25th International Meeting on Organic Geochemistry IMOG 2011

P-284
Nitrogen compounds in organic matter of rocks from Upper
Jurassic deposits of Western Siberia
Svetlana Yanovskaya 1 , Tatyana Sagachenko 1 , Heinz Wilkes 2
1 Institute of Petroleum Chemistry SB RAS, Academichesky Avenue, 4, Tomsk, Russian Federation,
2 Deutsches GeoForschungsZentrum, Potsdam, Germany
Distribution and compositions of nitrogen
compounds (NC) in organic matter (OM) of rocks from
Upper Jurassic deposits of West Siberia
(Bazhenovskaya suite) have been studied.
Bitumens were extracted using a methanolchloroform
mixture (7 : 93). The studied samples
differed with respect to the conditions of the initial OM
deposition (Pr/Ph=0.92–2.46) and the level of thermal
maturity (lower, moderate and higher).
To isolate NC we used a 25 % solution of sulfuric
acid in a 80 % solution of acetic acid. Based on nonaqueous
potentiometric titration and IR spectroscopy
the extracted NC in OM of rocks represent a mixture
of strong and weak bases. Depositional conditions
and the degree of OM thermal maturity had practically
no effect on total NC yield, the ratio of strongly and
weakly basic components and quantitative
compositions of the extracted compounds.
To obtain detailed information about NC
compositions the concentrates were divided into
fractions of strong and weak bases using a liquidadsorption
chromatography method.
Based on mass spectrometric data strong bases
of all samples under study are represented by alkyl-
and naphtheno-derivatives of quinoline, benzo- and
dibenzoquinoline, azapyrene, benzothiazole, and
thiopheno- and benzothiophenoquinoline. Weak
bases are represented by alkyl- and naphthenoderivatives
of cyclic amides of pyridine type and their
hydrated analogues – lactames. Alkyl- and
naphtheno-substituted quinoline-, benzoquinoline-
and dibenzoquinolinecarboxylic acids occur among
the bases of both types. Weak bases predominate
among the identified compounds.
Using a gas chromatography-mass spectrometry
it was determined that in all OM samples
alkylquinolines are represented by С4–С7 homologues
(m/z 185–227), alkylbenzoquinolines by С1–С5
homologues (m/z 193–249) and
mononaphthenobenzoquinolines by the first member
of the series and by С1–С2 homologues (m/z 233–
261). Based on the fragmentation patterns and
comparison with the published data we identified 2-
and 8-ethyldimethyl-, 2,4-dimethyl-8-isopropyl-, 2ethyltrimethyl-,
ethyltetramethyl-, 2,3,4-trimethyl-8-
isopropyl- and 8-isopropyltetramethylquinolines within
the alkylquinolines.
Among the С1–С3-alkylbenzoquinolines we
detected structures containing methyl substituents
only. Identified were 2-methyl-, 2,4- and 2,3-dimethyl-
and 2,4,6-trimethylbenzo(h)quinolines. It follows from
the analysis of mass spectra representing С4benzoquinolines
that they are composed of both fully
methylated structures and structures containing an
ethyl substituent in the position remote from a
nitrogen atom. Structural details and positions of the
substituents for С5-benzoquinolines have not been
determined.
Alkyl substituted mononaphthenobenzoquinolines
probably contain methyl substituents only.
Besides, we found the presence of С3–С4azapyrenes
(m/z 245–259), С1–С2-dibenzoquinolines
(m/z 243–257), С2–С4-thiophenoquinolines (m/z 213–
241) and С2–С3-benzothiophenoquinolines (m/z 263–
277) as constituents of the strong bases. The
substituents in azapyrenes are represented by methyl
or ethyl groups, while they are methyl groups only in
dibenzoquinolines and thiophenoquinolines. The
structures of substituents for
alkylbenzothiophenoquinolines have not been
determined.
It was shown that an oxidizing depositional
environment of the OM and its thermal transformation
result in an increased portion of polycyclic and
alkylated structures as well as thermodynamically
stable isomers within the strong nitrogen bases.
Using the data of mass spectral libraries NIST 21
and 107 it was determined that weak nitrogen bases
in the OM may have the structure of 2-hydroxy-3methyl-
(m/z 159) and 2-hydroxy-3,4dimethylquinolines
(m/z 173), 9(10H)-acridinone
and/or 6-hydroxyphenanthridinine (m/z 195) and
methylacridinone, in which a methyl group is loctaed
at positions 1, 2, 4 and 10 (m/z 209).
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