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Spectroscopic Investigation of the High-Pressure Behavior of Aliphatic Hydrocarbon: Implications for Planetary Processes
ACS Earth and Space Chemistry ( IF 2.9 ) Pub Date : 2021-02-10 , DOI: 10.1021/acsearthspacechem.0c00259
Abhisek Basu 1 , Mainak Mookherjee 1 , Christina Schiffert 1 , Bianca Haberl 2 , Reinhard Boehler 2
Affiliation  

Octadecane (C18H38) is an aliphatic hydrocarbon that is abundant in carbonaceous chondritic meteorites. It is debated whether these hydrocarbons found in the meteorite are pristine or are a result of subsequent modifications as these meteorites are delivered to the Earth. It is well-known that meteorites are often subjected to extreme pressures and temperatures upon entering the Earth’s atmosphere. To explore the behavior of octadecane at high pressures, that is, how its molecular structure responds to compression, we use a diamond anvil cell in conjunction with Raman spectroscopy. We find that at room temperatures, upon compression to ∼5 GPa, a linear-chain octadecane molecule transforms into a bent-chain configuration. Similar transitions from linear to a bent configuration in other hydrocarbons have been documented. We find a linear correlation between the transition pressure from linear to bent configuration, and the chain length of the alkane, that is, longer chain lengths, is likely to be less stable in the linear configuration under compression. These kinks in the bent-chain configuration are likely sites for the dissociation of the longer chain hydrocarbons to smaller hydrocarbons. The octadecane sample examined in this study did not undergo any additional transition to the highest pressure (∼18 GPa) explored in this study.

中文翻译:

脂肪烃的高压行为的光谱研究:对行星过程的影响

十八烷(C 18 H 38)是一种富含碳质球状陨石的脂族烃。争论在陨石中发现的这些碳氢化合物是原始的,还是由于这些陨石被运送到地球上而进行了后续修饰的结果。众所周知,陨石在进入地球大气层时通常会承受极高的压力和温度。为了研究十八烷在高压下的行为,即其分子结构如何响应压缩,我们将金刚石砧座细胞与拉曼光谱法结合使用。我们发现,在室温下,压缩至约5 GPa时,直链十八烷分子会转变为弯链构型。已经记录了在其他烃中类似的从线性构型到弯曲构型的转变。我们发现从线性构型到弯曲构型的转变压力与烷烃的链长(即较长的链长)之间的线性相关性可能在压缩状态下在线性构型中不太稳定。弯曲链构型中的这些扭结可能是长链烃解离为较小烃的位置。在本研究中检查的十八烷样品未经历任何其他转变,达到本研究中探索的最高压力(约18 GPa)。
更新日期:2021-03-18
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