EXPLORING THE POTENTIAL FORMATION OF ORGANIC SOLIDS IN CHONDRITES AND COMETS THROUGH POLYMERIZATION OF INTERSTELLAR FORMALDEHYDE
EXPLORING THE POTENTIAL FORMATION OF ORGANIC SOLIDS IN CHONDRITES AND COMETS THROUGH POLYMERIZATION OF INTERSTELLAR FORMALDEHYDE
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DOI：
10.1088/0004-637x/771/1/19
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发表时间：
2013-07-01
影响因子：
4.9
通讯作者：
Cody, George D.
中科院分区：
文献类型：
--
作者：
Kebukawa, Yoko;Kilcoyne, A. L. David;Cody, George D.
星际甲醛的聚合，首先通过甲醛反应，然后通过随后的缩合反应，为原始太阳系天体中可能存在的丰富且化学高度复杂的有机固体提供了合理的解释。为了更好地了解该反应，对合成温度与所得分子结构的关系进行了系统研究。此外，还研究了氨的存在对反应速率和产物分子结构的影响。使用固态 C-13 核磁共振、傅里叶变换红外和 X 射线吸收近边缘结构光谱，将合成的甲醛聚合物与从原始陨石中分离出的球粒状不溶性有机物 (IOM) 直接进行比较。甲醛聚合物的分子结构在官能团水平上与原始球粒状 IOM 表现出相当大的相似性。向溶液中添加氨可提高较低温度下的聚合反应速率，并导致氮大量掺入聚合物中。从形态上看，甲醛聚合物以亚微米到微米大小的球状颗粒和球状颗粒聚集体的形式存在，与球粒状 IOM 中常见的有机纳米球非常相似。这些光谱和形态数据支持这样的假设：球粒陨石中的 IOM 和彗星中的难熔有机碳可能是在太阳系历史早期，在存在液态水的情况下，通过星子吸积后星际甲醛的聚合形成的。
Polymerization of interstellar formaldehyde, first through the formose reaction and then through subsequent condensation reactions, provides a plausible explanation for how abundant and highly chemically complex organic solids may have come to exist in primitive solar system objects. In order to gain better insight on the reaction, a systematic study of the relationship of synthesis temperature with resultant molecular structure was performed. In addition, the effect of the presence of ammonia on the reaction rate and molecular structure of the product was studied. The synthesized formaldehyde polymer is directly compared to chondritic insoluble organic matter (IOM) isolated from primitive meteorites using solid-state C-13 nuclear magnetic resonance, Fourier transform infrared, and X-ray absorption near edge structure spectroscopy. The molecular structure of the formaldehyde polymer is shown to exhibit considerable similarity at the functional group level with primitive chondritic IOM. The addition of ammonia to the solution enhances the rate of polymerization reaction at lower temperatures and results in substantial incorporation of nitrogen into the polymer. Morphologically, the formaldehyde polymer exists as submicron to micron-sized spheroidal particles and spheroidal particle aggregates that bare considerable similarity to the organic nanoglobules commonly observed in chondritic IOM. These spectroscopic and morphological data support the hypothesis that IOM in chondrites and refractory organic carbon in comets may have formed through the polymerization of interstellar formaldehyde after planetesimal accretion, in the presence of liquid water, early in the history of the solar system.