J.H. Goldstein

Nuclear magnetic resonance and 13CH satellite spectra of selenophene and several haloselenophenes

Abstract Proton magnetic resonance spectra and their corresponding 13 CH satellite spectra have been observed at 60 Mc/sec and analyzed for selenophene and a number of its mono- and disubstituted halogen derivatives. Estimates of anisotropy effects produced by the substituents have also been applied to the chemical shift values. All of the parameters obtained have been compared with the corresponding values in the analogous thiophenes and in furan.

A precise determination of the proton coupling parameters in benzene

Abstract The 13CH satellite spectrum of benzene has been observed at natural abundance, and an exact analysis of the ABB′CC′X system has been performed. The ortho, meta, and para HH couplings were found to have the values 7.54, 1.37, and 0.69 Hz, respectively, and the 13CH coupling was determined to be 158.34 Hz. In addition the differences in the long-range 12CH couplings were determined by analysis. A comparison of the HH coupling constants in benzene and biphenyl is included.

The nuclear magnetic resonance spectra of acridine and some of its derivatives

The nuclear magnetic resonance spectra of acridine and five of its derivatives have been obtained in d6-dimethyl sulfoxide solution and the spectra analyzed. When allowance is made for estimated diamagnetic anisotropy effects the chemical shifts generally follow expectations based on chemical and valence theoretical considerations. Small but unmistakable long-range couplings from H9 to H1 and H4 can be interpreted in terms of inter-ring delocalization effects. Concentration effects on the chemical shifts of acridine in d-chloroform have also been observed and considered from the standpoint of molecular interactions.

Proton magnetic resonance spectra of 4-pyrone, chromone and xanthone

Abstract The proton magnetic resonance spectra of 4-pyrone, chromone, xanthone, and several substituted 4-pyrones have been obtained and analyzed at 60 mc/sec in CDCl 3 , solution. In addition the C 13 satellite spectra have been observed at natural abundance in 4-pyrone and utilized both in verifying the analysis of the proton spectra and in evaluating the C 13 H coupling constants. The results of the analyses have been employed in discussing the electronic structure and related properties of 4-pyrone and its benzologs.

The proton magnetic resonance spectra of the monohalobenzenes

Abstract Theoretical analyses of the PMR spectra of chloro-, bromo-, and iodobenzene, with the aid of deuterium decoupled spectra of the para deutero derivatives of the chloro- and bromo- compounds, have provided a complete set of spectral parameters for these compounds. Some surprisingly simple correlations have been observed between the shifts and the couplings, and between each of these and other molecular parameters. In general these results do not appear to be explicable in terms of the existing theories of these parameters.

The proton magnetic resonance parameters and solvent effects for 2-methylbenzoxazole, -benzothiazole and -benzoselenazole

Abstract The proton magnetic resonance parameters have been obtained for 2-methylbenzoxazole, -benzothiazole, -benzoselenazole and various derivatives over the full range of concentration in cyclo hexane and acetone. The coupling constants were found to be nearly independent of heteroatom, with the chemical shifts being influenced by the heteroatom, yielding the order of mesomeric release of charge into the fused ring as O ⪢ S > Se. The chemical shifts were found to be very concentration- and solvent-dependent, indicating the presence of strong molecular interactions. Long-range inter-ring coupling parameters are also discussed.

Proton magnetic resonance and 13CH satellite spectra of 4-pyrone: analysis and assignments

Abstract The proton magnetic resonance and three 13 CH satellite spectra of 4-pyrone have been examined in an effort to resolve previous disagreements in the assignment of two coupling constants. Least-squares analyses of the spectra were carried out with the requirement that a single set of parameters should satisfactorily predict all four observed spectra simultaneously. The structure of the satellite spectra and their dependence on all parameters involved have been studied in detail. The results provide an unambiguous assignment of all the parameters.

The proton magnetic resonance spectra of tetravinylsilane and vinylphenylsilanes

Abstract Proton magnetic resonance spectra of tetravinylsilane and the three vinylphenylsilanes in dilute cyclohexane solution, at 40 Mc s , have been analyzed and the parameters have been compared with those obtained for some vinylmethylsilanes under similar conditions. Calculations were made of the effect of the phenyl-group anisotropy on the vinylic shifts assuming free rotation of the phenyl rings. The anisotropy effects appear to be negligible except at the α-position, in which case observed and calculated values are in fair agreement. The β-shift values are interpreted as indicating that d π - p π , bonding between vinyl and Si is not appreciably affected by the phenyl substituents. The approximately constant phenyl substituent effect at the α-position indicates that the phenyl groups might be freely rotating.

Proton distance ratios and order tensor elements for several halobenzenes obtained in a lyotropic potassium laurate mesophase

Proton distance ratios and elements of the order tensor are obtained from nuclear magnetic resonance spectra of chloro-, bromo-, and iodobenzene partially oriented in a potassium laurate lyotropic mesophase. Corrections for harmonic vibrations are applied and it is shown that even for proton distance ratios these corrections are significant. Furthermore, the effects of solvent on the ratios determined are comparable to the effect of the substituent. Particular attention to weighting of the dipolar coupling in the structural analysis is necessary if values are to be judged significant to 1 part in 104. The elements of the order tensor are discussed in terms of the orienting influence of the interface and alkyl chains of the mesophase surfactant.

An investigation of intramolecular hydrogen bonding in some malonic acids using NMR techniques

Abstract The NMR spectra of aqueous solutions of malonic, methyl malonic, and isopropyl malonic acids have been examined over a wide pH range and variations in chemical shifts, line widths, and coupling parameters have been observed. Significant differences in the behavior of the proton—proton coupling (H α H β ) in methyl and isopropyl acids have been interpreted in terms of steric interactions which affect the rotamer populations over which the coupling is averaged. The occurrence of a minimum in this coupling for the isopropyl acid is attributed to an internally H-bonded structure which is most stable in the singly ionized acid.