NEWS OF THE WEEK
SHUTTERSTOCK
CUT EMISSIONS FIRST, REPORTS CONCLUDE GEOENGINEERING: Technology to
alter Earth’s climate is not ready
T
CO2 from vehicles is a significant source of greenhouse gas emissions.
HE NATIONAL RESEARCH COUNCIL (NRC)
is underscoring the need to reduce emissions of carbon dioxide before exploring ways to modify Earth’s climate. Altering the climate, often called geoengineering, would require significant additional research and global coordination, NRC concludes in two reports released on Feb. 10. The first priority should be cutting greenhouse gas emissions, NRC says. Next, the possibilities for altering the climate are carbon dioxide removal (CDR) and solar radiation management (SRM), the reports say. Both of these possibilities are hypothetical. CDR involves several strategies. They include increasing the uptake of atmospheric CO2 by boosting photosynthesis through land management and ocean iron fertilization, burning of biomass for energy coupled with carbon capture and storage, and direct air capture of CO2. In contrast, SRM would involve injecting sulfur
BIG DATA MEETS SMALL CATALYSTS ORGANIC CHEMISTRY: Data-intensive
approach teases out mechanism
B
CRISTIANE STORCK SCHWALM
Graduate students Milo (left) and Neel videoconference to decipher a reaction mechanism.
Y COMBINING MODERN DATA analysis techniques with classical physical organic and computational chemistry, chemists have developed a way to pin down the mechanism by which a chiral anion catalyst generates certain enantiomers. The method could help chemists rationally design more effective catalysts. By figuring out a reaction’s mechanism—the precise way the reactants come together to form products—chemists can learn how to tweak that transformation to improve upon it, by boosting the yield, for example. But mechanisms can be complicated, particularly those of enantioselective catalysts in which myriad attractive and repulsive nonbonding forces are at work. To get a better handle on what was happening in their CEN.ACS.ORG
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dioxide or other gases into the atmosphere to reflect the sun’s rays into space and thus reduce solar warming. If more fully developed, CDR has the benefit of removing the causes of climate change and ocean acidification. In contrast, SRM would only offset the warming effects of greenhouse gases and not stem acidification from ocean uptake of atmospheric CO2, the reports say. Methods for cutting greenhouse gas emissions are far more developed than either possibility for intervening in the climate, the NRC reports emphasize. The NRC committee that wrote the reports urges policy-makers to first reduce emissions, next explore CDR, and only then move to examine the potential of SRM after significant research and monitoring. “The Committee considers it to be irrational and irresponsible to implement [SRM] without also pursuing emissions mitigation, carbon dioxide removal, or both.” Pat Mooney, executive director of the ETC Group, an environmental and human rights organization, says, “The overblown and risky promise of geoengineering is the only escape hatch” left to the fossil-fuel industry. And some NRC panelists are adamantly opposed to SRM. For instance, Raymond T. Pierrehumbert of the University of Chicago wrote in the online magazine Slate that the idea of “fixing the climate by hacking the Earth’s reflection of sunlight is wildly, utterly, howlingly barking mad.”—STEVEN GIBB
reaction flasks, University of California, Berkeley, chemists F. Dean Toste and Andrew J. Neel teamed up with University of Utah chemists Matthew S. Sigman and Anat Milo. Together, they took a data-intensive look at an intramolecular dehydrogenative C–N coupling reaction that’s catalyzed by chiral phosphoric acid derivatives (Science 2015, DOI: 10.1126/science.1261043). Neel performed dozens of permutations of the reaction, tweaking both catalyst and substrate, and then shared his data with Milo, who applied modern data analysis techniques to them. “What they came up with,” Sigman says, “was a model to describe what look like very interesting interactions between substituents on both the catalyst and the substrate.” On the basis of that information, the chemists designed new catalysts, ultimately predicting how they would behave. “You’ve got all sorts of stuff going on in this reaction, which makes it difficult to figure out with classic kinetics,” Toste says. “But here’s an approach where you take every bit of data you’ve got and you build a model based on physical parameters and combine that with classical physical organic chemistry. Then you’ve got something that’s really powerful that I think anybody could use.” Steven E. Wheeler, a computational chemistry expert at Texas A&M University, says, “Toste and Sigman have shown that a data-driven approach to mechanistic analyses can complement traditional tools of physical organic chemistry, providing a key step toward a future in which big data is used to design small catalysts.”—BETHANY HALFORD
FEBRUARY 16, 2015
