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Abstract

The 17O quadrupole-coupling tensor in a single crystal of benzophenone was completely determined using high-field NMR, with B0 of 8.4 T. The sample crystals were 50% 17O enriched; the carbon in the carbonyl position was 90% 13C. All possible transitions of the 17O nucleus were observed. The 17O quadrupole-coupling tensor (QCT) was determined from the and the quadrupole splittings. The quadrupolecoupling constant and asymmetry parameter are ezgQih = 10.808 MHz and η = 0.369. The principal axis system of the QCT conforms to the local C2v symmetry of the carbonyl group. The fine structure of the 17O transitions, caused by 17O13C coupling, allowed determination of the 17O13C coupling tensor. The resulting CO distance r = 1.213Å agrees well with the X-ray data. By taking into account the second-order quadrupole shifts the 17O chemical-shift tensor could be determined from the trasitions. The principal axis that corresponds to the largest paramagnetic shift is parallel to the CO bond. The largest diamagnetic shift is perpendicular to the-CO plane. These findings are in good agreement with a Hartree-Fock calculation on the related compound formaldehyde.