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Proton and Deuteron Magnetic Resonance of Phenylsilane-d,, Phenylphosphine-d,, and Benzenethiol-d in Liquid Crystal Solutions B. M. Fung and E. Y. Wei Contribution No. 406 from the Department of Chemistry, Tufts University, Medford, Massachusetts 02155. Received September 9, 1969 Abstract: The proton and deuteron magnetic resonance studies of phenylsilane-d3, phenylphosphine-d2, and benzenethiol-d in liquid crystal solutions at room temperature are reported. The orientation factors were calculated from the dipole-dipole splittings in the proton nmr spectra. The deuterium quadrupole coupling constants were calculated from the nuclear quadrupole splittings in the deuterium nmr spectra and the orientation factors obtained from proton nmr. Assuming axial symmetry for the field gradient, the deuterium quadrupole coupling constants were calculated to be 91 + 2,115 =t2, and 146 i 3 kHz, respectively, for the three compounds. They are correlated to bond force constants and atom electronegativities. In addition, the C-P-D bond angle for phenylphosphine-dz and the H-P-H bond angle for phosphine in liquid crystal solutions were calculated from their proton nmr spectra. They are 96.4 i 1.0 and 95.3 l.Oo,respectively.
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he nuclear quadrupole coupling constant is a n important quantity related to chemical bonding and molecular structure. In particular, the quadrupole coupling constant for deuterium has many interesting properties. For exampIe, it bears a linear relation to the force constant in the hydrides of the second row elements. In hydrogen-bonded systems containing the 0-D . .O bond, the deuterium quadrupole coupling constant is directly related to the 0-D distance3-j ~ ' ~ and Hadzi3 have suggested and 0-0 d i ~ t a n c e ; Blinc that it is a more sensitive quantity than the 0-D stretching frequency in evaluating the strength of the hydrogen bond. In deuteriocarbons, the deuterium quadrupole coupling constant imreases regularly as the hybridization of carbon changes from sp3, sp2, to sp;' it decreases with the introduction of electron-withdrawing substituents.8-10 In ferroelectric materials, the structural changes during the phase transitions are directly related to the deuterium quadrupole coupling constant. 4 , l 2 The quadrupole coupling constants of deuterium are quite small (e2qQ/h < 400 kHz) and difficult to measure directly by the conventional quadrupole resonance technique. l 3 They can be obtained from molecular beam and microwave experiments but are usually limited to small molecules in the gaseous state. The majority of data for deuterium quadrupole coupling constants has been obtained from nuclear magnetic resonance. Although deuterium nmr in the liquid state does not always yield reliable values of quadrupole (1) C. H. Townes and B. P. Dailey, J . Chem. Phys., 17, 782 (1948). (2) S. Z. Merchant and B. M. Fung, ibid., 50, 2265 (1969). (3) R. Blinc and D. Hadzi, Nature, 212, 1307 (1966). ( 4 ) R. Blinc, Adcan. Magn. Resonance, 3, 141 (1968). ( 5 ) P. L. Olympia, Jr., and B. M. Fung, J . Chem. Phys., 51, 2976 (1969). (6) G. Soda and T. Chiba, ibid., 50,439 (1969). (7) P. L. Olympia, Jr., I . Y . Wei, and B. M. Fung, ibid., 51, 1610 (1969). (8) J. L. Ragle and I
