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for 7 % of the signal. At this time the tube was opened and fractionated in the vacuum line. The white crystals that passed through -35°and stopped at -60°had an mp of 80°anda vapor pressure of 25 mm at 25°and 8 mm at 0°(estimated bp 120°). The mass spectrum showed strong peaks at m/e 356 and 358 corresponding to the expected isotopes of (CF3)2CBrI+, míe 229 and 231 corresponding to (CF3)2CBr+, and weaker peaks at 337 and 339 corresponding to C3F5BrI+. Infrared absorption in the gas phase is very strong at 1258 and 1222 cm-1 and strong at 926, 892, 822, 735, and 695 cm-1.

The proton-decoupled, carbon-13 magnetic resonance (cmr) data have been determined for all of the five possible perhydroanthracene structural isomers and for four of the six possible perhydrophenanthrene compounds. The former are of known configuration, but the latter are unidentified in the chemical literature prior to the present work. The data are initially assigned to specific carbon positions using a parameter set derived from the methyldecalins. The calculated spectra are then refined by least-squares, regression analysis. New chemical shift parameters associated with boat and skew pentane conformations are discussed.he first tetradecahydroanthracene (or perhydroanthracene, abbreviated for convenience to PHA) isomer was synthesized about the turn of the century.2-4 It was soon recognized that other geometric isomers were possible6 and as many as 20 were suggested.6 Fries and Schilling ultimately delineated the correct number as being five,7 the last of which was synthesized only in recent years.8 Many workers contributed to the synthesis and characterization of the several isomers.7•9-14 X-Ray16 and electron diffraction16•17 work

The 13C nuclear magnetic resonance spectra of four diastereomeric, acyclic isoprenoids [farnesane (C15), pristane (C19), phytane (C20), and squalane (C30)] have been obtained as a means for interpreting hydrocarbon mixtures common in some fossil fuels and biosynthesized organic compounds. Multiple resonance environments were detected for carbons influenced by two or three chiral centers. Samples of farnesane and squalane were found to exhibit random stereochemistry, whereas the phytane sample was demonstrated to be a mixture of two isomers, probably the 6(R), 10(S), 14(R,S) compound. The sample of pristane consisted of a single diastereomer and was probably obtained from a natural product. It is shown that general chemical shift assignments can be made in this class of molecules by considering the number of carbons located at positions one, two and three bonds distant, while assignment of closely spaced lines may be made on the basis of diastereomerically induced chemical shifts. Using these principles, the structural features of two fossil fuels were analysed.