Molecular Evolution of N-Containing Cyclic Compounds in the Parent Body of the Murchison Meteorite

Abstract

Primitive meteorites contain various classes of organic compounds. Because the molecular distribution in these meteorites is not fully clarified, we do not yet understand the comprehensive formation mechanism(s) of extraterrestrial organic compounds. In this study, diverse and abundant alkylated homologues of N-containing cyclic compounds were identified in the methanol extract of the Murchison meteorite by electrospray ionization using high-performance liquid chromatography/ultrahigh-resolution mass spectrometry. More than 600 positive ions were assigned to C n H m N+ and C n H m N2 +, in which saturated and unsaturated alkylated pyridines and alkylimidazoles are predominant. Both can be synthesized from aldehydes and ammonia through aldol condensation and imine formation under an alkaline environment. Further redox reactions could have proceeded to make these molecules evolve to various CHN compounds, including alkylpiperidines and pyridine carboxylic acids. This study indicates that aldol condensation and formose reaction with ammonia are an important mechanism for the molecular evolution of N-containing compounds in the asteroid.

High‐mass resolution molecular imaging of organic compounds on the surface of Murchison meteorite

“…, ; Naraoka et al. ), and C n H 2 n ‐1 N + and C n H 2 n NO + homologues detected by DESI/HRMS (Fig. ) showed an association with matrix grains.…”

“…Furthermore, the separation of alkylpyridines and alkylimidazoles can also be achieved in centimeter scale using a chromatographic column by HPLC (Naraoka et al. ). Therefore, a similar process was also suggested to occur in the Murray meteorite, leading to the separations of alkylimidazoles and alkylpyridines by a previous study of DESI/HRMS conducted by our research group (Naraoka and Hashiguchi ).…”

“…In a more recent study, more than 600 peaks due to the presence of alkylated homologues of N‐containing heterocyclic compounds, which are mainly comprised of alkylimidazole and alkylpyridine, were identified by HPLC coupled with HRMS using Orbitrap MS in an MeOH extract obtained from the Murchison meteorite (Yamashita and Naraoka ; Naraoka et al. ). These studies suggested that the CHN compounds may have been synthesized and evolved during in situ H 2 generation via the aqueous alteration of meteoritic anhydrous silicates.…”

In situ organic compound analysis on a meteorite surface by desorption electrospray ionization coupled with an Orbitrap mass spectrometer

“…Or the C n H 2n‐4 N + homologues are less abundant locally. The bulk concentrations of these N‐heterocycles were estimated to be a sub‐ppm to ppm level in the methanolic extract of Murchison using HPLC/HRMS . Even though the standard compounds were not available in this study, ppm levels of alkylated CHN compounds can be detected using a DESI‐Orbitrap mass spectrometer.…”

“…azarelene) has been observed in crude oils depending on the migration distance, probably caused by their adsorption on clay minerals and/or solubility in interstitial water . Even though the fractionation occurred in a sub‐km scale by the geochromatography, the separation of alkylpyridines and alkylimidazoles was also achieved in ~cm scale using a chromatographic column by HPLC . Therefore, asteroidal chromatography is a candidate for separation of alkylpyridines and alkylimidazoles associated with the mobility of an aqueous fluid in the parent body, and the sub‐mm scale influence of fluid activity may be consistent with the previous models of fluid movement .…”