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Sachtler: catalyst relatively easy to make
washing with water. Sachtler noted the iron is homogeneously distributed throughout the zeolite cavities and is as sumed to exist as a binuclear oxo species. Catalysts prepared by the gas-phase method are insensitive to 20% water va por, which is well above the 5 to 10% water vapor automobiles tend to emit. Sachtler pointed out that a small de crease in activity is observed after 100 hours of reaction. But unlike other metalloaded zeolites, Fe/ZSM-5 is restored to its original activity by brief exposure to oxygen at high temperature. Another ad vantage of the new method is that its cat alysts exhibit a maximum in activity at only 350 °C. Mitch Jacoby
From the ACS meeting
of the promising performance, Sachtler noted, Hall's results could not be repro duced with ZSM-5 from different sourc es. Furthermore, Hall's tests were con ducted at 500 °C—much hotter than typ Responding to the needs of academic sci ical automobile exhaust temperatures. entists, Columbus, Ohio-based Chemical "Hall's work was an important break Abstracts Service (CAS) has developed through, but even he had problems re SciFinder Scholar, a new version of its producing his own results," Sachtler said. award-winning desktop research tool for The difficulty, he explained, likely arose industrial scientists. CAS Director Robert from differences in the processes ven J. Massie announced the new productdors use to manufacture zeolites. Two available in December—at the national vendors may offer zeolite products with meeting in Las Vegas. the same stmcture and the same silicon"I'm very impressed," says University to-aluminum ratio, but still their catalytic of Utah chemistry professor Peter J. properties are likely to be different. Stang. "This is going to be a truly first"By using a gas-phase process to load rate tool for academic researchers at a zeolites with iron," Sachtler announced, reasonable price." Stang is a member of "we now have a route that leads to all the American Chemical Society Joint the beauty of Hall's catalyst but is much Board-Council Committee on CAS, which easier to prepare and appears to work at serves as a conduit to and sounding board a lower temperature." for ACS members on matters concerning Sachtler and postdoctoral researcher the database publisher. Hai-Ying Chen came up with their repro To build SciFinder Scholar, Christine ducible iron-loading process, which M. McCue, CAS manager of STN prod yields highly effective catalysts regardless ucts, and Roger J. Schenck, CAS senior of zeolite vendor and history, by switch new product development specialist, ing from an aqueous ion-exchange meth met with academic customers last year od to a vapor-based technique. In fact, to assess the needs of university faculty Sachtler added, Fe/ZSM-5 with a 1-to-l and graduate students. iron-to-aluminum ratio can be prepared These university researchers, McCue from zeolites with different silicon-to-alu says, helped CAS tailor a useful, afford minum ratios. The high iron content is able program. SciFinder Scholar provides necessary for good catalytic activity. access to the entire CAS database (about To make the catalyst, iron trichloride 14 million entries and counting), has a vapor is reacted with the acidic form of predictable pricing scheme, point-andthe zeolite, H+/ZSM-5, Sachtler explained. click access to search features, and ac The iron compound permeates the porous cess tailored to the shared-use university zeolite, forming iron dichloride and hydro environment. Campuswide access will gen chloride gas. The gas is evolved and be available between 5 PM and 5 AM lo the remaining chlorine is removed by cal time on weekdays and all day Satur
SciFinder Scholar targets academic chemists
day by a specified number of users. The system will not be available on Sundays when it is shut down for maintenance. Further information about availability can be obtained by calling (800) 753-4227. "We left in the smarts," McCue says of the new program. Academic users can search by chemical substance or reac tion, research topic, author name, or by specific reference to a CAS number or patent number. But because of the shared-use environment of a university, she says, features found in the industrial version—such as user preferences for desktop settings and access to subscrip tion journals—were omitted. Three university customers were se lected to be testers for an initial version of the product. So far, McCue says, CAS staffers have been receiving accolades from users at the test sites and from peo ple, including graduate students, stop ping by the CAS booth at the meeting exposition. "They're amazed at how fast it is," she says, "and at the size of the da tabase. The whole spectrum of chemists at a university is finding the information they need." William Schulz
RNA catalyzes Diels-Alder reaction The range of reactions capable of being catalyzed by RNA or modified RNA has been extended for thefirsttime to carboncarbon bond formation in the Diels-Alder cycloaddition reaction. The achievement has potential implications for both combi natorial chemistry and the "RNA world" hypothesis of chemical evolution. In the past few years, researchers have identified catalytic RNAs (ribozymes) that accelerate phosphodiester bond formation and cleavage, ester and amide synthesis, bimolecular nucleophilic substitution, and porphyrin metallation. Now, senior scientist Theodore M. Tarasow, research associate Sandra L. Tarasow, and vice president for chemis try Bruce E. Eaton of NeXstar Pharma ceuticals, Boulder, Colo., have extended this repetoire to catalysis of one of the central reactions of organic synthesis, the Diels-Alder cycloaddition reaction [Nature, 389,54(1997)]. The researchers used in vitro selec tion, a technique in which a large num ber of oligonucleotides are screened re petitively to isolate those exhibiting a de sired type of activity. They constructed a SEPTEMBER 15, 1997 C&EN 9
