scholarly journals THE RELATIVE ACCEPTOR POWER OF BORON TRIHALIDES AND BORANE TOWARD TRIMETHYLAMINE BY PROTON N.M.R. MEASUREMENTS

1964 ◽  
Vol 42 (7) ◽  
pp. 1518-1523 ◽  
Author(s):  
J. M. Miller ◽  
M. Onyszchuk
Keyword(s):  
Linear Relationship ◽  
Chemical Shifts ◽  
Dipole Moments ◽  
Chloroform Solution ◽  
Heats Of Formation ◽  
Methyl Proton ◽  
Acceptor Activity ◽  
Proton Resonances ◽  
Proton Chemical Shifts

Proton n.m.r. spectra of trimethylamine adducts of the boron trihalides and borane have been measured in chloroform solution. Chemical shifts of methyl protons relative to tetramethylsilane decrease in the order: BBr3 > BCl3 > BH3 > BF3, suggesting that this is the order of acceptor activity toward trimethylamine. This is supported by the existence of a linear relationship between methyl proton chemical shifts and the heats of formation, dipole moments, or infrared vibrational shifts of boron trihalide and borane adducts. Splitting of methyl proton resonances into quartets have been observed for (CH3)3N•BCl3 and (CH3)3N•BBr3 but not for (CH3)3N•BF3 and (CH3)3N•BH3.

THE RELATIVE ACCEPTOR POWER OF BORON TRIHALIDES TOWARD ACETONITRILE BY PROTON NUCLEAR MAGNETIC RESONANCE MEASUREMENTS

1966 ◽  
Vol 44 (8) ◽  
pp. 899-902 ◽  
Author(s):  
J. M. Miller ◽  
M. Onyszchuk
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Dipole Moments ◽  
Proton Nuclear Magnetic Resonance ◽  
Methyl Proton ◽  
Linear Relationships ◽  
Acceptor Activity ◽  
Nuclear Magnetic Resonance Spectra ◽  
Nuclear Magnetic

Proton nuclear magnetic resonance spectra of BF3, BCl3, and BBr3 adducts of acetonitrile have been measured in nitrobenzene solution. Single peaks were observed in each case and chemical shifts relative to tetramethylsilane decreased in the order BBr3 > BCl3 > BF3, suggesting that this is the order of acceptor activity toward acetonitrile. Linear relationships exist between methyl proton chemical shifts of CH3CN•BX3 and the heats of formation, dipole moments, and infrared vibrational shifts of the same or related adducts.

Correlations of substituent effects on proton and fluorine chemical shifts with inverse ionization potentials

1967 ◽  
Vol 45 (24) ◽  
pp. 3143-3151 ◽  
Author(s):  
T. Schaefer ◽  
F. Hruska ◽  
H. M. Hutton
Keyword(s):  
Electric Fields ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Group Iv ◽  
The Other ◽  
Ionization Potentials ◽  
Time Dependent ◽  
Practical Application ◽  
Methyl Proton ◽  
Proton Chemical Shifts

The fluorine and proton chemical shifts in some geminally disubstituted vinylidene fluorides and ethylenes are discussed. For these compounds, at least, there are difficulties with an interpretation based on intramolecular time-dependent electric fields. On the other hand, the shifts correlate with the inverse ionization potentials of the substituents, indicating a paramagnetic effect arising from the second term in Ramsey's expression. It is suggested that the effect operates via the bonds and not across space. Methyl proton shifts in a series of substituted methyl compounds of group IV, V, and VI elements show similar correlations. A practical application of the correlation to spectral analysis problems is given.

A magnetic resonance study of metal-porphyrin/caffeine complexes

1973 ◽  
Vol 334 (1599) ◽  
pp. 493-504 ◽  
Keyword(s):  
Chemical Shifts ◽  
Magnetic Moments ◽  
Chloroform Solution ◽  
Zero Field ◽  
Magnetic Resonance Study ◽  
Metal Porphyrin ◽  
Paramagnetic Resonance ◽  
Metal Porphyrins ◽  
Proton Resonances ◽  
Electron Paramagnetic

The effects are described of MnIII, FeIII, CoII, NiII, CuII and AgII porphyrins on the chemical shifts and linewidths of the proton resonances of caffeine, and of caffeine on the electron paramagnetic resonance spectra of CoII, CuII and AgII porphyrins in chloroform solution. The largest n. m. r. shifts are produced by divalent ions with the largest g tensor anisotropy, and trivalent ions with the largest zero-field splittings; metal porphyrins with the largest effective magnetic moments produce the most broadening of the resonances. The n. m. r. and e. p. r. effects are interpreted as arising from molecular complex formation between caffeine and the metal porphyrins. An attempt is made to relate the observed dipolar n. m. r. shifts and broadenings for CoII porphyrin-caffeine to the structure of the complex in solution. Acceptable structures were of the plane-to-plane type, with the metal situated above N9 of the five membered ring.

scholarly journals Methyl Substitution Effects on the Proton Chemical Shifts in Benzene

1966 ◽  
Vol 21 (5) ◽  
pp. 609-615 ◽  
Author(s):  
G. S. Reddy
Keyword(s):  
Dipole Moment ◽  
Inverse Relationship ◽  
Chemical Shifts ◽  
Substitution Effects ◽  
Electron Densities ◽  
Methyl Proton ◽  
Methyl Substitution ◽  
Calculated Dipole Moment ◽  
Proton Chemical Shifts ◽  
Good Agreement

Methyl substitution effects on aromatic and methyl proton chemical shifts in several mono-, di-, and trimethyl benzenes are studied. A new method for obtaining the changes in the ring proton chemical shifts from those of methyl proton shifts at the corresponding positions is used. The extra π-electron densities in toluene are calculated using the already known relation between the π-electron densities and the proton shifts in aromatic systems. An inverse relationship is obtained between the ionization potentials and the total methyl effects on the chemical shifts in this series of compounds as one would expect. Dipole moment of toluene is calculated, and a reasonably good agreement is found between the experimentally observed and the calculated dipole moment.

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