For almost half a century, astrophysicists and organic chemists have been hunting for the origin of C6H6the benzene ring – an elegant, hexagonal molecule consisting of 6 carbon atoms and 6 hydrogen atoms.
Astrophysicists say the benzene ring may be the basic building block of polycyclic aromatic hydrocarbons or PAHs, the most basic materials formed by the explosion of dying carbon-rich stars. The swirling mass of matter would eventually give shape to the earliest forms of carbon – precursors to molecules that some scientists say are associated with the synthesis of the earliest forms of life on earth.
Paradoxically, PAHs also have a dark side. The industrial processes behind crude oil refineries and the internal workings of gas-fired internal combustion engines can emit PAHs, which can snowball into toxic air pollutants such as soot.
Exactly how the first benzene ring formed by stars in the early universe – and how internal combustion engines trigger the chemical reaction that changes the benzene ring to soot particle pollutants – has long mystified scientists.
But now researchers at the Lawrence Berkeley National Laboratory (Berkeley Lab), University of Hawaii at Manoa and Florida International University have demonstrated the first real-time measurement using laboratory-based methods of unstable particles called free radicals that react under cosmic conditions, getting elementary carbon and hydrogen atoms to fuse together in primary benzene rings.
The researchers say their findings were recently published in the journal Scientific progress, is the key to understanding how the universe evolved with the growth of carbon compounds. This insight can also help the automotive industry produce cleaner internal combustion engines.
A type of free radical called propargyl radical (C3H3) is extremely reactive due to its tendency to lose an electron and has been implicated in soot formation for decades. Researchers believed that the recombination of two free propargyl radicals, C3H3+ + C3H3·, Gave rise to the first aromatic ring, benzene.
The current study is the first demonstration of the so-called “radical propargyl self-reaction” under astrochemical conditions and combustion conditions. Using a high-temperature coin-size chemical reactor called a “hot nozzle”, the researchers simulated the high-temperature high-pressure environment inside an internal combustion engine as well as the hydrocarbonaceous atmosphere of Saturn’s moon Titan and observed the formation of isomers – molecules with the same chemical formula but different atomic structures. two propargyl radicals leading up to the benzene ring.
The hot nozzle technique co-authored by Musahid Ahmed, a senior researcher in the Berkeley Labs Department of Chemical Sciences, adapted 10 years ago in Berkeley Labs Advanced Light Source (ALS) for synchrotron experiments, relies on vacuum ultraviolet (VUV) spectroscopy to detect individual isomers. ALS is a type of particle accelerator known as a synchrotron that generates extremely bright light rays that range from infrared through X-rays.
The researchers controlled the technique to stop the self-reaction of the propargyl radical – which unfolds within microseconds – just before major PAHs and subsequent soot form. The compelling results support predictions from experiments led by co-author Ralf Kaiser, professor of chemistry at the University of Hawaii in Manoa, and quantum chemistry simulations formulated by co-author Alexander Mebel, professor of chemistry at Florida International University.
They believe that the discovery one day could lead to cleaner internal combustion engines. Having more efficient gas engines, some analysts say, is still important because it could take another 25 years before we can replace the entire fleet of gas vehicles with electric vehicles (EVs). In addition, aircraft equipment and the gas-powered component of hybrid plug-in EVs with cleaner internal combustion engines can help reduce CO2 emissions that contribute to climate change.
Ahmed said he plans to expand the methods used to study PAH growth and investigate other systems relevant to the DOE mission, such as desalination of water and environmental science.
“We also want to catch a buckyball, C60, one of nature’s greatest clues to the secrets behind symmetry, ”said Ahmed.
Kaiser added that their research could help astronomers plot a carbon map of the universe and reset the cosmic origins behind DNA’s carbon frames.
Study reveals ‘radical’ wrinkle in the formation of complex carbon molecules in space
Long Zhao et al., Gas phase synthesis of benzene via the self-reaction of the propargyl radical, Scientific progress (2021). DOI: 10.1126 / sciadv.abf0360
Provided by Lawrence Berkeley National Laboratory
Citation: Key for carbon-free cars? Look at the stars (2021, June 9) retrieved June 9, 2021 from https://phys.org/news/2021-06-key-carbon-free-cars-stars.html
This document is subject to copyright. Except for any fair trade for the purpose of private investigation or research, no parts may be reproduced without written permission. The content is provided for informational purposes only.