First Experimental Evidence for Buckybowls in Nature: Field Desorption and Atmospheric Pressure PhotoIonization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry of the Aromatic Fraction of Crude Oil

Ryan P. Rodgers², Jeremiah M. Purcell1^1,2, Tanner M. Schaub² and Alan G. Marshall²

^1.  Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306.

^2. Ion Cyclotron Resonance Program, National High Magnetic Field Laboratory, Florida State University, 1800 E Paul Dirac Drive, Tallahassee, Florida 32310-4005.

The recent application of Fourier Transform Ion Cyclotron Resonance Mass Spectrometry to petroleum characterization and petroleum geochemistry has exposed the immense chemical complexity of crude oil.  Atmospheric Pressure PhotoIonization (APPI) and Field Desorption (FD) provide ionization of hydrocarbons as well as nonpolar and polar N, S, and O containing compounds in crude oil.  Coupled to an FT-ICR mass spectrometer, both ionization techniques allow for the resolution and determination of unique elemental composition for each of thousands of species present in crude oil.

Here, we report FD and APPI FT-ICR MS analysis of the aromatic species isolated by SARA fractionation from an Arabian medium crude oil.  Hydrocarbon series (observable only by FD and APPI) showed double bond equivalence (DBE) values between 1 and 20 indicating the presence of both alkenes and multi-ring aromatics.  Surprisingly, we found hydrocarbon series at extremely high DBE (23-46) and extremely low H/C ratios (0.2 - 0.5).  The elemental compositions of more than a dozen such species exactly match those of the simplest "buckybowls" (highly condensed aromatic structures in which each five-membered rings is bordered by six-membered rings), beginning with underivatized corannulene (C₂₀H₁₀) and extending to larger bowls with more than 40 carbons and specific degree of alkylation.  To our knowledge, these results represent the first and most direct evidence for buckybowls in nature.  This work was supported by the NSF National High Field FT-ICR Facility (CHE-99-09502), Florida State University, and the National High Magnetic Field Laboratory in Tallahassee, FL