Aromatic aldehydes and ketones in the Posidonia Shale, Hils Syncline, Germany

The low-polarity NSO compound fraction of Posidonia Shale bitumens has previously been shown to contain fluoren-9-ones and benzofluoren-9-ones as the quantitatively most abundant compound class. The present study, based on detailed gas chromatography-mass spectrometry describes the distribution of naphthaldehydes, alkylnaphthylketones, benzaldehydes, alkylphenylketones, 1-indanones and 1-tetralones as additional types of aromatic carbonyl compounds in these samples. Benzene-derived carbonyl compounds are less abundant than the other identified compound classes. The observed distributions show some remarkable maturity related variations. Particularly, the ratios of α- and β-isomers of naphthalene-derived carbonyl compounds behave in a similar manner to the corresponding hydrocarbons, i.e. they show a relative increase of the β-isomers with increasing maturity. The 1-indanone/(1-indanone + 1-tetralone) ratio (ITR) is suggested as a new heterocompound based maturity parameter. The carbonyl compounds described may be derived either from inter- and/or intramolecular acylation and formylation reactions or from oxidation of benzylic methylene groups of alkylated aromatic hydrocarbons.