Solid state 13C NMR analysis of Brazilian cretaceous ambers

Journal of the Brazilian Chemical Society

Ricardo Pereira²  Rosane A. S. San Gil¹  Ismar S. Carvalho¹  Antonio Carlos S. Fernandes¹  Débora A. Azevedo² 

[1] ,Universidade Federal do Rio de Janeiro Instituto de Química Laboratório de Geoquímica Orgânica Molecular e AmbientalRio de Janeiro RJ ,Brazil

关键词: amber;    13C CPMAS;    solid state NMR;    botanical affinities;    Lower cretaceous;    Brazilian basins;   

DOI  :  10.1590/S0103-50532011000100012

来源: SciELO

【 摘 要 】

13C cross polarization with magic angle spinning nuclear magnetic resonance (13C CPMAS NMR) spectra have been obtained for the first time to three Cretaceous amber samples from South America. The samples were dated to Lower Cretaceous and collected in sediments from the Amazonas, Araripe and Recôncavo basins, Brazil. All samples have very similar spectra, consistent with a common palaeobotanical source. Some aspects of the spectra suggest a relationship between Brazilian ambers and Araucariaceae family, such as intense resonances at 38-39 ppm. All samples are constituted by polylabdane structure associated to Class Ib resins, constituted by polymers of labdanoid diterpenes. Finally, information concerning some structural changes during maturation, such as isomerization of Δ8(17) and Δ12(13) unsaturations, were obtained by 13C NMR analyses. The results concerning botanical affinities are in accordance with previous results obtained by gas chromatography-mass spectrometry (GC-MS).

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