NEWS OF THE W EEK
BENZENE STAND-INS
1,2-dihydro-1,2-azaborine with substituents at the boron and nitrogen atoms. They also made four reference heterocycles designed to be nonaromatic. They then CHEMICAL BONDING: Crystal structures obtained X-ray crystal structures of all five compounds. indicate that rings containing a Compared to the reference compounds, the purported boron-nitrogen bond are aromatic benzene surrogate showed clear signs of the electron delocalization that is emblematic of aromatic compounds, such as a more planar six-membered ring with more homogeneous bond lengths. ITH A SYSTEMATIC SERIES of X-ray crysThe work “is extremely rigorous and provides tal structures, chemist Shih-Yuan Liu and unambiguous evidence for the aromatic character of coworkers at the University of Oregon, Eu1,2-dihydro-1,2-azaborines,” says Francois gene, provide evidence that a family of sixP. Gabbai, a boron chemistry expert at Texas membered rings featuring a boronA&M University. nitrogen bond has a benzenelike N “This is a thorough and beautifully simple nature (J. Am. Chem. Soc. 2008, Ph study,” adds Warren E. Piers of the Univer130, 7250). The compounds, B N sity of Calgary, in Alberta, who has utilized 1,2-dihydro-1,2-azaborines, Ph the B–N bond’s increased ionic character feature bonding characteristics Ph = phenyl relative to an all-carbon bond to make polyand other properties that could cyclic materials. make them valuable substitutes for The results, Liu cautions, are just one piece of evibenzenes in biomedical and materials research. dence for aromaticity and should be taken together Benzene is the quintessential aromatic comwith studies conducted by other teams. pound, stabilized by virtue of delocalized elecNonetheless, the findings enrich scientists’ untrons freely moving about its circular array of atoms. Liu’s work indicates that 1,2-dihydro-1,2- derstanding of aromaticity, a key concept of organic chemistry, says Todd B. Marder of Durham University, azaborines, related to benzene through substituin England, who studies boron compounds. “This is the tion of one of the ring’s bonds with a B–N bond, kind of fundamental chemistry that will no doubt find its share that special stability. way into textbooks,” he says.—CARMEN DRAHL Liu and coworkers synthesized a derivative of
X-ray crystal structure of a 1,2-dihydro1,2-azaborine derivative. Carbon = gray nitrogen = blue boron = orange hydrogen = white
WORLD’S FASTEST COMPUTER DEBUTS BREAKTHROUGH: New machine achieves
sustained petaflop performance in tests
IBM’s lead engineer, Don Grice, inspects Roadrunner before it is shipped to Los Alamos National Lab.
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EXT MONTH, a convoy of 21 tractor-trailers will unload the world’s fastest computer at Los Alamos National Laboratory in New Mexico. Named “Roadrunner” for New Mexico’s state bird, the supercomputer was created through a collaboration between LANL and IBM, which built and tested the unit at its Poughkeepsie, N.Y., plant. Roadrunner, the Department of Energy announced June 9, is the first computer to achieve a petaflop or 1,000 trillion operations per second of sustained performance. “It’s a speed demon,” says Thomas P. D’Agostino, administrator of DOE’s National Nuclear Security Administration, adding that it is twice as fast as the next quickest supercomputer, which is located at Lawrence Livermore National Laboratory. Its primary purpose, he notes, is to certify the reliability of the IB M
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U.S. stockpile of nuclear warheads without conducting underground nuclear explosions. Along with speed, Roadrunner is efficient, using but half the electricity of other supercomputers. Its speed and efficiency are due to the computer’s microprocessors, says Dave Turek, vice president of IBM supercomputing. He calls Roadrunner a “souped-up version” of Sony’s PlayStation 3 because the advanced microprocessors’ design grew from a joint project among Sony, Toshiba, and IBM to develop a specialized microprocessor for that top-end video-game console. For the first six months of shakedown at LANL, officials say Roadrunner will explore unclassified research projects, such as complex calculations concerning climate change and the origin of the universe. Other calculations will involve studies of physical and chemical interactions at the submolecular level that could lead to an enhancement in cellulosic production of biofuels. After the shakedown, however, about 75% of its work will be on classified defense R&D, including antiterrorism and nuclear nonproliferation issues and nuclear weapons research. About 25% of its computing time will be left available for unclassified R&D, lab officials say. In all, Roadrunner has 18,000 microprocessors and 80 terabytes of memory housed in 288 refrigerator-sized racks, filling up 6,000 sq ft of floor space. Its connections require 57 miles of fiber optic cable. Despite its efficiency, it draws almost 4 MW of electricity.—JEFF JOHNSON
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