title: 13C NMR spectroscopy of the insoluble carbon of carbonaceous chondrites.
abstract: 13C NMR spectra have been obtained of the insoluble carbon residues resulting from HF-digestion of three carbonaceous chondrites, Orgueil (C1), Murchison (CM2), and Allende (CV3).  Spectra obtained using the cross polarization magic-angle spinning technique show two major features attributable respectively to carbon in aliphatic/olefinic structures.  The spectrum obtained from the Allende sample was weak, presumably as a consequence of its low hydrogen content.  Single pulse excitation spectra, which do not depend on 1H-13C polarization transfer for signal enhancement were also obtained.  These spectra, which may be more representative of the total carbon in the meteorite samples, indicate a greater content of carbon in aromatic/olefinic structures.  These results suggest that extensive polycyclic aromatic sheets are important structural features of the insoluble carbon of all three meteorites.  The Orgueil and Murchison materials contain additional hydrogenated aromatic/olefinic and aliphatic groups.
authors.affiliation: Department of Chemistry, Arizona State University, Tempe 85287, USA.
authors.forename: J R
authors.initials: JR
authors.lastname: Cronin
authors.forename: S
authors.initials: S
authors.lastname: Pizzarello
authors.forename: J S
authors.initials: JS
authors.lastname: Frye
mesh_terms: D055580:Astronomical Phenomena; D001256:Astronomy; D002244:Carbon / Q000032:analysis*; D002247:Carbon Isotopes; D006859:Hydrogen / Q000032:analysis; D009682:Magnetic Resonance Spectroscopy; D019110:Meteoroids; D011084:Polycyclic Aromatic Hydrocarbons / Q000032:analysis*; D013057:Spectrum Analysis
chemical_list: D002247:Carbon Isotopes; D011084:Polycyclic Aromatic Hydrocarbons; D002244:Carbon; D006859:Hydrogen