Several organic chemists and astrophysicists have been involved in researching the origin of the benzene ring (C6H6), an effective, hexagonal molecule including a total of six carbon along with six hydrogen atoms bonded together. It’s been more than 50 years of research on this specific topic.
According to astrophysicists, the formation of polycyclic aromatic hydrocarbons, popularly known as PAHs includes the benzene ring as its fundamental building block. Polycyclic aromatic hydrocarbons are considered the most basic compound or material that is formed from the dying, carbon-filled stars explosions. Stars are the swirling piece of mass and matter through which it is considered responsible for shaping the earliest forms of carbon. Several researchers conclude that they may be the reason behind the beginning of life forms on Earth.
However, polycyclic aromatic hydrocarbons also have some negative points regarding the survival of life forms on the earth. Polycyclic aromatic hydrocarbons are also emitted from the inner-processing of gas-powered combustion engines and industrial processing for crude oil refineries. These emitted polycyclic aromatic hydrocarbons get mixed in the air forming harmful toxic air pollutants that damage human life, along with several other species as well as ecology.
Key to carbon-free cars? Look to the stars
It’s a very big question that strikes every researcher in this field that how the first benzene ring was formed from the explosion of stars in the universe. Another mystical question is that how the chemical reaction involved in the combustion engine could alter the formation of benzene rings so efficiently and how they combine with air to form a toxic air pollutant.
The first real-time measurement was demonstrated with the help of lab-based techniques that the unstable particles, known as free radicals react under some specific cosmic conditions to form primal benzene rings from elementary hydrogen and carbon atoms. The demonstration was done at Florida International University, the University of Hawaii at Manoa, and Lawrence Berkeley National Laboratory. The successful outcomes from the observations were published by the researchers in the journal “Science Advances”.
They concluded that this is the key to understanding the evolvement of the universe. Each and every material is made up of the growth of carbon compounds. This specific insight is also considered to be very helpful in designing cleaner combustion engines for the car manufacturing industry.
There is another kind of free radical known as propargyl radical, having chemical formula as C3H3. This type of free radical is considered extremely reactive because of its property for losing an electron. This has been implied for several decades for the formation of the soot. According to the researchers, these free radicals combine together to form the first aromatic ring, also known as benzene, chemically represented as C3H3. + C3H3.
In this research, researchers have demonstrated the first radical propargyl self-reaction under combustion and astrochemical conditions. Using a coin-sized chemical reactor and under very extreme temperature, also known as “hot nozzle”, was used by the researchers. A very high temperature and a high-pressure environment were created inside the combustion engine. The moon of the planet Saturn, known as Titan is considered of having very rich in hydrocarbon in its environment. These two different environments were simulated by the researchers. The observation of this experiment resulted in the formation of isomers molecules having the same chemical formula but the atomic structure was very different from those two propargyl radicals that lead to the formation of the benzene ring.
This “hot nozzle” system technique was implemented a decade ago by the author Musahid Ahmed, who was the senior staff scientist at Lawrence Berkeley National laboratory. He used the Advanced Light Source for performing the synchrotron experiments. The following experiment was conducted on vacuum ultraviolet spectroscopy for the detection of the isomers individually. The Advanced Light Source is considered as a kind of particle accelerator, also known as synchrotron. This synchrotron is capable of generating extremely bright beams of light that ranges from infrared to the X-rays. The researchers controlled this technique for arresting the self-reaction of the propargyl radicals.
This experiment unfolded within a microsecond of time just before the formation of polycyclic aromatic hydrocarbons and their subsequent soot. This extra-ordinary outcome of the experiment was supported by the predictions done by the author Ralf Kaiser, who was a professor of chemistry at the University of Hawaii (Manoa), and the simulation of quantum chemistry was formulated by the author Alexander Mebel, who was a professor of chemistry in the Florida International University.
Both of the researchers believed that this is the first milestone in achieving a very cleaner combustion engine that will be very helpful for the modern car manufacturing industries. According to various analyses done by the researchers, it is considered that it will take more than 25 years from now for replacing the entire fleet of gas automobiles with electric vehicles. The success of the invention of the cleaner combustion engine will be very helpful in cleaning our environment as there will be very less emission of carbon dioxide from these engines. This combustion engine will be efficiently equipped in airplanes as well as gas-powered hybrid electric vehicles. According to Musahid Ahmed, the obtained outcomes will be extended for developing other measures for the study of the growth of polycyclic aromatic hydrocarbons. This advancement in generating polycyclic aromatic hydrocarbons will also be implemented in several other DOE missions including the desalination of water and environmental science.
He also added that the research will also be extended up to catching a buckyball, C60. This C60 is considered the biggest mysterious clue that will unfold several hidden secrets behind the law of symmetry. According to Kaiser, their research will also be very helpful in plotting a carbon map of the whole Universe. This would be very beneficial for astronomers. He also added that this would surely unfold the secret behind the cosmic origins by finding the carbon framework of the DNA from the body.
Long Zhao et al, Gas-phase synthesis of benzene via the propargyl radical self-reaction, Science Advances (2021). DOI: 10.1126/sciadv.abf0360