The 13C n.m.r. data of a variety of substituted adamantanes, diamantanes, and triamantanes are presented. The cc-substituted chemical shifts (SCS) can be described by gauche XC interactions, the magnitudes of which decrease in the sequence BrC > HC > OC 2 CC. Similarly, gauche interactions of the types HX and CX contribute to the (3-SCS. but additionally the (3-SCS are increased, if the a-carbon atoms possess antiperplanar y'-carbon atoms. Steric interaction of the substituent with gauche y-carbon atoms seem to cause rather downfield rather than upfield shifts of the y-signals. The hyperconjugative interaction of parallel C,-Cb-and Cg-C,<-bond orbitals increase the y,,,ii-SCS of the hydroxy and, to a smaller extent, the bromine substituent.

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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.

Fluorolube provides advantages as the mulling agent, since it is transparent in the region 1400-4000 cm"1, where absorptions due to hydrogen bonding are observed.

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