Nitrogen NMR Research Articles

Solvent effects on nitrogen NMR shieldings in azines

The ranges of solvent effects on the nitrogen shielding are reported for pyridine, 1,2-1,3-, and 1,4-diazine, and 1,3,5-triazine. These ranges are both significant and variable from about 48 ppm for 1,2-diazine to about 1 I ppm for the triazine. The former is the largest solvent-induced range so far observed in nitrogen NMR. Contributions to the nitrogen shielding ranges from hydrogen bonding and solvent polarity effects are estimated. The former effect usually provides a dominant contribution and can be associated with the strength of the hydrogen bond formed from the solvent to the solute. The contribution to the change in nitrogen shielding from a change in solvent polarity is also significant but usually less than that due to hydrogen bonding. Both effects operate to produce changes in the nitrogen shielding in the same direction. The polarity effects are unusually large in the case of 1,2-diazine and this is corroborated by INDO/S-SOS shielding calculations using the solvaton model.

Study of solvent effects on the nitrogen NMR shieldings of some indolizines

AbstractSolvent effects on the nitrogen NMR shieldings of indolizine and three azaindolizines are presented for a range of thirteen solvents. The results are discussed in terms of hydrogen‐bonding an solvent polarity effects. ‘Pyridine‐type’ nitrogen atoms show a much larger range of solvent effects than do ‘pyrrole‐type’ nitrogens; solvent to solute hydrogen bonding is the dominant contribution to the changes in shielding for the ‘pyridine‐type’ nitrogen atoms as the solvent is varied. Solvent polarity effects are important for both types of nitrogen atom in azaindolizines and can be attributed to a solvent‐induced electronic charge separation between the nitrogen atoms concerned.Quantum chemical calculations involving the solvaton model are used to provide supporting evidence for the importance of solvent polarity effects on nitrogen shieldings in azaindolizines.

A13C and15N NMR study of some furoxans and related compounds

Carbon and nitrogen NMR results are reported for a collection of furoxans and related compounds, taken on DMSO solutions. The15N chemical shifts and those of neighboring13C nuclei have characteristic values for the structures studied. Relative14N signal widths are used to identify the nitro group resonances. Valence tautomerism at room temperature is reported for one compound. The INADEQUATE technique is used to determine some1J(13C-13C) data.

Assignment of All Proton, Carbon, and Nitrogen NMR Signals of Antamanide in Chloroform Solution

AbstractHomo‐ and heteronuclear one‐ and two‐dimensional techniques have been used to assign the 1H, 13C, and 15N NMR spectra of the cyclic decapeptide antamanide (1) in CDCl3. The assignment includes the aromatic resonances of phenylalanine and the non‐protonated nitrogen atoms of proline by means of heteronuclear two‐dimensional NMR spectroscopy. Sequence analysis of the four phenylalanine and four proline amino acid residues was performed by heteronuclear proton – carbon long‐range couplings using the COLOC sequence. Three new thiazolidine analogues of antamanide confirm the sequence analysis of prolines and open the possibility for the extraction of extended spectral parameters. The interpretation of NOE data, obtained from one‐ and two‐dimensional spectra at high field and low temperatures, demonstrate possible misinterpretations of this effect respecting sequence assignment, if only NOEs between NH protons and α‐protons are considered.

Effects of solute–solvent interactions on the nitrogen nuclear shieldings of some alkyl cyanides

AbstractIt was found that the range of solvent effects on the nitrogen NMR shielding of the cyano group appears to be almost independent of the nature of the attached alkyl group and to be in excess of 20 ppm. Effects due to both the polarity of the medium and hydrogen bonding are observed to contribute almost equally to the nitrogen shielding ranges measured for four alkyl cyanides. These contributions are determined from the shielding in nitrogen variations with the solvent by means of a four‐parameter model and are supported by molecular orbital calculations employing the solvaton description of non‐specific solute‐solvent interactions. The observed responses of the nitrogen shieldings to solvent effect are found to be significantly different from those reported for sp2‐type nitrogen atoms.

Nitrogen NMR studies on some fused ring N-heterocycles

^(15)N and^(14)N NMR data are reported for a number of fused ring N-heterocycles.^(14)N line widths,^(15)N-^1H couplings and nitrogen shielding additivity rales are used for^(15)N signal assignments. The results obtained lead to some progress in the generalization of the effects of nitrogen-nitrogen interactions on nitrogen shieldings.

Structural studies on some mesoionic compounds using nitrogen NMR

Abstract1H, 13C, 14N and 15N NMR data are reported for two 1,2,3,4‐oxatriazolium‐5‐thiolates and for two 1,2,3,4‐thiatriazolium‐5‐olates. It is demonstrated that nitrogen NMR is the most sensitive technique for determining the structures of these mesoionic compounds; of particular significance is the N‐2 chemical shift, which distinguishes between the presences of either oxygen or sulphur in position 1. Cyclic structures are confirmed for these compounds on the basis of the nitrogen chemical shifts.

New block copolymers V. Synthesis, characterization and morphological studies of poly(pentamethylene terephthalate)-b-(acrylonitrile butadiene rubber)

A block copolymer was prepared by low temperature polycondensation between (acid chloride)-terminated poly(pentamethylene terephthalate) as the hard block, and amine-terminated acrylonitrile-butadiene rubber, as the soft block. The polymer was characterized by nitrogen analysis, IR and NMR spectroscopy. The polymer showed two glass transition temperatures (Tg) and exhibited two-phase morphology.

ChemInform Abstract: Magnetic Properties in Terms of Localized Quantities. Part 7. Application to Nitrogen NMR Shifts

ChemInformVolume 19, Issue 3 Physical Organic Chemistry ChemInform Abstract: Magnetic Properties in Terms of Localized Quantities. Part 7. Application to Nitrogen NMR Shifts M. SCHINDLER, M. SCHINDLER Lehrstuhl Theor. Chem., Ruhr-Univ. Bochum, D-4630 BochumSearch for more papers by this author M. SCHINDLER, M. SCHINDLER Lehrstuhl Theor. Chem., Ruhr-Univ. Bochum, D-4630 BochumSearch for more papers by this author First published: January 19, 1988 https://doi.org/10.1002/chin.198803050Read 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 onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume19, Issue3January 19, 1988 RelatedInformation

ChemInform Abstract: Formation and Nitrogen NMR Spectra of Some Nitrimines (′Pernitroso‐ketones′), and the Mechanism of Oxime Cleavage by Nitrous Acid.

AbstractThe formation of nitrimines, by the action of nitrous acid on oximes, is shown to proceed without scrambling of the nitrogen atoms, the oxime nitrogen forming the imine, and the nitrous acid generating the nitro group.

Magnetic properties in terms of localized quantities. 7. Application to nitrogen NMR shifts

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMagnetic properties in terms of localized quantities. 7. Application to nitrogen NMR shiftsMichael SchindlerCite this: J. Am. Chem. Soc. 1987, 109, 20, 5950–5955Publication Date (Print):September 1, 1987Publication History Published online1 May 2002Published inissue 1 September 1987https://doi.org/10.1021/ja00254a009RIGHTS & PERMISSIONSArticle Views109Altmetric-Citations38LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (736 KB) Get e-Alerts Get e-Alerts

Hydrogen and nitrogen NMR chemical shifts of pentaamminecobalt(III) complexes: correlations with parameters calculated from ligand field spectra

Hydrogen and nitrogen NMR chemical shifts of pentaamminecobalt(III) complexes: correlations with parameters calculated from ligand field spectra

ChemInform Abstract: High‐Resolution 14N Overtone Spectroscopy: An Approach to Natural Abundance Nitrogen NMR of Oriented and Polycrystalline Systems.

Chemischer InformationsdienstVolume 17, Issue 42 Physical Organic Chemistry ChemInform Abstract: High-Resolution 14N Overtone Spectroscopy: An Approach to Natural Abundance Nitrogen NMR of Oriented and Polycrystalline Systems. R. TYCKO, R. TYCKOSearch for more papers by this authorS. J. OPELLA, S. J. OPELLASearch for more papers by this author R. TYCKO, R. TYCKOSearch for more papers by this authorS. J. OPELLA, S. J. OPELLASearch for more papers by this author First published: October 21, 1986 https://doi.org/10.1002/chin.198642044Read 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 onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume17, Issue42October 21, 1986 RelatedInformation

High-resolution nitrogen-14 overtone spectroscopy: an approach to natural abundance nitrogen NMR of oriented and polycrystalline systems

In this paper, the authors present a novel approach to nitrogen NMR spectroscopy of both oriented and polycrystalline samples. The method employs the direct excitation and detection of /sup 14/N overtone NMR transitions at approximately twice the /sup 14/N Larmor frequency. New approaches to nitrogen NMR are needed both because of the chemical and biochemical importance of nitrogen and because of the limitations of current methods. In the solid state, /sup 15/N NMR typically requires isotopic labeling to achieve sufficient sensitivity. Through cross-polarization, good sensitivity is achieved in /sup 14/N NMR of single crystals. The large quadrupole interactions of /sup 14/N nuclei provide high resolution in single-crystal spectra but at the expense of a spectral width of several megahertz. Since the experimentally observable spectral range is only about 200 kHz, it is impossible to acquire a complete spectrum without repeated returning of the spectrometer. /sup 14/N powder pattern spectra have only been obtained with indirect detection or when the quadrupole couplings are unusually small. Large quadrupole couplings also limit the applicability of double-quantum and zero-field NMR techniques. For these reasons, the authors become interested in the insightful proposal by Bloom, and the experimental demonstration by Legros and Bloom, that /supmore » 14/N overtone NMR transitions can be directly excited and detected in the solid state.« less

A theoretical and empirical approach to solvent effects on nitrogen nuclear shielding

AbstractSolvent effects on nitrogen shieldings are shown to vary from almost zero to about 26 ppm. These shielding variations can be analysed in terms of a variety of hydrogen bonding interactions and non‐specific solute–solvent interactions. Steric effects are also taken into account. The non‐specific interactions are found to be well accounted for by INDO/S‐SOS shielding calculations incorporating the solvaton model. Nitrogen NMR is shown to be very suitable for distinguishing between a variety of solute–solvent interactions.

New block copolymers. 1. Synthesis and characterization of an (a–b)n type block copolymer

AbstractA new (A–B)n type block copolymer has been synthesized by polycondensation of acidchloride terminated poly(ethylene‐terephthalate) with amine‐terminated butadiene acrylonitrile rubber (ATBN). The acid chloride terminated poly(ethylene‐terephthalate) was synthesized by reacting terephthaloyl chloride with ethylene glycol using N,N‐dimethyl formamide as the solvent. The resulting polymer was characterized by nitrogen analysis, IR and NMR spectroscopy. The solubility characteristics, solution viscosity behaviour, crystallinity, and phase characteristics of the polymer have been studied.

Nitrogen NMR and molecular interations

Nitrogen NMR and molecular interations

On the polymerization of acrylamide in methanol in presence of poly(ethylene glycol)

AbstractAcrylamide was polymerized in presence of poly(ethylene glycol)‐200 (PEG), with persulphate as initiator, in methanol as reaction medium, with varying monomer concentrations. The polymers obtained were finely divided powders and readily soluble in water, unlike pure polyacrylamide. The incorporation of PEG into the polymers was demonstrated by nitrogen determination, IR, and NMR studies. PEG does not covalently link to the polyacrylamide chains, but forms a blend with the polymer.

Motion of the nitrate ion in the solid I and II phases of ammonium nitrate using nitrogen NMR

In the solid I phase of NH 4NO 3, nitrogen-14 NMR spectroscopy indicates that the nitrate ion is undergoing rapid overall rotations, τ 2 ⋍ 8.3 ps at 140°C. In the solid II phase the rotations of the nitrate ion are probably restricted to in-plane C 3 rotations.

Free‐radical copolymerizations of N‐arylmaleimides. II

AbstractFree‐radical copolymerization of methyl acrylate (MA) with N‐p‐chlorophenylmaleimide (NPCMI) and N‐p‐bromophenylmaleimide (NPBMI) initiated by AIBN in cyclohexanone solution at 75°C was studied. The copolymer composition has been determined from the nitrogen content and NMR spectra of the copolymers. The reactivity ratios have been calculated by ML, FR, KT, and JJ methods. Q and e values of NPCMI and NPBMI have also been calculated by the Alfrey–Price Q‐e scheme.