ASTROCHEMISTRY
Organics found on Ceres Dawn spacecraft spots aliphatic hydrocarbons on dwarf planet Scientists have spotted aliphatic organic molecules across a large swath of the dwarf planet Ceres (Science 2017, DOI: 10.1126/ science.aaj2305). The compounds were likely produced on Ceres itself, suggesting that the rich chemistry needed to create life’s building blocks exists throughout the solar system. An international team led by Maria Cristina De Sanctis at the National Institute of Astrophysics in Rome, examined spectra taken by NASA’s Dawn spacecraft, which has been orbiting Ceres since 2015. Ceres lies in the asteroid belt between Mars and Jupiter. The team found organics in a 1,000-sqkm area near the crater Ernutet. Dawn’s spectrometer isn’t sensitive enough to identify individual molecules, but the spectra it captured suggest substances rich in aliphatic carbon, such as the mineral asphaltite and kerite, a rubberlike compound. Scientists have observed extraterrestrial organics on some solar system bodies, such as comet 67P/Churyumov-Gerasimenko,
The team hypothesizes that Ceres’s hydrothermal activity, combined with clay and ammonia-bearing hydrated minerals on the dwarf planet, produced the organics. In a perspective accompanying the report, Michael Küppers at the European
Saturn’s moon Titan, and other asteroids. The new data from Ceres add another source of organics to the growing solar system list. Sun Kwok, director of the Laboratory for Space Research at Hong Kong University, calls the work “exciting,” saying it confirms the widespread presence of complex organics in the solar system. De Sanctis and her team also present evidence that the organics may have been produced on Ceres, rather than delivered via cometary impacts, a popular theory for how Earth was seeded with prebiotic compounds. The distribution of the Researchers found Space Agency notes that as a organics across Ceres’s surface aliphatic organics dwarf planet, Ceres may still is broader than would be exnear the 50-kmharbor internal heat from its pected if they were generated wide Ernutet formation period and may even by an impact, the researchers crater on Ceres. contain a subsurface ocean. say. And the heat from such an “This opens the possibility that impact would likely have destroyed the primitive life could have developed on Ceorganics anyway. res itself,” he writes.—ELIZABETH WILSON
SYNTHESIS
New amination chemistry brought to light
CREDIT: NASA/JPL-CALTECH/UCLA/MPS/DLR/IDA (CRATER)
Photogenerated radical cations yield amines previously impossible to make
ions are highly reactive and will add to many olefin classes with extraordinarily fast rates, allowing us to achieve these Flashes of light help chemists at Princeton site, Markovnikov regiochemistry. What’s types of intermolecular hydroaminaUniversity and Bristol-Myers Squibb drive more, the new reaction can produce highly tions.” he says. the hydroaminations of olefins to produce substituted amines (such as in the example “Knowles came up with an elegant substituted amines. The light-powered shown) that are impossible to make any approach to what was really an unsolved reaction gives chemists another tool for other way. problem,” comments Kami L. Hull, an installing amines in drugs and expert in anti-Markovnikov Iridium catalyst, other biologically important hydrofunctionalization at thiol cocatalyst, light + molecules. the University of Illinois, UrN N H bana-Champaign. Previous H The new hydroamination is noteworthy for its intermoexamples of anti-Markovnikov lecular reactivity, its use of unactivated In the reaction, irradiation of a secondhydroaminations, she points out, either reolefin substrates, its toleration of several ary alkyl amine in the presence of an iridquired activated olefins or directing groups, different functional groups, and its regiium catalyst and a thiol cocatalyst yields or produced stoichiometric amounts of oselectivity for anti-Markovnikov amine an aminium radical cation intermediate. unwanted by-products. Furthermore, Hull products—wherein the new C–N bond This species is responsible for the reacadds, Knowles’s olefin substrates are so enforms on the less substituted carbon of the tion’s anti-Markovnikov regiochemistry ergetically stable that they wouldn’t react olefin (Science 2017, DOI: 10.1126/science. and highly substituted products, explains without his photocatalytic approach, which aal3010). Most other examples of hydroam- Robert Knowles, who led the research really expands what chemists can do with inations result in products with the oppoeffort. “These alkyl aminium radical catthis reaction.—BETHANY HALFORD FEBRUARY 20, 2017 | CEN.ACS.ORG | C&EN
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