Proton Resonance Spectra Research Articles

PROTON MAGNETIC RESONANCE MEASUREMENTS OF FORMAMIDE

The high-resolution proton resonance spectrum of formamide has been measured and analyzed. Quadrupole broadening of the resonance signals due to the N14 nucleus was eliminated by substitution of the isotopic nucleus N15. Twenty-four lines were resolved in the spectrum, which is consistent with restricted rotation about the C—N bond. The non-equivalence of the two protons in the N15H2 group is characterized by a smaller screening constant and a greater spin–spin interaction of the proton which is in the trans position relative to the carbonyl group. It is suggested this difference in the spin coupling of the two protons may be associated with different N—H bond lengths. Pronounced changes in the chemical shifts and spin-coupling constants result when formamide is dissolved in dilute solution in water and acetone. In water solution the relative magnitudes of the spin coupling of the two protons in the NH2 group is reversed from that observed in pure formamide and the coupling of the aldehyde proton to N15 varies by nearly 50%. Heating of formamide above room temperature causes rotation of the NH2 group as well as proton exchange between neighboring molecules. The two effects could be separated. From the observed changes in the proton spectra as a function of temperature the barrier hindering rotation (measured in a 10 mole% solution of formamide in acetone) was found to be 18 ± 3 kcal/mole. The activation energy for proton exchange in pure liquid formamide was found to be 10 ± 3 kcal/mole.

Solvent effects in the proton resonance spectra of dimethyl-formamide and dimethyl-acetamide

Changes in the nuclear magnetic resonance spectra of dimethyl-formamide and dimethyl-acetamide have been studied in various solvents over a range of concentrations. It is shown that addition of aromatic solvents causes the relative chemical shifts of the two methyl resonances to change sign. This shows that no rapid reorientation of the dimethyl amino group occurs in these solutions at room temperature, and the shifts observed are interpreted in terms of the formation of loose complexes between the amide and the aromatic molecule.

High resolution hydrogen resonance spectra of some substituted ethylenes

The olefinic proton resonance spectra of a number of mono- and 1, 2 di-substituted ethylenes have been analysed as AB, ABC or ABX systems to obtain the coupling constants and chemical shifts. The values of J trans (range observed 13·7 to 18·0 c/s in 14 compounds) were significantly larger than J cis in similar molecules. The values of J cis (range observed 6·5 to 12·3 c/s in 8 compounds) are abnormally large when the olefinic bond is conjugated to an aromatic ring. Coupling between adjacent protons in an olefinic methylene group (J gem) is much smaller, and sometimes negative. The shielding of the lone vinyl proton in mono-substituted ethylenes is smaller than that of the methylene group and in two cases (the vinyl group directly bonded to an oxygen atom) the difference is so great as to give an approximation to the ABX condition, so that the methylene protons appear to be shielded to an unusually large extent.

988. Proton resonance spectra of some 11-keto-steroids

988. Proton resonance spectra of some 11-keto-steroids

Spin-spin coupling constants in proton resonance spectra of acetylenes

Spin-spin coupling constants in proton resonance spectra of acetylenes

PHYSICAL PROPERTIES OF ALKYL PYRROLES AND THEIR SALTS

The structures of the ions formed by several alkyl pyrroles in hydrochloric acid are deduced from proton resonance spectra. Basicity values for three alkyl pyrroles are determined from ultraviolet spectra of their salts in buffer solutions. An attempt is made to estimate the basicity of other pyrroles from the variation of the—OD stretching frequency of methanol-d in solution in the pyrroles. Variations of the free and bonded NH frequencies of alkyl pyrroles are shown to be a simple function of the positions and number of the substituents.

Strong Coupling in Nuclear Resonance Spectra. III. Systems Containing Many Equivalent Spins

The spin-coupling problem is discussed for systems of p+q nuclei falling into two groups ApBq where all members of a group are magnetically equivalent. The energies are given explicitly for p=1, arbitrary q, and formulas are given from which the transition intensities can be computed for this case. The results are applied to the proton resonance spectrum of isobutane (p=1, q=9), with the results δCH3—δCH=0.85 ppm, ACH–CH3=6.8 cps.

Fine Structures of Proton Resonance Spectra of Fluorobenzene Derivatives

Fine Structures of Proton Resonance Spectra of Fluorobenzene Derivatives

Strong Coupling in Nuclear Resonance Spectra. I. The Five-Spin System of trans-Propenylbenzene

Energy levels and allowed transitions are calculated for a system of five spin-½ particles of the type ABX3. An extension to the more general system ABC3 is made by perturbation theory. The results are applied to an analysis of the proton resonance spectrum of trans-propenylbenzene, and it is found that at least one spin-spin coupling constant is negative. An ``anomalous'' spectrum previously reported, which shows superficial resemblances to the one studied here, is explained by assuming the presence of an impurity.

497. The broad-line proton resonance spectrum of iron carbonyl hydride

497. The broad-line proton resonance spectrum of iron carbonyl hydride

Proton resonance spectra of some gem-diols in the solid state

Proton resonance spectra of some gem-diols in the solid state

Proton Resonance Spectra and Structures of Mercury(II)-Olefin Addition Compounds

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTProton Resonance Spectra and Structures of Mercury(II)-Olefin Addition CompoundsF. A. Cotton and J. R. LetoCite this: J. Am. Chem. Soc. 1958, 80, 18, 4823–4826Publication Date (Print):September 1, 1958Publication History Published online1 May 2002Published inissue 1 September 1958https://doi.org/10.1021/ja01551a017RIGHTS & PERMISSIONSArticle Views37Altmetric-Citations21LEARN 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 (473 KB) Get e-Alerts Get e-Alerts

High-resolution proton and fluorine resonance spectra of para -fluoro-aniline

The proton and fluorine resonance spectra of liquid para -fluoro-aniline have been measured under resolving power of about 1 in 10 8 . The spectra are complicated, because the chemical shifts between the protons adjacent to the fluorine atom and those adjacent to the amino group are comparable with the various spin-coupling constants between the four protons and between the protons and the fluorine. The proton spectrum is of the type known as A 2 B 2 X , and an analysis for the energy levels and the 64 transitions is given. The proton and fluorine resonance spectra are interpreted in terms of this analysis, and the chemical shifts and spin-spin-coupling constants are determined.

Analysis of the proton nuclear magnetic resonance spectrum of formamide by the double resonance technique

The proton magnetic resonance spectrum of formamide, DCONH 2, HCOND 2 and HCONHD are analyzed, spin-spin couplings are determined. The method of analysis utilizes selective decoupling of the N 14 nucleus while observing the proton resonance. The complete relaxing of the N 14 nucleus eliminates the smearing effect of the electric quadrupole relaxation over the proton resonance spectrum.

High-resolution proton resonance spectra of some p-disubstituted benzenes

High-resolution proton resonance spectra of some p-disubstituted benzenes

Proton resonance spectra of some crystals containing nitrogen and fluorine

The preparation and analysis of a pure sample of ammonia-boron trifluoride is described. The proton and fluorine magnetic resonance spectra of this compound and also of ammonium fluorotitanate and ammonium fluorogermanate have been measured. The spectra from the fluorine nuclei at 90°K are consistent with a rigid arrangement of the fluorine nuclei in the lattice. The proton resonance spectra are, however, narrower than is possible in a rigid lattice structure and require reorientation of the NH 3 group and of the ammonium ions even at 20°K. This indicates a surprising weakness in the hydrogen bonds between the nitrogen and fluorine atoms. Other evidence which supports this conclusion is assembled in the discussion.

THE ANALYSIS OF NUCLEAR MAGNETIC RESONANCE SPECTRA: III. PYRIDINE AND DEUTERATED PYRIDINES

The proton resonance spectra of pyridine, 2,6-pyridine-d2, 3-pyridine-d1, and 4-pyridine-d1 have been obtained for the pure liquids under conditions of high resolution. The spectra have been analyzed as proton groupings of AB2X2, AB2, perturbed ABX, and B2X2 respectively. The spin-coupling constants obtained from analysis of the simpler spectra of the deuterated molecules were used to suggest trial solutions for the analysis of the complicated AB2X2 spectrum of pyridine. A final set of chemical shifts and spin-coupling constants derived for pyridine give satisfactory agreement between the observed and calculated spectrum.

THE ANALYSIS OF NUCLEAR MAGNETIC RESONANCE SPECTRA: II. TWO PAIRS OF TWO EQUIVALENT NUCLEI

This paper deals with the analysis of the nuclear magnetic resonance spectrum of two pairs of two equivalent nuclei (of spin [Formula: see text])whose relative chemical shift is of the same order as the spin-coupling constants of the system (A2B2 in the notation of Part I). The complete matrix is set up and correlated with the results of McConnell, McLean, and Reilly (4) for the corresponding theory with large chemical shiftsThe proton resonance spectrum of naphthalene is reported and is analyzed as an A2B2 system on the hypothesis that spin couplings between protons on different rings are negligible. A complete analysis of the spectrum of o-dichlorobenzene, which represents a further example of an A2B2, system, is also given. The spectrum of 1-chloro-2-bromoethane at room temperature is also analyzed as an A2B2 system.

Proton and Nitrogen Magnetic Resonance Spectra and Structure of Nitramide and Nitrourethane

Nuclear magnetic resonance spectra of both protons and N14 nuclei in nitrourethane and nitramide have been studied. Spectra are interpreted in terms of the structures R–NHNO2 and H2NNO2 for nitrourethane and nitramide, respectively. Protons have been established as all being of amino type.

The proton magnetic resonance spectra of conjugated aromatic hydrocarbons

The proton resonance spectra of a number of alternant aromatic hydrocarbons are reported. With the exception of benzene and pyrene, two or more signals were obtained for each hydrocarbon. A probable assignment of the spectrum for each compound is given, and this was confirmed for anthracene and phenanthrene by deuteration. The spectrum of the non-alternant hydrocarbon azulene is also presented. The observed nuclear magnetic resonance spectra of the aromatic hydrocarbons cannot be interpreted on the basis of symmetry considerations or π -electron density, but are readily explained in terms of a simple model based on induced diamagnetic currents in the conjugated aromatic rings. The spectra calculated for each hydrocarbon on the basis of this model satisfactorily reproduce the main features of the observed spectra.