedrene and cedrol, is described using the iterative full spin analysis included in the PERCH NMR software (PERCH Solutions Ltd., Kuopio, Finland). The coupling constants were correlated with the conformational preferences of the cedranolides calculated using the complete basis set method.

  31. Letter - spectral assignments

    1. NMR structural assignments for four new 6-methoxy-tetrahydro-ß-carboline derivatives

      Teik Beng Goh, Mohd Nizam Mordi, Mas Rosemal Hakim Mas Haris and Sharif Mahsufi Mansor

      Article first published online: 1 JUL 2015 | DOI: 10.1002/mrc.4273

  32. Research articles

    1. Standardless multicomponent qNMR analysis of compounds with overlapped resonances based on the combination of ICA and PULCON

      Yulia B. Monakhova, Dirk W. Lachenmeier, Thomas Kuballa and Svetlana P. Mushtakova

      Article first published online: 1 JUL 2015 | DOI: 10.1002/mrc.4275

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      A NMR method for simultaneous quantification has been established based on the combination of chemometric ICA treatment for spectra decomposition and the PULCON principle for absolute quantification. The proposed method was applied for analysis of model mixtures and fruit juices with recoveries between 90% and 111%. The proposed method is a unique tool for rapid simultaneous quantification of up to six components in case of spectral overlap and the absence of reference materials.

  33. Special issue research articles

    1. CLIP–ASAP-HSQC for fast and accurate extraction of one-bond couplings from isotropic and partially aligned molecules

      Johanna Becker and Burkhard Luy

      Article first published online: 1 JUL 2015 | DOI: 10.1002/mrc.4276

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      The combination of rapid ASAP-HSQC and clean inphase doublets of the CLIP-HSQC allows the acquisition of 2D experiments for coupling determination in 25 s or faster. The approach is demonstrated on several test samples measuring 1JCH coupling constants and 1DCH residual dipolar couplings (RDCs).

  34. Research articles

    1. Three-dimensional structure of cyclic antibiotic teicoplanin aglycone using NMR distance and dihedral angle restraints in a DMSO solvation model

      Nina C. Gonnella, Nelu Grinberg, Mark Mcloughlin, Om Choudhary, Keith Fandrick and Shengli Ma

      Article first published online: 1 JUL 2015 | DOI: 10.1002/mrc.4279

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      The solution conformation of teicoplanin aglycone was determined using NOE and dihedral angle restraints in a DMSO solvation model. Backbone 13C chemical shifts showed good agreement with those computed at the density functional level of theory. The results showed that a hydrogen-bonded DMSO molecule in combination with NMR-derived restraints enabled calculation of structures that satisfied experimental data.

  35. Errata

    1. Constant time gradient HSQC-iDOSY: practical aspects

      A. S. McLachlan, J. J. Richards, A. R. Bilia and G. A. Morris

      Article first published online: 30 JUN 2015 | DOI: 10.1002/mrc.4277

  36. Letter - spectral assignments

  37. Special issue research articles

    1. Investigation of the reaction of 1,3-dimethylurea with formaldehyde by quantitative on-line NMR spectroscopy: a model for the urea–formaldehyde system

      Oliver Steinhof, Günter Scherr and Hans Hasse

      Article first published online: 12 JUN 2015 | DOI: 10.1002/mrc.4274

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      Quantitative on-line NMR spectroscopy is applied to study the equilibria and the reaction kinetics of the reaction of formaldehyde with 1,3-dimethylurea. This reaction system is employed as a model system for the much more complex but industrially relevant urea–formaldehyde system. Detailed peak assignment data for 1H, 13C, and 15N and reaction kinetic and equilibrium data at industrially relevant reaction conditions including all model parameters and a detailed description of the model are provided.

  38. Research articles

    1. Resolution-enhanced 2D NMR of complex mixtures by non-uniform sampling

      Adrien Le Guennec, Jean-Nicolas Dumez, Patrick Giraudeau and Stefano Caldarelli

      Article first published online: 6 JUN 2015 | DOI: 10.1002/mrc.4258

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      Resolution-enhanced non-uniform sampling is evaluated in the context of complex mixture analysis for HSQC and TOCSY pulse sequences. With this approach, resolution in the indirect dimension can be increased without sensitivity or time penalties in HSQC, decreasing the chances of peak overlapping. Multiplet splitting can also be seen in the indirect dimension for TOCSY, improving the chances of metabolite identification.

  39. Editorials

    1. MRC review of 2014

      ▪ ▪

      Article first published online: 27 MAY 2015 | DOI: 10.1002/mrc.4245

  40. Special issue mini-reviews

    1. Monitoring organic reactions by UF-NMR spectroscopy

      Antonio Herrera, Encarnación Fernández-Valle, Roberto Martínez-Álvarez, Dolores Molero-Vílchez, Zulay D. Pardo-Botero and Elena Sáez-Barajas

      Article first published online: 21 MAY 2015 | DOI: 10.1002/mrc.4240

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      Ultrafast NMR has undoubtedly opened up new perspectives in monitoring dynamic systems as they happen in real time. It has permitted to study in-depth fast organic reactions and transient species participating in their mechanisms. In the present review are shown some results that highlight the potential of the methodology.

  41. Special issue research article

    1. Relaxation NMR as a tool to study the dispersion and formulation behavior of nanostructured carbon materials

      David Fairhurst, Terence Cosgrove and Stuart W. Prescott

      Article first published online: 18 MAY 2015 | DOI: 10.1002/mrc.4218

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      Solvent relaxation NMR gives a measure of the surface areas and wettability of various nanostructured carbons including nano carbon blacks, graphene oxides, nanographites and porous graphenes. A range of solvents including water, ethanol and tetrahydrofuran can be used. Relaxation measurements are shown to give good results on opaque, concentrated dispersions directly from production. Differences in total surface area due to different milling processes can be observed as well as the negative impact of using excess dispersant.

  42. Special issue review

    1. Hyphenated low-field NMR techniques: combining NMR with NIR, GPC/SEC and rheometry

      Volker Räntzsch, Manfred Wilhelm and Gisela Guthausen

      Article first published online: 9 APR 2015 | DOI: 10.1002/mrc.4219

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      Hyphenated low-field NMR techniques are promising characterization methods for online process analytics and comprehensive offline studies of soft materials. In this review, we present a combination of near-infrared spectroscopy and time-domain NMR (TD-NMR) relaxometry, online 1H-NMR spectroscopy after size exclusion chromatographic (SEC, also known as GPC) separation and a combination of rheometry and TD-NMR relaxometry for highly viscous materials. Case studies are reviewed that underline the possibilities and challenges of the different methods.

  43. Special issue mini-reviews

    1. New applications and perspectives of fast field cycling NMR relaxometry

      Rebecca M. Steele, Jean-Pierre Korb, Gianni Ferrante and Salvatore Bubici

      Article first published online: 9 APR 2015 | DOI: 10.1002/mrc.4220

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      We will focus on the most recent developments in fast field cycling NMR relaxometry instrumentation and applications and future perspectives of how this technology will be applied in both academic and industrial contexts to study the molecular dynamics in a wide range of substances and materials or simply for fingerprinting or quality control purposes.

  44. Special issue research articles

    1. Automated data evaluation and modelling of simultaneous 19F–1H medium-resolution NMR spectra for online reaction monitoring

      Nicolai Zientek, Clément Laurain, Klas Meyer, Andrea Paul, Dirk Engel, Gisela Guthausen, Matthias Kraume and Michael Maiwald

      Article first published online: 9 APR 2015 | DOI: 10.1002/mrc.4216

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      The Calibration samples were analysed under stationary conditions. The flow rates in the monitoring experiments were slow enough to ensure entirely magnetised nuclei. Flow effects only influences the peak width which was compensated by the corresponding evaluation method.

    2. Simple 17O NMR method for studying electron self-exchange reaction between UO22+ and U4+ aqua ions in acidic solution

      István Bányai, Ildikó Farkas and Imre Tóth

      Article first published online: 8 APR 2015 | DOI: 10.1002/mrc.4235

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      We found that 17O enriched UO22+ ions loose the enrichment by adding U4+ into their acidic aqueous solution. The process could be followed by means of quantitative 17O NMR spectroscopy. The detailed kinetic analysis of the 17O isotope exchange resulted in the experimental determination of electron self-exchange between UO22+ and UO2+ ions, in good agreement with earlier estimates and recent quantum chemical calculations. A new acid independent reaction path was identified as well.

  45. Special issue mini-reviews

    1. Fast hybrid multi-dimensional NMR methods based on ultrafast 2D NMR

      Serge Akoka and Patrick Giraudeau

      Article first published online: 31 MAR 2015 | DOI: 10.1002/mrc.4237

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      Hybrid multi-dimensional methods based on ultrafast 2D NMR lead to improved sensitivity and resolution in a short time. Such strategies open the way to numerous practical application of spatially-encoded methods. This mini-review aims at describing the principles, the recent advances, and the latest applications of these hybrid techniques.

  46. Special issue research articles

    1. Application of 19 F time-domain NMR to measure content in fluorine-containing drug products

      Maria Victoria Silva Elipe, Lan Li, Karthik Nagapudi, Alan M. Kook, Carlos Cobas, Isaac Iglesias and Chen Peng

      Article first published online: 13 MAR 2015 | DOI: 10.1002/mrc.4223

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      The average drug content of three fluorinated drug products, cinacalcet, lansoprazole, and ciprofloxacin, were measured using low field 19 F TD-NMR to compare with the reported label claims (doses ranging from 15 to 500 mg). The data suggest that the technique is suitable for quality control and development work to measure the average amount of drug substance in formulated drugs containing fluorine. TD-NMR is a simple, non-destructive technique and excellent PAT tool for development and manufacturing in the pharmaceutical industry.

    2. Differentiation of enantiomers by 2D NMR spectroscopy at 1 T using residual dipolar couplings

      Martin R. M. Koos, Ernesto Danieli, Federico Casanova, Bernhard Blümich and Burkhard Luy

      Article first published online: 13 MAR 2015 | DOI: 10.1002/mrc.4222

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      Differentiating enantiomers using 2D bench-top NMR spectroscopy. Spectrometers working with permanent magnets at 1 T field strength allow the acquisition of 2D data sets. In conjunction with previously reported chiral alignment media, this setup allows the measurement of enantiomeric excess via residual dipolar couplings in stretched gelatine as a result of the reduced line width obtained by 2D J-resolved spectroscopy.

    3. Monitoring chemical reactions by low-field benchtop NMR at 45 MHz: pros and cons

      Maria Victoria Silva Elipe and Robert R. Milburn

      Article first published online: 23 JAN 2015 | DOI: 10.1002/mrc.4189

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      Chemical reactions were followed by low-field NMR. A 45 MHz benchtop NMR instrument was tested to monitor three types of reactions by 1D 1H NMR: a Fischer esterification, a Suzuki cross-coupling, and the formation of an oxime. Only protonated solvents were used with no observation of lineshape degradation by magnetic drift. Aliquots were injected over time into the NMR flow cell at the temperature of the magnet. A low signal-to-noise ratio of 10 : 1 for the solvent/analyte signals is reasonable.

  47. Special issue rapid communications

    1. Natural abundant 17O NMR in a 1.5-T Halbach magnet

      Morten K. Sørensen, Oleg N. Bakharev, Ole Jensen and Niels Chr. Nielsen

      Article first published online: 16 JAN 2015 | DOI: 10.1002/mrc.4207

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      We present mobile, low-field 17O NMR as a means for monitoring oxygen in liquids. Whereas oxygen is one of the most important elements, oxygen NMR is limited by a poor sensitivity related to low natural abundance and gyro-magnetic ratio of the NMR active 17O isotope. Here, we demonstrate 17O NMR detection at a Larmor frequency of 8.74 MHz in a 1.5-T Halbach neodymium magnet with a home-built digital NMR instrument suitable for large-scale production and in-line monitoring applications.

  48. Special issue mini-reviews

    1. Spatially resolved chemical reaction monitoring using magnetic resonance imaging

      Kirk W. Feindel

      Article first published online: 14 JAN 2015 | DOI: 10.1002/mrc.4179

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      This mini-review provides an update on the recent use of magnetic resonance imaging (MRI) for spatially resolved chemical reaction monitoring. Examples demonstrating the use of 1H, 7Li, 11B, 19F, and 27Al MRI are included.

    2. NMR spectroscopy to follow reaction progress in ionic liquids

      Bradley J. Butler, Donald S. Thomas, James M. Hook and Jason B. Harper

      Article first published online: 7 OCT 2014 | DOI: 10.1002/mrc.4161

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      This review highlights the advantages of NMR spectroscopy over other analytical techniques in following reaction progress in ionic liquids, particularly addressing the practical aspects of the methodology and highlighting the range of processes that can be readily followed.

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