Oriented PMR spectra of acetone and DMSO and molecular orbital studies of 4JHH

Gopinathan, M. S. ; Narasimhan, P. T. (1972) Oriented PMR spectra of acetone and DMSO and molecular orbital studies of 4JHH Journal of Magnetic Resonance (1969), 6 (2). pp. 147-158. ISSN 0022-2364

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Related URL: http://dx.doi.org/10.1016/0022-2364(72)90122-9


The 100 MHz proton magnetic resonance spectra of acetone and dimethyl sulfoxide (DMSO) oriented in the nematic phase of 4,4'-di-n-hexyloxyazoxybenzene have been recorded. The spectra have been analyzed as A3 A3' spin systems. The four-bond indirect spin couplings between the methyl group protons are found to be 0.55 and 0.40 Hz for acetone and DMSO, respectively, in good agreement with the results obtained from 13C satellite studies. The signs and magnitudes of the orientation parameters for acetone have been obtained. The long-range four-bond proton couplings in acetone, isobutene and propane have been studied theoretically employing the finite perturbation SCF-MO method using CNDO/2 and INDO wavefunctions and the Pople-Santry method with extended Huckel theory (EHT) wavefunctions. The finite perturbation theory predicts the conformational dependence of these couplings satisfactorily whereas the Pople-Santry method is much less superior in this respect. The geminal proton couplings are found to be sensitive to the Slater orbital exponents used while the long-range four-bond couplings are not.

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