Chemical Shifts Of Ring Protons Research Articles

1H NMR Spectroscopy of Dopamine Interacting with Lipid Vesicles

Dopamine, a naturally occurring neurotransmitter, plays an important role in the brain's reward system, and acts on sensory receptors in the brain. Neurotransmitters are contained in lipid membraned vesicles, and are released by exocytosis. All neurotransmitters interact with transport and receptor proteins in glial cells, on neuronal dendrites, and at the axonal button, and also must interact with membrane lipids. However, the extent of direct interaction between lipid membranes in the absence of receptors and transport proteins has not been extensively investigated. A recently developed NMR method uses an equivalent isopropanol concentration (EIC) scale to describe the interaction of aromatic moieties with lipid membranes as demonstrated for aromatic side chains of amino acid residues [1]. In this method, a range of isopropanol concentrations is used to provide a reference scale for hydrophobic interactions. Therefore, similar UV and NMR measurements were made with dopamine dissolved into varying concentrations of isopropanol to establish a standard EIC curve for measurement of dopamine interactions with lipid membranes. UV spectroscopy shows a maximum absorbance range around 286.6 - 288.2 nm and 1H NMR spectroscopy shows a progressive shift of aromatic ring proton chemical shifts towards higher field as the concentration of isopropanol increases. Next, dopamine was mixed with sonicated unilamellar DOPS vesicles and with sonicated unilamellar DOPC vesicles to measure its affinity and orientation in each type of vesicles. The measured EIC maps show that dopamine interacts differently with PC and PS lipids consistent with the fact that the positively charged dopamine experiences an electrostatic attraction for negatively charged PS lipids. This suggests that the extent of dopamine release could depend on lipid composition. [1] Johnson et al., Journal of Membrane Biology, 248, 695-703, 2015.

Synthesis, spectral studies and antimicrobial activities of some 2-naphthyl pyrazoline derivatives

A series of 2-naphthyl pyrazolines were synthesized by the cyclization of 2-naphthyl chalcones and phenylhydrazine hydrochloride in the presence of sodium acetate. The yields of pyrazoline derivatives are more than 80%. The synthesized pyrazolines were characterized by their physical constants, IR, 1H, 13C and MS spectra. From the IR and NMR spectra the CN (cm−1) stretches, the pyrazoline ring proton chemical shifts (ppm) of δHa, Hb and Hc and also the carbon chemical shifts (ppm) of δCN are correlated with Hammett substituent constants, F and R, and Swain–Lupton’s parameters using single and multi-regression analyses. From the results of linear regression analysis, the effect of substituents on the group frequencies has been predicted. The antimicrobial activities of all synthesized pyrazolines have been studied.

Solvent-oriented 1H NMR chemical shifts of pyridinium iodide and application of Buckingham equation

1H NMR studies of 1-ethyl-4-carbomethoxypyridinium iodide (Py +I −) have been carried out in various neat solvents with a dielectric constant range of 4.81–78.4. The effect of solvents on the chemical shifts of pyridinium ring protons ( δ 2,6 and δ 3,5) have been studied to envisage and understand the interactions of positively charged pyridinium ring with the solvents. These interactions were found to decrease with the increase in solvent polarity. The solute parameters which are responsible for interactions with a polar solvent were calculated from the slopes and intercepts of Buckingham equation plots. A comparison in terms of solvent polarity parameters; the dielectric constant ( ε) and the dielectric function ( η) upon the above mentioned interaction was carried out which showed that the iodide ion (I −) is tilted more with increasing polarity of the solvent than being exactly perpendicular to the Py + ring. The observed linear variation of δ 2,6 and Δ δ (the difference between the chemical shifts of ring protons, Δ δ = δ 2,6 − δ 3,5) with various solvent polarity parameters, suggests that Δ δ-values of Py +I − can be used as solvent polarity parameter in a similar fashion as Z-values. It may be more applicable in solvent selection during simultaneous organic synthesis and NMR analysis.

Computing the 1H NMR Spectrum of a Bulk Ionic Liquid from Snapshots of Car–Parrinello Molecular Dynamics Simulations

We have investigated the performance of several computational protocols in predicting the NMR spectrum of a molecular ion in a complex liquid phase such as an ionic liquid. To do this, we computed the proton NMR chemical shifts of the 1-ethyl-3-methylimidazolium cation [emim](+) in [emim][Cl]. Environmental effects on the imidazolium ring proton chemical shifts are quite significant and must be taken into account explicitly. Calculations performed on the isolated imidazolium cation as well as on the [emim][Cl] ion pair grossly fail to reproduce the correct spacing between proton signals. In contrast, calculations performed on clusters extracted from the trajectory of a Car-Parrinello molecular dynamics simulation yield very good results.

Preparations of regioselectively methylated cellulose acetates and their 1H and 13C NMR spectroscopic analyses

AbstractSeven possible regioselectively methylated cellulose acetates (RS‐MCAs)—2,3,6‐tri‐O‐methyl cellulose acetate, 3,6‐di‐O‐methyl cellulose acetate, 2,6‐di‐O‐methyl cellulose acetate, 2,3‐di‐O‐methyl cellulose acetate, 6‐O‐methyl cellulose acetate, 3‐O‐methyl cellulose acetate, and 2‐O‐methyl cellulose acetate—were prepared for the first time from chemically synthesized cellulose derivatives obtained by cationic ring‐opening polymerization and then were analyzed by 1H and 13C NMR spectroscopy. The chemical shifts of ring protons and carbons were influenced by substituent groups (methyl or acetyl) and clearly reflected the pattern of substituent distribution in anhydroglucose units. These data may conveniently be used for the determination of the substituent distribution of methyl cellulose. The synthesized RS‐MCAs also may be used for the elucidation of the structure–property relationship. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4167–4179, 2002

1H NMR and UV–Vis spectroscopy of chlorine substituted stilbenes: conformational studies

1H NMR and UV–Vis spectroscopic studies as well as molecular mechanics calculations have been performed for the trans and cis isomers of a series of chlorine substituted stilbenes (2–10). Correlations are found between the predicted molecular conformations and various NMR and UV–Vis spectroscopic parameters, indicating that these are suitable for conformational studies. The ethylene proton chemical shifts, in particular, are found to be sensitive to anisotropy effects of the nearby C–Cl bonds. Both ethylene and some ring proton chemical shifts are found to be dependent on the ring current effects, which are substituent and ring orientation dependent. UV spectra support the structural predictions based on the molecular mechanic vs. NMR correlation analysis. Average minimum energy conformations of compounds 1–10 are given in the paper.

Proton NMR study of triantennary complex type N-linked glycan chains: assignment of proton chemical shifts of the beta-Man residue in a basic unit of the triantennary glycan chain having a GlcNAc beta 1-->6 Man alpha 1-->6 Man beta-->sequence.

The chemical shifts of ring protons of the beta-Man residue in a triantennary complex type N-linked glycan chain having a GlcNAc beta 1-->6(GlcNAc beta 1-->2)Man alpha 1-->6 Man beta sequence were unambiguously determined by two-dimensional proton nuclear magnetic resonance (1H-NMR) spectroscopic methods. The chemical shift of H4 (3.84 ppm) of the beta-Man residue was for the first time revealed to be different from those (approximately 3.77 ppm) of biantennary and alternative type of triantennary glycans having a GlcNAc beta 1-->2 Man alpha 1-->6 Man beta sequence, but quite close to that (3.86 ppm) of a pentaantennary glycan containing a GlcNAc beta 1-->6 residue on the Man alpha 1-->6 Man beta sequence. Thus, the addition of GlcNAc beta 1-->6 residue on the Man-4' residue, whose formation is catalyzed by GlcNAc transferase V, is considered to cause a down-field shift of beta-Man H4 in the complex-type N-glycan chains. One possible explanation of this phenomenon is that the conformation of Man alpha 1-->6 arm is folded back toward the proximal core region, as is the case with the complex-type N-glycan chains with the bisecting GlcNAc residue.

A precise analysis of the 1H nuclear magnetic resonance spectrum of 2-phenyl-1,3-dithiane. Ring pucker, signs of long-range J(H,H), internal rotational barrier, and van der Waals shifts

The 1H nuclear magnetic resonance spectrum of 2-phenyl-1,3-dithiane, as a dilute solution in a CS2–C6D12–TMS solvent mixture at 300 K, is analyzed to yield 8 chemical shifts and 22 distinct coupling constants, nJ(H,H), n = 2–6. The coupling constant between H-2 and the para proton indicates, first, that the bisected conformer (phenyl plane perpendicular to the pseudo plane of the dithiane ring) is most stable and, second, that the apparent twofold barrier to rotation about the Csp2—Csp3 bond is 9.6 kJ/mol. The AM1, STO-3G, and STO-3G* computations confirm the twofoldedness of the barrier; the AM1 barrier is 9.4 kJ/mol. The empirical equation, [Formula: see text] reproduces the vicinal coupling constants of the CH2CH2CH2 fragments and implies puckering angles [Formula: see text] of 54°, 61°, and 64°, respectively. It is implied that 3J at [Formula: see text] is larger than at [Formula: see text] This results is discussed in terms of the latest theoretical approach to 3J in the HCCH fragment. The 4J(H,H) signs and magnitudes for the CH2CH2CH2 fragment agree reasonably well with theory. For the CH2SCH fragment, 4J(H,H) values are positive, in contrast to corresponding numbers in the propanic fragment, perhaps the first experimental values for certain rigid orientations about a heteroatom. INDO MO FPT computations on propane, dimethyl ether, and dimethyl sulfide confirm the experimental trend in 4J(H,H). 2J(H,H) and 5J(H,H) values are compared to those in related molecules. The striking differential shifts of the axial and equatorial protons are attributed to differential van der Waals interactions with the 3p lone-pair orbital on sulfur. A comparison of the ring proton chemical shifts with those in phenylcyclohexane and isopropylbenzene implies that C—S bonds are weaker net electron donors by hyperconjugation than are C—C bonds. It is also proposed that the ortho protons are deshielded by intramolecular van der Waals interactions with the 3p orbitals on the sulfur atoms.

Study of hydrogen bonding in 1-ethyl-2-methyl-4-oxo-1,4-dihydro-pyridin-3-yloxyethanoic acid and 3-(1,2-diethyl-4-oxo-1,4-dihydropyridin-3-yloxy)propanoic acid by 1H NMR spectroscopy and X-ray crystallography

A series of 1,2-dialkyl-4-oxo-1,4-dihydropyridin-3-yloxyethanoic acids and 3-(1,2-dialkyl-4-oxo-1,4-dihydropyridin-3-yloxy)propanoic acids have been synthesized via the corresponding pyran-4-ones. Ring proton chemical shifts indicate hydrogen bonding between the side-chain carboxylic acid proton and the 4-oxo group of the heterocycle to be present only for the pyridinone species in DMSO solution. X-Ray crystallography demonstrates the hydrogen bonding in 1 -ethyl-2-methyl-4-oxo-1,4-dihydropyridin-3-yloxyethanoic acid to be very strong (O—O = 2.441 A) and intramolecular, giving a unique 8-membered chelate ring. The analogous hydrogen bonding in 3-(1,2-diethyl-4-oxo-1,4-dihydropyridin-3-yloxy)propanoic acid is however strong (O—O = 2.541 A) and inter-molecular, giving an infinite structure.

Substituent effect on ring proton chemical shifts in PMR spectra of monosubstituted pyridines

The relative chemical shifts of ring protons in PMR spectra of 2-, 3-, and 4-monosubstituted pyridines (in DMSO-D6) are correlated with the F- and R-constants of the substitutents by using a two-parameter approach. Transmission factors characterizing the transfer of inductive and resonance effects in pyridine, pyrimidine, and s-triazine rings are analyzed.

Proton nuclear magnetic resonance characterization of the aromatic residues in the variant-3 neurotoxin from Centruroides sculpturatus Ewing.

The amino acid sequence for the variant-3 (CsE-v3) toxin from the venom of the scorpion Centruroides sculpturatus Ewing contains eight aromatic residues. By use of 2D NMR spectroscopic methods, the resonances from the individual protons (NH, C alpha H, C beta H',H", and the ring) for each of the individual aromatic residues have been completely assigned. The spatial arrangement of the aromatic ring systems with respect to each other has been qualitatively analyzed by 2D-NOESY techniques. The results show that Trp-47, Tyr-4, and Tyr-42 are in close spatial proximity to each other. The NOESY contacts and the ring current induced shifts in the resonances of the individual protons of Tyr-4 and Trp-47 suggest that the aromatic ring planes of these residues are in an orthogonal arrangement. In addition, the spatial proximity of the rings in the pairs Tyr-4, Tyr-58; Tyr-42, Tyr-40; and Tyr-40, Tyr-38 has also been established. A comparison with the published crystal structure suggests that there is a minor rearrangement of the aromatic rings in the solution phase. No 2D-NOESY contacts involving Phe-44 and Tyr-14 to any other aromatic ring protons have been observed. The pH dependence of the aromatic ring proton chemical shifts has also been studied. These results suggest that the Tyr-58 phenolic group is experiencing a hydrogen-bonding interaction with a positively charged group, while Tyr-4, -14, -38, and -40 are experiencing through-space interactions with proximal negatively charged groups. The Trp-47 indole NH is interacting with the carboxylate groups of two proximal acidic residues. These studies define the microenvironment of the aromatic residues in the variant-3 neurotoxin in aqueous solution.

Isolation and Identification of the Major Component of Setal Exudate from Corythucha ciliata

Isolation and Identification of the Major Component of Setal Exudate from Corythucha ciliata

1H nuclear magnetic resonance spectral parameters of toluene. Implications for conformational analysis and isotope shifts

A precise analysis of the 1H nmr spectrum of toluene as a dilute solution in carbon disulfide yields a revised set of spectral parameters. The chemical shift of the para proton lies 12.6 ppb to low frequency of that of the ortho protons at 300 K. The ring proton chemical shifts are discussed and compared with 1H and 3H shifts observed in carbon tetrachloride. The long-range couplings between methyl and ring protons can be said to be quantitatively understood in terms of σ and σ–π electron transmitted mechanisms. The changes observed in these three couplings in phenylacetaldehyde can be quantitatively reproduced in terms of these mechanisms and also illustrate how these changes are direct measures of the conformational preferences in this molecule.

1H NMR Study of Methyl O-Acetyl-α-and-β-D-Xylopyranosides Conformational Studies and Non Additivity of1H-Shift Increments

Abstract 1H NMR spectra of the complete series of fully and partially acetylated methyl α-and β-D-xylopyranosides have been studied. The α-anomers occur exclusively in 4C1 chairs but the 1C4 chair becomes increasingly populated in the β-forms especially when the OH-3 is not acetylated. Increments used for the prediction of the chemical shifts of ring protons are discussed and compared with the literature data. The predictability for changes in shifts upon acetylation is poor.

NMR study of proton transfer interactions in the system pyridine +HCl (0%–95%)

Pyridinium chloride, which has proven useful in a number of molten salt studies where it serves as a strong chloride donor Lewis base, is freely soluble in both excess acid and excess base. To probe the proton transfer interactions involved, proton NMR studies have been performed on pyridine+HCl solutions in the composition range 0%–95% HCl at temperatures ranging from −100°C to 200°C. This system is rich in examples of the way in which competing hydrogen bonding interactions can affect the magnetic environment of the involved protons. The most obvious of these is the increased magnetic shielding that develops in the vicinity of the N–H+ proton of the pyridinium cation as excess HCl competes for the Cl− ions, initially to form HCl2− anion and later to form more extended HCl⋅⋅⋅HCl−2 aggregates. As excess pyridine is added to PyHCl a shift in the opposite direction occurs, due either to the formation of symmetrical [Py–H–Py]+ species, to the repression of PyHCl autodissociation, or to a combination of both effects as expressed by (PyHCl)2 dimer formation. Less obvious but equally interesting is the deshielding of the proton in the HCl2− anion of the PyH+–HCl2− melt which accompanies addition of pyridine. This results from a competition between Py with Cl− for the HCl proton and a consequent tendency to produce the [PyH⋅⋅⋅Cl⋅⋅⋅HPy]+ species implied by the stoichiometry of certain crystalline compounds. Finally the ring protons themselves reflect the competition of excess HCl for the Cl− of PyHCl and the consequent shifts in ring electron density which accompany the inward movement of the N–H+ proton. The trends are such as to bring the observed ring proton chemical shifts relative to pyridine into better accord with theoretical predictions for the isolated PyH+ cation. The trend is continued when excess HCl is replaced by the stronger Lewis acids ZnCl2 and AlCl3 and in the case of excess AlCl3, agreement with theory is almost quantitive except for the α proton shifts. For the latter, the observed shifts are not even qualitatively correct.

ChemInform Abstract: HIGH‐PRESSURE HIGH‐RESOLUTION NUCLEAR MAGNETIC RESONANCE. PRESSURE DEPENDENCE OF THE RING PROTON CHEMICAL SHIFTS OF SUBSTITUTED BENZENES

Chemischer InformationsdienstVolume 8, Issue 33 Physical Organic Chemistry ChemInform Abstract: HIGH-PRESSURE HIGH-RESOLUTION NUCLEAR MAGNETIC RESONANCE. PRESSURE DEPENDENCE OF THE RING PROTON CHEMICAL SHIFTS OF SUBSTITUTED BENZENES H. YAMADA, H. YAMADASearch for more papers by this authorC. ITANI, C. ITANISearch for more papers by this authorK. OTSUKA, K. OTSUKASearch for more papers by this author H. YAMADA, H. YAMADASearch for more papers by this authorC. ITANI, C. ITANISearch for more papers by this authorK. OTSUKA, K. OTSUKASearch for more papers by this author First published: August 16, 1977 https://doi.org/10.1002/chin.197733049AboutPDF 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. Volume8, Issue33August 16, 1977 RelatedInformation

High-pressure high-resolution nuclear magnetic resonance. Pressure dependence of the ring proton chemical shifts of substituted benzenes

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHigh-pressure high-resolution nuclear magnetic resonance. Pressure dependence of the ring proton chemical shifts of substituted benzenesHiroaki Yamada, Chiharu Itani, and Kazuko OtsukaCite this: J. Am. Chem. Soc. 1977, 99, 11, 3572–3575Publication Date (Print):May 1, 1977Publication History Published online1 May 2002Published inissue 1 May 1977https://doi.org/10.1021/ja00453a006RIGHTS & PERMISSIONSArticle Views43Altmetric-Citations12LEARN 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 (523 KB) Get e-Alerts Get e-Alerts

Experimental and theoretical study of the induced paramagnetic ring-current in the 4-membered ring of biphenylene and related hydrocarbons

Ring current intensities and proton chemical shifts have been calculated for a series of condensed aromatic hydrocarbons including biphenylenes. The calculations show that an induced paramagnetic ring current occurs in the 4-membered ring of each of the biphenylenes studied and this effect accounts for the observed spectra. PMR measurements on 1-mono-, 2-mono- and 2,3,6,7-tetra-deuteriated biphenylene prove that the chemical shifts of the 1- and 2-protons are at δ CDCl 3 6.60 and 6.70 respectively and not vice versa as assumed by previous authors.

Substituent effects on the ring proton chemical shifts in iodomethylbenzenes

Substituent effects on the ring proton chemical shifts in iodomethylbenzenes

Proton Spin–Spin Coupling Constants in Isothiazole, Isoxazole, and some of their Alkyl Derivatives

The signs and magnitudes of the spin–spin coupling constants over three to six bonds between protons in isothiazole, isoxazole, and in 10 of their alkyl derivatives are measured and discussed in terms of the coupling mechanisms. The chemical shifts of ring protons and methyl protons appear to arise from a common mechanism originating in the ring but are not simply related to electron densities calculated by molecular orbital theory at the CNDO/2 level of approximation.