Proton Resonance Spectra Research Articles

Proton and fluorine resonance spectra of some complexes of PF 5 and AsF 5

Chemical shifts, spin coupling constants and relative rates of quadrupole relaxation were determined for some complexes as a function of relative Lewis acid and Lewis base strength. Exchange behavior with an excess of acid or base was also studied.

Protonenresonanz-spektroskopie ungesättigter ringsysteme—IX : Die partielle analyse einiger bullvalen-spektren—ein beitrag zum problem der inneren rotation bei vinylcyclopropanen

The proton resonance spectra of several bullvalenes have been analysed. The coupling constants obtained have been compared with those in 1,3,5-cycloheptatriene. Consequences regarding the torsional potential of the vinyl group rotation in vinylcyclopropane have been derived. The results are in accord with a trans/gauche equilibrium. Additional evidence supporting this view is discussed.

Proton resonance spectra of some nickel complexes in aqueous solution

Download options Please wait... Article information DOI https://doi.org/10.1039/TF9696500915 Article type Paper Download Citation Trans. Faraday Soc., 1969,65, 915-927 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Proton resonance spectra of some nickel complexes in aqueous solution L. Pratt and B. B. Smith, Trans. Faraday Soc., 1969, 65, 915 DOI: 10.1039/TF9696500915 To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Search articles by author L. Pratt B. B. Smith

Hochauflösungs‐Protonenresonanz‐Spektren von Nitroäthylen, 1‐Nitropropen‐(1) und 1‐Nitropropen‐(2)

AbstractThe proton resonance spectra of nitroethylene, 1‐nitropropene‐(1), and 1‐nitropropene‐(2) have been measured in solution with high resolving power at 60 and 100 MHz. A full set of chemical shift and coupling constants, obtained from analysis of the spectra in terms of ABC, ABX3 and ABCD2 systems, respectively, is given.

Some remarks on the proton resonance spectra of poly‐α‐methylstyrenes

Abstract : Three different assignments have been given on the methyl signals of poly-alpha-methylstyrene but no conclusive evidence has been presented on this problem. Some experiments were carried on to obtain further evidence on the spectrum of poly-alpha-methylstyrene.

Nuclear Magnetic Resonance of Compounds Related to DDT: Part II. Aromatic Protons

The nuclear magnetic resonance spectra of the aromatic protons of DDT and 31 of its analogs and derivatives have been analyzed. Chemical shifts of these molecules are functions of the electronegativities of the substituents on the ring, as well as those in the aliphatic portion, although substitution of the ring chlorine in DDT by either a nitro or a t-butyl group leads to anomalous values. Molecular orbital calculations show that the chemical shift of the proton ortho to the ring substituent depends upon the π electron density at the corresponding carbon, but the chemical shift of the proton meta to this substituent is independent of the π electron density at the corresponding carbon. The data also indicate that the two aromatic rings in DDT are independent of each other.

Carbon tetrachloride as solvent in proton magnetic resonance. Importance of size and charge effects of proximate substituents

A model (not a theory), based on steric and charge removal characteristics of the substituents, is used to rationalize the low-field shifts caused by carbon tetrachloride (compared to cyclohexane) in the proton resonance spectra of 22 polyhalosubstituted benzenes. The low-field shifts are as large as 0.16 p.p.m. and these are found for protons situated between two ortho fluorine substituents. Larger halogens present a steric hindrance to the approach of the polarizable C—Cl bonds of the solvent and lead to smaller shifts. The charge removed from the region of the C—H bonds by the substituents is estimated by means of a function of the bond dipole divided by the bond length. A shape effect, arising when two hydrogens are ortho to each other, also appears to be present if there are bulky distant groups.

Strongly hindered rotation in α,α,2,6-terrachlorotoluene. Stereospecific five-bond coupling. Hyperconjugative contributions to long-range sidechain-ring proton coupling constants

At −40 °C the C—H bond of the dichloromethyl group of α,α,2,6-tetrachlorotoluene lies in the plane of the ring. The proton resonance spectrum demonstrates a stereospecific five-bond coupling between the C—H proton and the ring proton in the meta position. The coupling to the para proton is essentially zero as expected from a hyperconjugative mechanism. The free energy of activation of rotation of the dichloromethyl group is about 15 kcal/mole at 25 °C.

Quadrupole collapse of spin multiplets in the nuclear magnetic resonance of protons bonded to10B

The collapse of multiplet structures in the nuclear magnetic resonance spectra of protons bonded to boron was investigated using various boron compounds enriched or not enriched with 10B. The extent of collapse increases with increasing field gradient at the boron nuclei in the order of lithium borohydride (sp 3), trimethylaminoborane (sp 3), and n-tri(methyl-d3)-borazine (sp 2) (effect of field gradient). The collapse is stronger for 10BH signals than for 11BH signals, because the quadrupole moment of 10B is greater than that of 11B (effect of the quadrupole moment). With increasing temperature, the collapse decreases because the correlation time of molecular motion decreases (effect of the correlation time of quadrupole perturbation). Various typical line contours for the 10BH septet (a well resolved and equally spaced septet having the highest outermost peaks and the lowest second outermost peaks, a group of poorly resolved seven lines having maxima at both ends of the septet, and a broad flat-topped a...

Direct detection of anion shifts in the hydroxyl proton resonance spectrum of methanol

Direct detection of anion shifts in the hydroxyl proton resonance spectrum of methanol

Thioxan and selenoxan complexes of metal halides

Complexes of various metal halides with thioxan and selenoxan have been prepared and characterised; compounds prepared included BF3,C4H8OS, BCl3,C4H8OS, AlCl3,C4H8OS, AlCl3,C4H8OSe, AlBr3,C4H8OS, SnX4,2C4H8OS and SnX4,2C4H8OSe (X = Cl and Br), TiCl4,2C4H8OSe, TiCl4,C4H8OSe, and NbCl5,C4H8OSe. Compounds of silicon (IV) and germanium (IV) halides, or tin(IV) iodide could not be obtained. Infrared and proton resonance spectra measurements have been made on these and analogous reported compounds to establish the mode of co-ordination. In all cases except BF3,C4H8OS (and possibly BCl3,C4H8OS) co-ordination is through sulphur or selenium rather than oxygen. The significance of the results in relation to current views on A and B (hard and soft) acceptors is discussed.

The proton resonance spectrum of methyl 4,6-O-benzylidene-3-deoxy-3-phenylazo-α- d-glucoside 2-acetate : Partial virtual coupling in a four-spin system

A detailed interpretation of the PMR spectrum of the title compound is presented. Parameters include coupling constants across four bonds. Partial virtual coupling in the system ABMX is discussed in relation to this compound. With spin decoupling, this permits unambiguous determination of the relative signs of geminal and ( trans) vicinal coupling.

Proton Magnetic Resonance of Dimethyl Phthalates

We have studied the high-resolution proton magnetic resonance spectra of the ring protons in dimethyl phthalate, dimethyl isophthalate, and dimethyl terephthalate. The proton chemical shifts were determined relative to benzene in a series of solvents of widely varying dielectric constant, with both species at infinite dilution. This effectively removes the solvent van der Waals contribution to the observed shifts, and the remaining shifts are in accord with Buckingham's theory of dielectric reaction fields. Extrapolation to a medium of unit dielectric constant was performed in order to obtain chemical shifts typical of isolated molecules. These values were then approximately corrected for intramolecular electric and magnetic fields. For the two nearly planar molecules, the corrected values were correlated with pi-electronic charge densities obtained by Hückel molecular-orbital calculations. The failure of this correlation in the case of dimethyl phthalate can be attributed to the large deviations from planarity due to extreme steric hindrance.

Solvent effects on the proton spectra of some halopropenes. The preparation and proton resonance spectra of the 1-iodopropenes

The preparation and proton resonance spectra of the 1-iodopropenes are reported and solvent effects on the proton spectra of the chloro-, bromo-, and iodo-compounds are measured. The proton coupling constants are discussed in terms of old and new electronegativity correlations. The olefinic cis and trans proton shifts can be attributed mainly to a paramagnetic contribution from the substituent, whereas the gem olefinic proton shifts depend in addition on the electron-withdrawing power of the substituent. The methyl proton shifts in the 1-substituted compound show little dependence on the substituent and this is discussed in relation to the barrier heights to methyl rotation. The solvent shifts in benzene cannot be completely reconciled with a dipole – induced dipole model. They increase with the size of the substituent and are largest for protons farthest from the substituent. The solvent shifts in acetone can be explained as due to weak hydrogen bonding and reaction field effects. The shifts of protons gem to the substituent arise mainly from hydrogen bonding, whereas the shifts of protons cis or trans have significant contributions from both effects. The reaction field effects can also account for the methyl shifts in acetone.

Proton Resonance Spectra of Some Gas Hydrates

Proton resonance spectra have been obtained for a variety of clathrate hydrates as a function of temperature from near the decomposition point to about −70°C. It is possible to calculate the Arrhenius activation energy (∼8 kcal mole−1) for motional narrowing of the linewidths of the host molecules and this is attributed to the combined effects of rotation and diffusion in the solid. By selective deuteration linewidths are found for proton-containing guest molecules. The guest molecules undergo rapid rotation in the solid.

Proton-resonance spectra of selected mono-, di-, and trisubstituted silanes

Proton-resonance spectra of selected mono-, di-, and trisubstituted silanes

Nuclear magnetic resonance spectra of meta-difluorobenzene

Proton and fluorine resonance spectra of meta-difluorobenzene have been obtained under high resolution using a Varian spectrometer operating at 100 Mc/s and 94.1 Mc/s respectively. These have been analysed by treating the molecule as a six-spin system of the type AB 2 MX 2 with C 2v symmetry. The secular equation is solved using IBM 1620 and 7044 computers. The chemical shifts and coupling constants are reported.

13C splittings of proton and fluorine resonance spectra

13C satellites in proton and fluorine N.M.R. spectra have been used to obtain the coupling constants J 13c-h and J 13c-f for a number of ortho-, meta- and para-substituted fluorobenzenes. These coupling constants are found to depend on the substituent as well as the position of substitution. The 13C-H coupling constants, for a particular position, in general, increase with increase of the electron withdrawing power (expressed through Hammett σ-parameters) of the substituents. For a particular substituent, the values of 13C-H coupling constants increase with decrease of σ values and are found to change with the position of the substitution in the order meta < ortho < para. Such regularities are not found for 13C-F coupling constants.

Organosilicon compounds. Part II. The methyl proton resonance spectra of methylphenyldisiloxanes

The methyl proton shifts of the methylphenyldisiloxanes Me3SiOSiMe3 to Ph3SiOSiMePh2 have been determined and differences in shifts interpreted as arising from magnetic anisotropy rather than inductive mechanisms.

N.m.r. spectra of phosphine, arsine and stibine

A quantitative study is reported of the variation of proton chemical shift of PH3 and AsH3 and P—H coupling constant in PH3 with changes in concentration, temperature and solvent. The half-width of the proton resonance spectrum of AsH3 varies between 3 and 10 c/sec; this is consistent with incompletely effective electric quadrupole relaxation of the 75 As nucleus. The proton spectra of SbH3 and SeH2 are reported.