Abstract
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.
| Original language | English |
|---|---|
| Pages (from-to) | 449-456 |
| Number of pages | 8 |
| Journal | ACS Earth and Space Chemistry |
| Volume | 5 |
| Issue number | 3 |
| DOIs | |
| State | Published - Mar 18 2021 |
Funding
Notice of Copyright: This manuscript has been authored by UT-Battelle, LLC under contract no. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a nonexclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ). Acknowledgments This work is funded by the National Science Foundation (NSF) (EAR 1753125, 1638752, and 1248553). A.B. acknowledges the Dean’s Teaching Postdoctoral Fellowship from the College of Arts and Sciences, Florida State University. A.B. and C.S. acknowledge the Undergraduate Research Opportunity Program, Florida State University. B.H. and R.B. were supported by resources at the Spallation Neutron Source and the High Flux Isotope Reactor, DOE Office of Science User Facilities operated by the Oak Ridge National Laboratory (ORNL). Authors acknowledge the computing resources from the High Performance Computing, Research Computing Center, Florida State University. This work is funded by the National Science Foundation (NSF) (EAR 1753125, 1638752, and 1248553). A.B. acknowledges the Dean’s Teaching Postdoctoral Fellowship from the College of Arts and Sciences Florida State University. A.B. and C.S. acknowledge the Undergraduate Research Opportunity Program, Florida State University. B.H. and R.B. were supported by resources at the Spallation Neutron Source and the High Flux Isotope Reactor, DOE Office of Science User Facilities operated by the Oak Ridge National Laboratory (ORNL). Authors acknowledge the computing resources from the High Performance Computing, Research Computing Center, Florida State University.
Keywords
- Raman spectroscopy
- carbonaceous chondritic meteorite
- diamond anvil cell
- high pressures
- octadecane