14:00 〜 14:15
[PPS12-14] 太陽系小天体におけるホルムアルデヒドとアンモニアの化学
キーワード：隕石、小惑星、有機物
Formaldehyde and ammonia is ubiquitous in the universe. Comets contain up to 4% H2CO and up to 1.5% NH3 relative to H2O, and interstellar medium (ISM) contains up to 8% H2CO and up to 80% NH3 relative to H2O [1]. Cody et al. [2] proposed the formation scenario of insoluble organic matter (IOM) in chondritic meteorites, in the presence of liquid water starting with formaldehyde and glycolaldehyde that is the simplest sugar produced by two H2CO molecules. We have conducted further experimental studies and showed that the presence of ammonia enhanced the IOM like organic solid formation via formose reaction followed by carbonization [3]. These studies were focusing on the solid materials, and now we study the liquid phase of the products with various analytical methods including electrospray ionization mass spectrometry (ESI-MS), X-ray absorption near edge structure (XANES), infrared spectroscopy and amino acid analyses using high performance liquid chromatography (HPLC).
Each starting solution contained 1mL water with 2 mmol formaldehyde, 1 mmol glycolaldehyde, 0.4 mmol ammonia (equivalent to H2O : C : N = 100 : 7.2 : 0.72) with catalytic amount of Ca(OH)2, and was sealed in a glass tube, then isothermally heated at 90 degrees C up to 250 degrees C. XANES and FTIR analyses showed that aromatic or olefinic C=C bond abundance increased with temperature in the soluble fractions. This indicates that the insoluble residues precipitate as a result of increase in the hydrophobic moieties in the products as the reaction proceeds. This is consistent with the previous results that the amount of insoluble fractions (organic solids) increases with temperature [3]. Acid hydrolysis of the solutions produced various amino acids up to four carbons. Alanine abundance was larger than glycine, and may indicate high abundance of methyl (-CH3) or methylene (-CH2-) substitutions in the amino acid precursor molecules. ESI-MS results suggested that various carbohydrates (CHO molecules) and these with nitrogen containing substitutions. This is somewhat consistent with ultrahigh-resolution ESI-MS analysis of the Murchison meteorite extract that shows various CHO and CHNO molecules [4], although only formaldehyde and ammonia chemistry cannot explain all of the diverse molecules found in this meteorite.
References:
[1] Charnley, S. B. and Rodgers, S. D. (2008) Space Science Reviews, 138, 59-73.
[2] Cody, G. D., et al. (2011) Proceedings of the National Academy of Sciences of the United States of America, 108, 19171-19176.
[3] Kebukawa, Y., et al. (2013) The Astrophysical Journal, 771, 19.
[4] Schmitt-Kopplin, P., et al. (2010) Proceedings of the National Academy of Sciences of the United States of America, 107, 2763-2768.
Each starting solution contained 1mL water with 2 mmol formaldehyde, 1 mmol glycolaldehyde, 0.4 mmol ammonia (equivalent to H2O : C : N = 100 : 7.2 : 0.72) with catalytic amount of Ca(OH)2, and was sealed in a glass tube, then isothermally heated at 90 degrees C up to 250 degrees C. XANES and FTIR analyses showed that aromatic or olefinic C=C bond abundance increased with temperature in the soluble fractions. This indicates that the insoluble residues precipitate as a result of increase in the hydrophobic moieties in the products as the reaction proceeds. This is consistent with the previous results that the amount of insoluble fractions (organic solids) increases with temperature [3]. Acid hydrolysis of the solutions produced various amino acids up to four carbons. Alanine abundance was larger than glycine, and may indicate high abundance of methyl (-CH3) or methylene (-CH2-) substitutions in the amino acid precursor molecules. ESI-MS results suggested that various carbohydrates (CHO molecules) and these with nitrogen containing substitutions. This is somewhat consistent with ultrahigh-resolution ESI-MS analysis of the Murchison meteorite extract that shows various CHO and CHNO molecules [4], although only formaldehyde and ammonia chemistry cannot explain all of the diverse molecules found in this meteorite.
References:
[1] Charnley, S. B. and Rodgers, S. D. (2008) Space Science Reviews, 138, 59-73.
[2] Cody, G. D., et al. (2011) Proceedings of the National Academy of Sciences of the United States of America, 108, 19171-19176.
[3] Kebukawa, Y., et al. (2013) The Astrophysical Journal, 771, 19.
[4] Schmitt-Kopplin, P., et al. (2010) Proceedings of the National Academy of Sciences of the United States of America, 107, 2763-2768.