Kikuko Hayamizu

The analysis of the proton magnetic resonance spectra of monosubstituted benzenes: Part I. Additivity rule for the ring proton coupling constants

Abstract A complete analysis of the high resolution proton magnetic resonance spectraof monosubstituted benzenes has been performed as an AA′BB′C spin system, and the chemical shifts as well as the coupling constants are determined for 20 kinds of the compounds with great accuracy. The magnitude of each coupling constant is plotted against the electronegativity of the substituents, and empirical relations between the coupling constant and the electronegativity are given. An additivity rule for the coupling constants in the ring protons is presented, which permits an estimate of the ortho- and the meta -coupling constants in the disubstituted benzenes by making use of the ones in the monosubstituted derivatives.

The analysis of the proton magnetic resonance spectra of monosubstituted benzenes: The ring proton chemical shifts at infinite dilution

Abstract Proton magnetic resonance spectra of 22 kinds of typical monosubstituted benzenes have been completely analyzed as an AA′BB′C spin system, and the precise values of chemical shifts of ring protons are determined at infinite dilution in carbon tetrachloride. The dilution curves for the chemical shifts of each ring proton are obtained. A comparison is made between the chemical shifts of the monosubstituted benzenes and the substituent constants obtained from the chemical shifts of polysubstituted benzenes by application of the additivity rule.

The analysis of the proton magnetic resonance spectra of monosubstituted benzenes: Alkyl benzenes and an empirical interpretation of the ring proton chemical shiffts

Abstract The PMR spectra of alkyl benzenes, i.e., toluene and t -butyl benzene, were analyzed to determine the precise values of chemical shifts at infinite dilution in CCl 4 and spin-spin coupling constants between the ring protons. Using the chemical shifts hitherto obtained for typical monosubstituted benzenes at infinite dilution in CCl 4 , the linear relations of each ring proton chemical shifts are made between Tafts σ I and σ R constants. Although there are a few exceptions, the main changes of the ring proton chemical shifts due to the substituent may be interpreted by the two common factors.

On the determination of the chemical shift anisotropy for protons by liquid crystalline phases

Abstract The chemical shift anisotropy for protons of partially oriented molecules was studied, using p,p′-di-n-hexyloxyazoxybenzene (HAB) and a lyotropic mesophase (D 20 C 10 H 21 SO 4 NaC 10 H 21 OHNa 2 SO 4 system) as liquid crystalline phases. The anisotropic chemical shifts obtained in the lyotropic mesophase were compared with those obtained in the HAB solution. They have nearly the same values, although the two liquid crystalline phases used are quite different. A brief discussion is made of the reference substances. The results obtained in this work are consistent with the orientation of the long axis of the lyotropic mesophase perpendicular to the applied magnetic field.

Anisotropic proton chemical shieldings of methyl halides obtained from partially oriented molecules in a lyotropic mesophase

The anisotropic chemical shieldings of protons of four methyl halides are determined by a gradient method which has been reported previously, using a lyotropic mesophase (D2OC10H21SO4NaC10H21OHNa2SO4). These values are compared with those obtained by the same method from the p,p′-di-n-hexyloxyazoxybenzene (HAB) nematic medium. It is found that such nematic liquid crystals as HAB containing benzene rings are not suitable for the determination of the proton chemical shift anisotropy for a molecule orienting weakly to the long axis of the liquid crystalline phase. The variation in the obtained anisotropic chemical shieldings of the methyl halides from F, Cl, Br to I shows a trend similar to that of the calculated values from the magnetic dipole approximation. It seems to be justified that the neighboring group or atom having the large atomic magnetic susceptibility within a molecule plays an important role on the anisotropic chemical shieldings of the protons in such a case as the methyl halides.

Studies on the nuclear magnetic resonance spectra of olefinic protons of conjugated fatty acid methyl esters

The NMR spectra of olefinic protons in the four representative conjugated fatty acid methyl esters, methylcis-9,trans-11-octadecadienoate, methyltrans-9,trans-11-octadecadienoate, methyl α eleostearate, and methyl β eleostearate, were studied. The chemical shift of each olefinic proton in these compounds was determined by considering their intramolecular environment. Coupling constants were also obtained as the results of spectral analysis.

The relative signs of the long range spin-spin coupling constants in formic acid esters

Abstract The relative signs of the long range coupling constants through the carboxyl group in formic acid esters have been determined by the double resonance technique. The coupling constant between the formyl proton and the α-protons to the carboxyl group across four bonds is negative and that between the formyl proton and the β-protons separated by five bonds is positive. The long range coupling constants of several formic acid esters are given.

Nuclear magnetic resonance spectra of five isomers of 1,2,3,4,5,6-hexachlorocyclohexane

Abstract NMR parameters are determined by the complete analysis of the spectra for five isomers of 1,2,3,4,5,6-hexachloro-cyclohexane (BHC). Interesting correlations are found between the spin coupling constants and the chlorine atom configuration, which are interpreted by the conformational dependence of the electronegative substituents with respect to the coupled protons, as well as the small changes in the dihedral angle due to ring distortion. Some elucidations are made about the magnetic anisotropy effect of CCl bonds on the proton chemical shifts, and it is suggested that all of the proton shifts in BHC isomers cannot be explained only by the anisotropy effect, even after the solvent effect is eliminated. Proton decoupled 13 C spectra of these compounds are also observed.

1H and 13C Fourier transform spectra of β-1,2,3,4,5,6-hexachlorocyclohexane

Abstract The 13C satellites in the proton spectrum as well as the undecoupled 13C resonance spectrum of β-1,2,3,4,5,6-hexachlorocyclohexane were observed by the Fourier transform sensitivity enhancement technique. Because of the presence of the large main signal, the satellites in the proton spectrum were obtained by the long-term averaging technique. From both spectra the coupling constants between equivalent protons as well as 13CH coupling constants were extracted by the analysis as an ABB′CC′DX spin system. A brief discussion is given of the 13CH coupling constants.