Carbon-13 Satellites Research Articles

Determination of chemical purity and isotopic composition of natural and carbon-13-labeled arsenobetaine bromide standards by quantitative(1)H-NMR.

In this study, we report the characterization of three arsenobetaine-certified reference materials by quantitative NMR. We have synthesized an arsenobetaine bromide high-purity standard of natural isotopic composition (ABET-1) and two carbon-13-labeled isotopic standards (BBET-1 and CBET-1). Assignments of the chemical purity and isotopic composition are not trivial in the case of arsenobetaine, and in this study we utilized quantitative(1)H-NMR techniques for the determination of the mass fractions (chemical purity). The isotopic purity of all three standards was also assessed by NMR from the carbon-13 satellite signals. The standards are non-hygroscopic, high-purity (ca. 0.99 g/g), and the carbon-13 enrichment for both isotopic standards is x((13)C)≈0.99. These standards are designed for use as primary calibrators for mass spectrometric determination of arsenobetaine in environmental samples.

RαStructures of partially oriented pentafluorobenzenes C6F5X (X = H, Cl, I) as determined from19F NMR spectra with13C satellites

The (19)F spectra with natural-abundance carbon-13 satellites of C(6)F(5)X (X = H, Cl or I) in ZLI 1695 liquid crystal were analysed. Excluding fluorine-fluorine dipolar coupling constants from the fitting, the vibrationally corrected structures of these molecules were derived and compared with those calculated at DFT/B3LYP level of theory with the aug-cc-pVTZ basis set. The results show that pentafluorobenzene did not exhibit noticeable distortion of the aromatic ring, while chloropentafluorobenzene and iodopentafluorobenzene molecules showed some deformations in their determined structures. Relative anisotropies of F-F couplings have been deduced with accuracy for C(6)F(5)H molecule. Due to uncertainties in structure determination of C(6)F(5)Cl and C(6)F(5)I molecules, it was not possible to obtain precise values for all the corresponding anisotropies. In addition, it was found that the orientation of these molecules in the solvent used can be qualitatively explained in terms of dispersion forces.

Improved Analysis of Minor Species in Mixtures Using Carbon-13 Decoupling in One-Dimensional Proton NMR

Proton nuclear magnetic resonance (NMR) is a useful tool to identify and to quantitate species in mixtures of organic chemicals. However, carbon-13 satellites often interfere with the identification and integration of resonances from species at low concentrations (<2%) in such mixtures. Carbon-13 satellites arise from proton coupling to carbon-13 (spin 1/2, 1.1% isotope abundance). Each satellite is 0.55% of the area of the proton resonance for protons bound to carbon-12. The interferences become particularly troublesome when the principal component of the mixture has many or overlapping resonances.

Algorithm based on a new proof of HSVD equations derived without invoking singular-value decomposition

The spectral characteristics of all signals contained in a FID are obtained on the basis of pure matrix calculations. The algorithm bears some resemblance to HSVD ( H. Barkhuijsen, R. de Beer, and D. van Ormondt, J. Magn. Reson. 73, 553, (1987 ), although it does not rely on singular-value decomposition, but rather on the specific properties of XX †, where X is the signal matrix. The eficiency of themethod is demonstrated by the complete analysis of the proton NMR spectrum of ethanol, including carbon-13 satellites.

Improvement of carbon-13 satellite spectra by double difference spectroscopy

Improvement of carbon-13 satellite spectra by double difference spectroscopy

1Hand 19F NMR study with carbon-13 satellites of para-difluorobezene in various nematic liquid crystals: structure and J-coupling anisotropy

The proton and fluorine NMR spectra, with natural-abundance carbon-13 satellites, of para-difluorobenzene dissolved in various nematic liquid crystals are analysed. The complete r α-structure was determined in five liquid crystals solvents and found to be practically independent of the solvent. Evidence has been found of an anisotropy in the indirect fluorine—fluorine and in the three- and four-bond fluorine—carbon couplings whereas the anisotropy of the other fluorine—carbon couplings appears negligible. The isotope effects on fluorine chemical shielding due to the replacement of carbon-12 by carbon-13 are also reported. The substituent effects of fluorine in difluorobenzenes are summarized.

Deuteron quadrupole coupling constants of methyl bromide- d3 and bromoform- d determined by 2H NMR in mixtures of nematic liquid crystals

The deuteron quadrupole coupling constants (DQCC) of methyl bromide- d 3 and bromoform- d were studied as a function of the liquid-crystal solvent by using 2H NMR spectroscopy and observing natural-abundance carbon-13 satellites. Furthermore, the solvent dependence of the DCD bond angle in methyl bromide is reported. The variations of these parameters are discussed in terms of the correlation between molecular vibration and reorientational motion. The DQCCs for methyl bromide- d 3 and bromoform- d are predicted to be 177 ± 1 kHz and 184 ± 1 kHz, respectively.

1H and 19F NMR study of meta-difluorobenzene: Structure, J-coupling anisotropy, and orientational behavior

The proton and fluorine magnetic resonance spectra with natural abundance carbon-13 satellites of meta-difluorobenzene dissolved in nematic liquid crystals were analyzed. The complete r α structure was determined. The structure deviates clearly from hexagonal. Evidence has been found of an anisotropy in the indirect fluorine-fluorine and fluorine-carbon-13 couplings. From the analyses of the 19F and 19F 13C satellite spectra the 13C( 12C) isotope effects on the 19F chemical shift were calculated. The orientational behavior of meta-difluorobenzene was compared with that predicted by theoretical models based on dispersion and repulsion interactions. The data obtained from ZLI 1167 and ZLI 1132 liquid crystals are in agreement with the theory based on dispersion forces, but in other solvents specific interactions also seem to be of importance.

Evaluation of a new broadband decoupling sequence: WALTZ-16

A new scheme for low-power broadband heteronuclear decoupling is described, based on the use of a composite radiofrequency pulse sequence 90°(+ X) 180°(− X) 270°(+ X), incorporated into a repeated cycle or supercycle. Its principal attribute is that the residual splittings on the observed resonances (usually carbon-13) are very small (less than 0.1 Hz) for a wide range of decoupler offsets (approximately − B 2 < ΔB < + B 2). Existing theories of broadband decoupling are used to calculate the effects of various possible instrumental imperfections on decoupling performance. It is concluded that spatial inhomogeneity of the B 2 field has a perceptible influence near the extremes of the decoupler bandwidth. Only 180° shifts of the radiofrequency phase are used, and the performance is remarkably insensitive to the exact setting of this phase shift. Any decoupler which employs a systematic modulation scheme runs the risk of introducing “cycling sidebands” into the observed spectrum; it is demonstrated that with the proposed sequence these sidebands are very weak, particularly when the decoupling cycle and the signal acquisition processes are not synchronized. As an illustration, the broadband-decoupled carbon-13 spectrum of an aniline derivative is recorded showing natural-abundance carbon-13 satellite signals but no appreciable cycling sidebands. The circuit for a practical implementation of this decoupling sequence is described.

Solvent dependence of deuteron quadrupole coupling constants and of methyl angles of some CD 3X compounds determined by NMR of partially oriented molecules

The deuteron quadrupole coupling constants, Q D, and methyl angles of the solute molecules CD 3CN, CD 3Br, CD 3I, and CD 3NO 2 were determined in various liquid-crystal solvents by use of NMR spectroscopy of oriented molecules. Carbon-13 satellites at natural abundance in the 2H or 1H spectra were used for the measurement of the degree of order of the CD bonds. The results reveal a strong solvent dependence of Q D (maximum variation of 26% in CD 3NO 2) as well as of the DCD angle (maximum variation of 2.3 degrees in CD 3I). These large apparent effects are attributed to much smaller real variations occurring in a two-site interaction. A general correlation between increasing anisotropy of the solvent diamagnetic susceptibility, decreasing Q D, and increasing DCD angle is observed.

Etude du fluorure de propargyle par RMN en phase nematique: Determination de la geometrie moleculaire et des signes des differentes constantes de couplage indirect

NMR spectra of proton, fluorine-19 and carbon-13 satellites of partially oriented propargyl fluoride have enabled the complete structure of this molecule to be determined. Agreement with microwave results is excellent, except for the carbon-fluorine bond length. Signs of all indirect coupling constants have been determined.

The structure and orientational behavior of ortho-difluorobenzene in nematic liquid crystals

The 1H and 19F spectra with natural-abundance carbon-13 satellites of ortho-difluorobenzene dissolved in the nematic ZLI 1167 and ZLI 1132 liquid crystals were recorded and analyzed. The r α structure of ortho-difluorobenzene was determined in both solutions. The analyses of the 19F spectra and 19F 13C satellite spectra yielded the 13C( 12C) isotope effects on the 19F chemical shifts and provided evidence of the indirect contributions to some 19C 19F dipole-dipole coupling constants. The nature of the orienting forces was studied by calculating theoretical relationships between the two independent ordering matrix elements of ortho-difluorobenzene by simple models based on dispersion and repulsion forces. For the thermotropic ZLI 1132 and ZLI 1167 liquid crystals, the results are well fitted by a curve based on the dispersion forces, but for other liquid crystals specific interactions also seem to affect the orientation.

Therα-structure and orientational behaviour of monoiodobenzene in nematic liquid crystals

The 1H N.M.R. spectrum with carbon-13 satellites of monoiodobenzene dissolved in a nematic liquid crystal was recorded and analysed. The r α-structure was obtained by using the force field of monobromobenzene in the calculation of the harmonic vibrational corrections to the dipole-dipole coupling constants. The H-C and C-C bond lengths and the CCC and CCH bond angles are reported. The nature of the orienting forces was studied by calculating the theoretical relationships between the two independent ordering matrix elements for monoidobenzene using simple models based on dispersion and repulsion forces. The results strongly suggest that dispersion forces are decisive in thermotropic ZLI 1132 and ZLI 1167 liquid crystals and significant also in some lyotropic liquid crystals.

ChemInform Abstract: THE Rα STRUCTURE OF 1,6,6AΛ4‐TRITHIAPENTALENE AND 1,6‐DIOXA‐6AΛ4‐THIAPENTALENE. A PROTON NMR STUDY IN THE NEMATIC PHASE INCLUDING CARBON‐13 SATELLITES IN NATURAL ABUNDANCE

Chemischer InformationsdienstVolume 12, Issue 50 Physical Organic Chemistry ChemInform Abstract: THE Rα STRUCTURE OF 1,6,6AΛ4-TRITHIAPENTALENE AND 1,6-DIOXA-6AΛ4-THIAPENTALENE. A PROTON NMR STUDY IN THE NEMATIC PHASE INCLUDING CARBON-13 SATELLITES IN NATURAL ABUNDANCE T. BJORHOLM, T. BJORHOLMSearch for more papers by this authorJ. P. JACOBSEN, J. P. JACOBSENSearch for more papers by this authorC. TH. PEDERSEN, C. TH. PEDERSENSearch for more papers by this author T. BJORHOLM, T. BJORHOLMSearch for more papers by this authorJ. P. JACOBSEN, J. P. JACOBSENSearch for more papers by this authorC. TH. PEDERSEN, C. TH. PEDERSENSearch for more papers by this author First published: December 15, 1981 https://doi.org/10.1002/chin.198150063AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume12, Issue50December 15, 1981 RelatedInformation

The rα structure of monobromobenzene partially oriented in a nematic liquid crystal solvent. The use of 13C satellites in the 1H NMR spectrum

The proton magnetic resonance spectrum with carbon-13 satellites of monobromobenzene in a nematic liquid crystal solvent was recorded and analyzed. The HH and CH dipolar coupling constants corrected for harmonic vibrations were used to determine the r α structures of the proton and carbon skeletons. The proton-proton, proton-carbon, and carbon-carbon internuclear distance ratios as well as the bond angles are reported. The proton structure was found to be hexagonal within the experimental errors, while the carbon structure turned out to be clearly deformed. The effect on the molecular structure of small deviations in force fields was tested using the force field of bromobenzene on the one hand and the modified force field of chlorobenzene on the other to calculate the harmonic corrections for the dipolar coupling constants. The resulting structures are identical within the error limits.

The structure of ethylene oxide determined by liquid-crystal NMR, including carbon-13 satellites

The NMR spectrum of ethylene oxide has been analyzed for carbon-13 satellites in the liquid crystal, Merck ZLI 1167. Structures derived from vibrationally corrected direct couplings indicate good agreement with gas-phase results. Application of vibrational corrections to previous couplings gives structural parameters suggesting significant distortions from above studies.

N.M.R. study of monofluorobenzene partially oriented in thermotropic liquid crystals

The 1H and 19F N.M.R. spectra, with natural abundance carbon-13 satellites, of monofluorobenzene dissolved in the nematic ZLI 1167 and ZLI 1132 liquid crystals were recorded and analysed. The r α-structure of monofluorobenzene was determined in both solutions. The proton structure was also determined in the nematic Phase IV liquid crystal; it was found to be independent of the liquid crystal solvent. However, significant deformations in the carbon skeleton are observable. The indirect contributions to the 13C-19F dipole-dipole coupling constants were found to be negligible. The analysis of the 19F spectra and 19F-13C satellite spectra yielded the 13C(12C) isotope effects on the 19F chemical shifts. These shifts are comparable with those observed in normal solvents or in the isotropic phase of liquid crystal solutions.

ChemInform Abstract: THE Rα STRUCTURE OF ISOXAZOLE, PARTIALLY ORIENTED IN LIQUID‐CRYSTAL SOLVENTS, FROM PROTON SPECTRA AND CARBON‐13 SATELLITES: SOLVENT‐INDUCED STRUCTURE DEFORMATIONS

Chemischer InformationsdienstVolume 12, Issue 31 Physical Organic Chemistry ChemInform Abstract: THE Rα STRUCTURE OF ISOXAZOLE, PARTIALLY ORIENTED IN LIQUID-CRYSTAL SOLVENTS, FROM PROTON SPECTRA AND CARBON-13 SATELLITES: SOLVENT-INDUCED STRUCTURE DEFORMATIONS R. AMBROSETTI, R. AMBROSETTISearch for more papers by this authorD. CATALANO, D. CATALANOSearch for more papers by this authorC. A. VERACINI, C. A. VERACINISearch for more papers by this authorG. CHIDICHIMO, G. CHIDICHIMOSearch for more papers by this authorM. LONGERI, M. LONGERISearch for more papers by this author R. AMBROSETTI, R. AMBROSETTISearch for more papers by this authorD. CATALANO, D. CATALANOSearch for more papers by this authorC. A. VERACINI, C. A. VERACINISearch for more papers by this authorG. CHIDICHIMO, G. CHIDICHIMOSearch for more papers by this authorM. LONGERI, M. LONGERISearch for more papers by this author First published: August 4, 1981 https://doi.org/10.1002/chin.198131050Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume12, Issue31August 4, 1981 RelatedInformation

ChemInform Abstract: DETERMINATION OF THE Rα‐STRUCTURE OF PARTIALLY ORIENTED MONOCHLOROBENZENE UTILIZING THE CARBON‐13 SATELLITES IN THE PROTON NMR SPECTRUM

Chemischer InformationsdienstVolume 10, Issue 31 Physical Organic Chemistry ChemInform Abstract: DETERMINATION OF THE Rα-STRUCTURE OF PARTIALLY ORIENTED MONOCHLOROBENZENE UTILIZING THE CARBON-13 SATELLITES IN THE PROTON NMR SPECTRUM P. DIEHL, P. DIEHLSearch for more papers by this authorJ. JOKISAARI, J. JOKISAARISearch for more papers by this author P. DIEHL, P. DIEHLSearch for more papers by this authorJ. JOKISAARI, J. JOKISAARISearch for more papers by this author First published: July 31, 1979 https://doi.org/10.1002/chin.197931059AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume10, Issue31July 31, 1979 RelatedInformation

EPR spectra of sulfur-33-labeled dimethoxybenzonorbornyl thiyl free radicals

Thiyl (1-aziridyl thiyl) radicals were prepared from benzonorbornadiene and dimethoxybenzonorbornadiene: the linewidths of the EPR spectrum of the latter were sufficiently narrow for carbon-13 satellites to be resolved. Two carbon hyperfine splitting constants were measured having values of 0.315 ± 0.002 and 0.145 ± 0.003 mT: a small splitting of 0.0318 ± 0.0003 mT from the 7- anti hydrogen was also discerned. The radical from dimethoxybenzonorbornadiene was enriched with 48.62% sulfur-33 when it was established that the radical contains only one sulfur atom; the hyperfine splitting constant of -0.277 ± 0.003 mT is consistent with the fact that the sulfur is directly bonded to nitrogen. Digital recording and data processing were used as an aid to accurate line position measurement and to spectrum analysis.