Molecular Diamagnetic Anisotropy and the Proton Magnetic Resonance Spectra of Condensed Aromatic Hydrocarbons

1957 ◽  
Vol 27 (2) ◽  
pp. 605-606 ◽  
Author(s):  
Genjiro Hazato
Keyword(s):  
Magnetic Resonance ◽  
Aromatic Hydrocarbons ◽  
Proton Magnetic Resonance ◽  
Diamagnetic Anisotropy ◽  
Magnetic Resonance Spectra

Proton magnetic resonance spectra of vinylmetallic compounds. Part I. Tetravinyl and triphenylvinyl derivatives of Group IVB elements

1968 ◽  
Vol 46 (14) ◽  
pp. 2373-2384 ◽  
Author(s):  
Seán Cawley ◽  
Steven S. Danyluk
Keyword(s):  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Phenyl Group ◽  
Coupling Constants ◽  
Multiple Quantum ◽  
Low Field ◽  
Diamagnetic Anisotropy ◽  
Vinyl Group ◽  
Derivatives Of ◽  
Magnetic Resonance Spectra

A study has been made of the proton magnetic resonance spectra for all of the Group IVB derivatives of the series MVi4 and [Formula: see text]([Formula: see text] = phenyl group and Vi = vinyl group). The spectra were measured at 60 MHz as accurately as possible and the assignment of transitions was checked with a variety of supplemental aids including double irradiation, multiple quantum transitions, and medium effects Final, accurate spectral parameters were derived using both iterative and exact computational methods for solution of the three-spin problem Excellent agreement was obtained between the sets of parameters determined by the two methodsThe chemical shifts for both series of compounds display a number of characteristic trends of which the most notable is a displacement of the vinyl proton signals to low field with increasing atomic number of the M atom In each series the largest shift change is noted in going from the carbon to the silicon derivative These deshieldings have been attributed to the enhanced possibility of dπ–pπ interaction between the central M atom and the vinyl group in higher members of the series Marked changes are also the internal shifts of the vinyl protons down both series of compounds It is concluded that these changes are principally due to the effects of the M—C bond diamagnetic anisotropy The trends in internal shifts can be satisfactorily reproduced by the dipole approximation using Δχ values of 4, 6, 8, 12, and 18 × 10−6 cm3 mole−1 for the C, Si, Ge, Sn, and Pb–carbon bonds respectivelyThe signals for the vinyl protons of the [Formula: see text] series are all located to low field relative to the MVi4 series This deshielding is satisfactorily accounted for by the effects of the phenyl ring diamagnetic anisotropy in the former seriesA linear correlation is observed between the sums of the coupling constants and the electronegativities, Em, of the central M atom for both series of compounds However, the ΣJ values for the [Formula: see text] series are all slightly lower than the corresponding sums for the MVi4 series, indicating that the electronegativity of the phenyl group is somewhat larger than for the vinyl groupA significant solvent and concentration dependence is only noted for compounds belonging to the [Formula: see text] series For example, the trans proton of [Formula: see text] shifts up-field by 4 Hz while the cis proton is displaced down-field by 4 Hz as the concentration of [Formula: see text] is increased to 50 mole % in carbon tetrachloride These changes have been interpreted on the basis of a solute–solute interaction scheme of the type proposed previously for phenyl proton shifts.

The proton magnetic resonance spectra of conjugated aromatic hydrocarbons

1956 ◽  
Vol 236 (1207) ◽  
pp. 515-528 ◽  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Simple Model ◽  
Aromatic Hydrocarbons ◽  
Proton Magnetic Resonance ◽  
Aromatic Rings ◽  
Proton Resonance ◽  
Nuclear Magnetic Resonance Spectra ◽  
Alternant Hydrocarbon ◽  
Magnetic Resonance Spectra

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.

The preparation of 2-Fluoro-5-nitrobenzonitrile and the proton magnetic resonance spectra of some compounds containing the N-(2-Cyano-4-nitrophenyl) group

1967 ◽  
Vol 20 (8) ◽  
pp. 1663 ◽  
Author(s):  
JFK Wilshire
Keyword(s):  
Amino Acids ◽  
Magnetic Resonance ◽  
Nitro Group ◽  
Proton Magnetic Resonance ◽  
Cyano Group ◽  
Aromatic Nucleus ◽  
Heteroaromatic Compounds ◽  
Magnetic Resonance Spectra

2-Fluoro-5-nitrobenzonitrile, an analogue of 1-fluoro-2,4- dinitrobenzene, in which the 2-nitro group has been replaced by a cyano group, has been prepared and made to react with several amines, amino acids, and NH-heteroaromatic compounds. The proton magnetic resonance spectra of some of the resultant N-(2-cyano-4-nitrophenyl) derivatives were compared with the spectra of the corresponding N-(2,4- dinitrophenyl) derivatives and furnish further evidence that the ortho nitro group of the latter derivatives is rotated out of the plane of the aromatic nucleus.

Investigation and Identification of the Bromination Products of Dimethoxyamphetamines

1976 ◽  
Vol 59 (5) ◽  
pp. 1162-1169
Author(s):  
Keith Bailey ◽  
Denise R Gagné ◽  
Richard K Pike
Keyword(s):  
Magnetic Resonance ◽  
Qualitative Analysis ◽  
Thin Layer ◽  
Thin Layer Chromatography ◽  
Infrared Spectra ◽  
Proton Magnetic Resonance ◽  
Positive Identification ◽  
Aromatic Bromination ◽  
Layer Chromatography ◽  
Magnetic Resonance Spectra

Abstract The qualitative analysis of the aromatic bromination products of the 6 isomeric dimethoxyamphetamines and their hydrochloride or hydrobromide salts is described. Their ultraviolet, mass, and proton magnetic resonance spectra are not sufficiently different for distinction but infrared spectra allow a positive identification to be made and reference spectra are provided for the bromination products of 2,4-, 2,5-, 2,6-, 4,5-, and 3,5-dimethoxyamphetamines. The application of gas-liquid and thin layer chromatography for the analysis of these products is discussed. The bromination of 2,3-dimethoxyamphetamine consistently gave mixtures which could not be separated satisfactorily; spectra are included for completeness of the comparison of products.

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