The 13C n.m.r. spectrum of triamantane (3) observed at 22.64 and 62.8 M H z is assigned using selective lH decoupling. Internal strain causing geometrical distortions at the quaternary carbon leads to a non-additive downfield shift of its signal.IN the course of our investigations on the chemical and spectroscopic properties of substituted and unsubstituted diamondoid hydrocarbons we have made a detailed l3C n.m.r. study of triamantane (3). Triamantane is a C1,H,, hydrocarbon composed of three fused adamantane subunits and has Czu symmetry. Thus the molecule shows eight different types of carbon sites.

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