Proton Spin Coupling Research Articles

Hydrogen bonding of the hydroxyl group and spin—spin coupling of the ring protons of substituted phenols

The chemical shifts and coupling constants of the hydroxyl and ring protons of the following substituted phenols and anisoles have been obtained in basic and nonbasic solvents: 2-adamant-1-yl-4-tert-butylphenol, 6-bromo-2-adamant-1-yl-4-tert-butylphenol, 3,5-di-tert-butylphenol, 3,5-dichlorophenol, 6-bromo-2-adamant-1-yl-4-tert-butyl anisole and 6-bromo-2,4-di-tert-butyl anisole. Hydrogen bonding of the hydroxyl group of the substituted phenols to the solvent does not cause any detectable change in the spin—spin coupling between the meta protons, but causes a very small increase (<0.10 Hz) in the coupling between the ortho and para protons.

Assignment and conformational properties of the exocyclic 5′-hydroxy-methyl group of nucleosides by nuclear magnetic resonance spectroscopy

The assignment of the methylene protons of the exocyclic group of nucleosides has been confirmed by comparison of the H(5′) chemical shifts of corresponding 2′- and 3′-nucleotides and by direct observation of hydrogen bonding between the 5′-hydroxy- and 2-keto-groups of N(3)-methyl-2′,3′-O-isopropylideneuridine in CDCl3 and CCl4 solutions. The assignment of the methylene protons permits calculation of the relative populations of the three C(4′)–C(5′) bond rotamers. The results are consistent with crystal structure analyses of β-nucleosides, i.e. gg > gt > tg. An analysis of the contributions to vicinal proton spin coupling constants and chemical shifts of the exocyclic hydroxymethyl group together with the correct signal assignment confirms the approximate correlation between the sum of proton spin coupling constants and the chemical shift differences between the methylene protons of pyrimidine nucleosides. The method is extended to purine nucleosides.

ChemInform Abstract: (1)H NUCLEAR MAGNETIC RESONANCE STUDY OF THE SMALL CLOSO‐CARBORANES 1,5‐DICARBA‐CLOSO‐PENTABORANE(5), CARBA‐CLOSO‐HEXABORANE(7), 1,2‐DICARBA‐CLOSO‐HEXABORANE(6), 1,6‐DICARBA‐CLOSO‐HEXABORANE(6), AND 2,4‐DICARBA‐CLOSO‐HEPTABORANE(7)

Chemischer InformationsdienstVolume 5, Issue 22 Organoelement Compounds ChemInform Abstract: (1)H NUCLEAR MAGNETIC RESONANCE STUDY OF THE SMALL CLOSO-CARBORANES 1,5-DICARBA-CLOSO-PENTABORANE(5), CARBA-CLOSO-HEXABORANE(7), 1,2-DICARBA-CLOSO-HEXABORANE(6), 1,6-DICARBA-CLOSO-HEXABORANE(6), AND 2,4-DICARBA-CLOSO-HEPTABORANE(7) THOMAS ONAK, THOMAS ONAKSearch for more papers by this authorEMMA WAN, EMMA WANSearch for more papers by this author THOMAS ONAK, THOMAS ONAKSearch for more papers by this authorEMMA WAN, EMMA WANSearch for more papers by this author First published: June 4, 1974 https://doi.org/10.1002/chin.197422321AboutPDF 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. Volume5, Issue22June 4, 1974 RelatedInformation

1H nuclear magnetic resonance study of the small closo-carboranes 1,5-dicarba-closo-pentaborane(5), carba-closo-hexaborane(7), 1,2-dicarba-closo-hexaborane(6), 1,6-dicarba-closo-hexaborane(6), and 2,4-dicarba-closo-heptaborane(7)

Boron-11 decoupled proton n.m.r. spectra and data are reported for the closo-carboranes 1,5-C2B3H5, CB5H7, 1,2-C2B4H6, 1,6-C2B4H6, and 2,4-C2B5H7. The 1H n.m.r. results are in agreement with the structural assignments for these carboranes and are compatible with previously obtained boron-11 n.m.r. results. Fine structure, attributed to homonuclear long-range coupling, is observed in the decoupled spectrum of each of these closed polyhedral compounds. The largest long-range proton–proton spin coupling (10–12 Hz) is found between trans situated nuclei in 1,5-C2B3H5, CB5H7, and in 1,2-C2B4H6. An estimate of orbital hybridization in C2B3H5 from 11B13C, H13C, and H11B coupling data indicates that most of the cage-orbital s-character is to be found in the C–B bonds and very little in the B–B bonds. Unambiguous chemical shift assignments are made for all the proton resonances except for the 2,3 and 4,5 positions of CB5H7.

Determination of the conformation of peptide and n-methylated peptide bonds by observation of 5j(hh) proton spin-coupling using nmdr spectroscopy

Determination of the conformation of peptide and n-methylated peptide bonds by observation of 5j(hh) proton spin-coupling using nmdr spectroscopy

Dirac vector model and variational treatments of proton spin-spin coupling across three bonds

The Dirac vector model and variational treatments have been used to study the angular dependence of proton spin couplings across three bonds in fragments of the type H-X-Y-H (X, Y = C, N, O). These couplings can be expressed by means of the relation J(φ) = A + B cos φ + C cos2 φ, where φ is the dihedral angle and A, B and C are constants. It is seen that the behaviour of various fragments towards substituents can be qualitatively predicted by looking at the sign of the constant B.

High-resolution nuclear magnetic resonance evidence of conformational preference at a solid interface

From a study of the effect of temperature and surface coverage on the proton–proton spin coupling constant, the conformational preference of 1,1,2-trichloroethane adsorbed on pyrogenic silica has been determined.

Spectroscopic studies of keto–enol equilibria. Part XIII.15N-substituted imines

Schiff bases have been synthesized from [15N]ammonia and 1-hydroxy-2-acetonaphthone, 2-hydroxy-1-naphthaldehyde, 5-methyl- and 4,5-dimethyl-acetophenones, 2-hydroxybenzophenone, benzoylacetone and 2-acetyl-5,5-dimethylcyclohexane-1,3-dione. The 1H n.m.r. and u.v. data permit assignment of tautomeric equilibria. The results indicate that the percentage of amide form is usually greater in these ammonia adducts than in the analogous methylamine or aniline derivatives. Proton–proton spin-coupling measurements provide important information concerning the electronic delocalization in the aromatic rings.

Empirical valence-force calculations of steroids—I : Conformations and relative energies of the 20-epimers of 5α-pregnane-3β,20-diol

Quantitative valence-force calculations (energy minimization by the Westheimer-Allinger-Boyd method) have been carried out on side chain conformers of both 5α-pregnane-3β,20-diols. The calculations allowed full relaxation of all internal coordinates of these steroids (comprising 59 atoms), but the large number of non-bonded interactions had to be reduced by imposing an arbitrary limit of 5 Å, bringing the total number of interactions (stretching, bending, torsion, non-bonded, 1,3, Coulomb) below the maximum load (1200) of the computer. Four rotamers of each diol, 20α and 20β, were examined differing with respect to the distribution of the groups about the bonds between C-17 and C-20 and between C-20 and oxygen. The results indicate that non-bonded strain between the side chain and the steroidal nucleus is largely accommodated by distortion of bond angles, but little by twisting of the groups about the C-17, C-20 bond. Two rotamers appear to predominate to a large extent in the conformational equilibrium of the 20β-epimer. Both forms have the hydrogen at C-20 anti to that at C-17 but differ in the OH orientation. In contrast the calculations for the 20α-epimer show that a substantial fraction occurs as an additional rotamer with a gauche distribution of the 17α- and 20-hydrogens. The published proton spin coupling constants agree well with the calculated results. A new interpretation, based on the existence of a conformational equilibrium is, therefore, offered to account for the published NMR data for the 20α-epimer. In addition “conformation instability contributions” of relevant side chain atoms have been calculated.

Proton Spin Coupling by Pi Electrons: Correction and Comments

Proton Spin Coupling by Pi Electrons: Correction and Comments

Conformation of non-aromatic ring compounds—XLVII : The conformation of trans-1,2-dihalogenoindans

Dipole moments, NMR, IR and Raman spectra of trans-1,2-dihalogenoindans were determined. Linear relations were found to exist between the squares of the dipole moments and the vicinal proton spin coupling constants. It is concluded that the diaxial conformer predominates in solution.

Conformation of non-aromatic ring compounds—XLIV : NMR spectra and dipole moments of some 2-substituted 1,3-dioxolanes

Proton spin coupling constants and chemical shifts (AA′BB′ part) in a number of 2-substituted 1,3-dioxolanes of the types: ▪ Combination of NMR and dipole amount data indicates rotation about the C2OR bond giving rise to an equilibrium between anti and gauche forms; the equilibrium constant depends on the bulk of group R. The mean phase angle of pseudorotation shifts slightly towards that of an envelope form, i.e. towards a smaller torsional angle of the CH 2CH 2 fragment, on passing from anti to gauche. From earlier X-ray data on bis-1,3-dioxolane 13 it is deduced that the maximum possible value of ϕ in 1,3-dioxolanes is about 30°; the actual value in the solid is 21°.

Correction. Proton Spin Coupling in 1-Indanone

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCorrection. Proton Spin Coupling in 1-IndanoneErnest Lustig and Edward RagelisCite this: J. Org. Chem. 1967, 32, 11, 3726Publication Date (Print):November 1, 1967Publication History Published online14 October 2003Published inissue 1 November 1967https://doi.org/10.1021/jo01286a626RIGHTS & PERMISSIONSArticle Views27Altmetric-Citations-LEARN 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 (124 KB) Get e-Alerts Get e-Alerts

Evidence for “through‐space” long‐range proton‐proton coupling in acetone

AbstractAccording to the theory of long‐range proton spin coupling by pi electrons, |JHH| in acetone should decrease with increasing polarity of the carbonyl group. Experimentally the opposite has been found. To explain the observed trend a “through‐space” mechanism is proposed. JHH is now interpreted as the result of a negative coupling by the pi electrons and a positive “through‐space” contribution. On this hypothesis a better fit numerically can also be obtained.

Proton spin coupling in four-membered rings—I. 2:2- d2-oxetane

Proton spin coupling constants for unsubstituted four-membered heterocyclics are unknown, and unravelling of their complex A 2B 4-type spectra is possible only with the aid of weak double irradiation. Thus, 2:2- d 2-oxetane was synthesized and all accessible NMR parameters were obtained from an analysis of the 4-proton band. Geminal coupling constants are in accord with predictions of the Pople and Bothner-By theory, and diagonal coupling constants are smaller than 0·3 Hz.

Nuclear-Magnetic-Resonance Spectra of Ureas in Aqueous Solution

There is considerable confusion in the literature concerning the nuclear-magnetic-resonance spectra of ureas in aqueous solution. Redpath and Smith report that the spectrum of N,N'-dimethylurea exhibits a broad signal for the protons on nitrogen and an unsymmetrical doublet for the methyl groups. This doublet collapses to a singlet in acid solutions and is attributed to spin–spin coupling of the methyl protons with the [Equation] moiety, rather than to any type of hindered rotation. Under similar conditions, Birchall and Gillespie report no observable coupling between the CH3− and =N–H groups of N,N'-dimethylurea, even in the absence of acid. This lack of spin–spin coupling is attributed to rapid proton exchange between the urea nitrogens and the solvent. They report no observable signal due to the =N–H moiety. However, the =N–H signal was found by them in the spectrum of urea itself under similar conditions.

Studies on Cyclic Polyols. V. Long-Range Proton Spin Coupling and Other Features of Nuclear Magnetic Resonance Spectra of Substituted Cyclopentanes1,2

Studies on Cyclic Polyols. V. Long-Range Proton Spin Coupling and Other Features of Nuclear Magnetic Resonance Spectra of Substituted Cyclopentanes^1,2

On the use of partly resolved structure for the analysis of NMR spectra. Application to the determination of the signs of the hydroxyl proton-ring proton nuclear spin coupling constants in substituted phenols

A series of frequency sweep nuclear magnetic double resonance experiments have been performed on 2-hydroxy-3-methoxybenzaldehyde; the strong irradiation field was applied to various parts in the ring proton band and the effects were observed in the hydroxyl band. The transition frequencies and transition probabilities in the double resonance spectra were calculated by numerical diagonalization of the double resonance Hamiltonian of the ABCX subsystem composed of the three ring protons and the hydroxyl proton. The large number of closely spaced transitions (eight transitions within an interval of less than 0.8 cps) necessitated a more detailed evaluation of the line-shapes. Superposition of eight Lorentzian resonance lines produced theoretical spectra in very good agreement with the observed ones and it was found that changes in transition frequencies amounting to a few hundredths of a cps produced significant changes in line-shape. The fact that such marginal effects can be employed for the evaluation of the spectra is attributed mainly to the high reproducibility of the experimental line-shape as obtained with NMR spectrometers employing internal proton stabilization. On the basis of the experiments one may deduce 1. (i) that the resolved spin coupling J OH-4 = 0.62 cps carries the same sign as the ring proton couplings and 2. (ii) that there exists an additional unresolved spin coupling J OH-6 = 0.13 ± 0.05 cps which also carries the same sign as the ring proton spin couplings. The general problems of sign determination of spin couplings and of the estimation of unresolved spin couplings are briefly discussed.

The stereochemical significance of the long-range proton spin coupling constant of the σ-fragment HCCCH

In the conformational analysis of organic compounds by proton magnetic resonance of fundamental importance is the dependence of the value of the proton-proton spin-spin coupling constant on the geometrical arrangement of the corresponding hydrogen atoms. This relationship has been quite thoroughly investigated for geminal and vicinal protons and is being extensively employed in conformational studies. On the other hand the no less important relations of the long-range proton spin coupling constant ( 4 J) through four sigma bonds (HCCCH) have been much less systematically investigated. In the present work the magnitudes and signs of 4 J have been determined in substituted tetrachlorobicyclo[2,2,1] heptanes, whose structural framework possesses sufficiently fixed angular parameters. The results from these model compounds have served as basis for an empirical correlation between 4 J and the dihedral angles of the fragment HCCCH, useful for structural purposes, and have also permitted an estimation of the contributions to the value of 4 J made by direct and indirect coupling of the protons.

Perturbation approach to the proton spin coupling in the ethane fragment

A general expression has been derived by perturbation theory for the long-range nuclear spin-spin coupling constant in a six-electron (three bond) system. This expression is used to evaluate the dependence of proton spin-spin coupling constant (J HH) on dihedral angle (Φ) in the ethane fragment.