The Analysis and Interpretation of High Resolution Nuclear Magnetic Resonance Spectra

The high resolution nuclear magnetic resonance spectra of three ompounds containing three nonequivalent spin 1/2 nuclei (H ) have been observed at several magnetic field strengths. The compounds studied were styrene, 2,4-dichloroaniline and 2,5-dichloroaniline. The spectra, which depart considerably from first order behavior, have been analyzed and it was found that the sam.e set of parameters describe the spectra at all the magnetic fields used. Using these compounds, combination lines have been observed for the first time and it was demonstrated that these lines are not always of small intensity, as had been commonly supposed. It was shown that in styrene the spin-spin coupling constants have the same sign. Methods were developed which aid greatly in the analysis of spectra of systems of three spins, when these spectra show the results of intermediate coupling between the nuclei. A Using these methods it is possible, in favorable cases, to determine the relative signs of the coupling constants without a complete analysis. Two substituted ethanes, CHCIBrCBrF2 and CHCI CC1F were studied; the spectra were found to exhibit the effects Sof internal rotation. The temperature dependences of certain chemical shifts and spin-spin couplings were measured, and an attempt made to interpret them in terms of the simple theory of rotational averaging which has appeared in the literature. Thesis Supervisor: John S. Waugh Title: Assistant Professor of Chemistry