The use of high-field carbon-13 NMR spectroscopy to characterize chiral centers in isopranes

✍ Scribed by Don K. Dalling; Ronald J. Pugmire; David M. Grant; William E. Hull

• Book ID: 102950060
• Publisher: John Wiley and Sons
• Year: 1986
• Tongue: English
• Weight: 858 KB
• Volume: 24
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1260240303

✦ Synopsis

The uC nuclear magnetic resonance spectra of four diastereomeric, acyclic isoprenoids [farnesane (CIS), pristane (C19), phytane (Cm), and squalane (C,)] 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 mixhue of two isomers, probably the 6(R), lO(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.