Ethyl formate (C2H5OCHO) and n-propyl cyanide (C3H7CN) were both discovered for the first time in interstellar space, or the volume of space that consists of matter such as gas and dust but not occupied by stars and their planetary systems.
Ethyl formate, also known as ethyl methanoate, is an ester that is formed when ethanol reacts with formic acid. N-propyl cyanide is a type of alkyl cyanide. They are different types of molecules, but within their own classes of molecules, each is the most complex organic molecule so far detected in interstellar space.
According to the April 22, 2009 SpaceDaily.com article Two Highly Complex Organic Molecules Detected In Space, “The results will be presented [by the scientists] at the European Week of Astronomy and Space Science at the University of Hertfordshire on Tuesday 21st April.”
The scientists involved with the research are A. Belloche, K.M. Menten, C. Comito, and P. Schilke (all from the Max Planck Institute for Radio Astronomy, Bonn, Germany), R.T. Garrod (from Cornell University, Ithaca, New York, U.S.A.), and H.S.P. Mueller (from the University of Cologne, Germany).
They used the Institute for Radio Astronomy in the Millimeter Range (IRAM) 30-m Millimeter Radio Telescope, which is a 30-meter radio telescope that operates in the millimeter range of radio wavelengths. Specifically, its instruments operate at the values of 3, 2, 1, and 0.9 millimeters.The telescope is located in Sierra Nevada, Spain.
The researchers detected the emissions of these two molecules from Sagittarius B2 (Sgr B2), which is located in the general vicinity of the center of our Milky Way Galaxy.
Specifically, the two newly-discovered molecules were found within a hot, dense cloud of gas named the Large Molecule Heimat.
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The paper announcing their discovery is entitled “Increased complexity in interstellar chemistry: Detection and chemical modeling of ethyl formate and n-propyl cyanide in Sgr B2(N).” It was submitted in arXiv.org on February 26, 2009.
“We analyzed this spectral survey in the LTE [local thermodynamic equilibrium] approximation. We modeled the emission of all known molecules simultaneously, which allows us to search for less abundant, more complex molecules. We compared the derived column densities with the predictions of a coupled gas-phase and grain-surface chemical code.”
“We report the first detection in space of ethyl formate (C2H5OCHO) and n-propyl cyanide (C3H7CN) toward Sgr B2(N). The abundances of ethyl formate and n-propyl cyanide relative to H2 are estimated to be 3.6e-9 and 1.0e-9, respectively. Our chemical modeling suggests that the sequential, piecewise construction of ethyl and n-propyl cyanide from their constituent functional groups on the grain surfaces is their most likely formation route. Ethyl formate is primarily formed on the grains by adding CH3 to functional-group radicals derived from methyl formate, although ethanol may also be a precursor.“
It is difficult for these scientits to locate such complex molecules out in interstellar space because their spectral features are difficult to identify.
In fact, one of the authors, Arnaud Belloche, states, "The difficulty in searching for complex molecules is that the best astronomical sources contain so many different molecules that their "fingerprints" overlap, and are difficult to disentangle.” [ScienceDaily.com]
Holger Mueller, another author, added, "Larger molecules are even more difficult to identify because their "fingerprints" are barely visible: their radiation is distributed over many more lines that are much weaker.” [ScienceDaily.com]
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However, they also state that the more complicated the structure of molecules found in interstellar space, the more likely they are to form in sections using basic patterns involving more simple molecules, such as methanol.
The researchers state that, based on the fact that such complex molecules form in a standardized manner, even more complex molecules may be present in interstellar space.
They will continue their work to find even more complex molecules, including amino acids, which are essential for life as we know it here on Earth.
The new newly discovered molecules are similar in size and complexity to amino acids.
Their work suggests that the materials necessary for life could exist in space even before stars and planets first formed.
Dr. Garrod stated, "It's the only formation method that is remotely able to reproduce the abundances and ratios that we see between the different sizes of molecules.... It certainly raises the possibility that you have many of the building blocks for life in space before even a planet is formed, which increases the chances for life to form, at least in my view." [Discovery News: "Complex Molecules Found in Milky Way's 'Sweet Spot'"]
The Max Planck Society press release "Tracking down organic molecules" adds more information about the discovery of these complex molecules in outer space.