NEWS OF THE WEEK
CFC DESTROYING REACTION Convenient method uses sodium oxalate hemists at Yale University have discovered a convenient and inexpensive reaction that could be used to destroy supplies of chlorofluorocarbons (CFCs), chemicals that are being phased out because they destroy Earth's protective ozone layer. The method involves passing the CFC through a packed bed of powdered sodium oxalate, (COONa)2, at 270 to 290 °C The reaction products are sodium fluoride, sodium chloride, elemental carbon, and carbon dioxide. When heated to only 230 °C, the same reagent removes some of the fluorine atoms from cyclic perfluoroalkanes to yield perfluoroarenes. The researchers point out that this reaction is potentially important because perfluoroalkanes—which normally are highly unreactive—are much more readily available than are perfluoroarenes, which are valuable chemical intermediates. The work was carried out by Yale chemistry professor Robert H. Crabtree and graduate student Juan Burdeniuc [Science, 271, 340 (1996)]. A number of methods have been proposed to destroy stockpiles of CFCs when these chemicals—once widely used as refrigerants, heat-transfer media, and propellants—are totally replaced by more environmentally friendly compounds. These methods include incineration and reaction with
C
molten sodium, both of which have drawbacks. Incineration produces corrosive gases, and molten sodium is dangerous to handle. The sodium oxalate reaction is attractive for CFC destruction, the Yale researchers note, because it requires "only very simple hot-tube chemistry,, and uses an inexpensive, noncorrosive reagent. (Sodium oxalate is commercially available for less than $50 per kg.) Moreover, the solid products are all easily handled. Sodium fluoride, which is used as a commercial fluorinating agent, can be recycled. Because CFCs contain chlorine, the reaction produces a mixture of NaCl and NaF—but this outcome "is not that big of a problem," says one chemist. However, a possible drawback is that the reaction also produces C0 2 , which contributes to global warming through the greenhouse effect. But Crabtree isn't too concerned, he says, because his group already has found a better reaction for destroying CFCs that doesn't release C0 2 . The method also is useful for partial defluorination of perfluoroalkanes. But he cannot yet divulge any details. The Yale oxalate reaction is "a real advance" and has commercial potential, says R. Tom Baker, a chemist at DuPont's Experimental Station in Wilmington, Del. Baker has developed a metal-
Perfluoroalkane is partially defluorinated in two stages
Perfluorodecalin
Perfluorotetralin
Perfluoronaphthalene
Perfluorodecalin was reacted with sodium oxalate at 230 °C to give two aromatic products, with yields depending on exact reaction conditions. 6
JANUARY 22,1996 C&EN
Burdeniuc (left) and Crabtree show off the apparatus they devised to reflux fluonnated liquids through a heated bed packed with sodium oxalate. catalyzed process for replacing the chlorine in CFCs with hydrogen. Several companies have expressed interest in the oxalate reaction. However, says Crabtree, its commercial prospects will depend in part on engineering, economic, and even political issues, as well as competitive processes. "I just can't predict what's going to be the final story on this [discovery]." Crabtree and Baker note that no CFC destruction facilities are now operating. And as of Jan. 1, CFC production in industrialized countries was supposed to have stopped. People have been stockpiling CFC supplies in case they are needed. But if the transition to CFC replacements (such as hydrochlorofluorocarbons) continues to go well, Crabtree points out, CFC stockpiles will have to be destroyed, probably starting in three to five years. Burdeniuc and Crabtree's discovery
of sodium oxalate's utility in CFC destruction is an outgrowth of a project aimed at finding better ways to partially defluorinate cyclic perfluorocarbons (C&EN, Oct. 23, 1995, page 26). "We looked for a two-electron reducing agent, on the grounds that fluoroalkenes are stabler intermediates than are the radicals that would be formed in a one-electron reduction," they explain in Science. "We wanted to combine the reductant with a fluoride-abstracting component, such as a metal cation." Burdeniuc, whom Crabtree describes as "a really inventive guy," was the one who thought of trying sodium ox-
alate. "Nobody would have given him any money to study that because sodium oxalate is such a wimpy reagent," Crabtree remarks. No one would have thought it would react with perfluoroalkanes, among the most refractory of all compounds, he adds. But once the Yale chemists saw how well the oxalate reaction worked with perfluorocarbons, Crabtree suggested trying it with CFCs. A variety of defluorination reagents had been developed previously, but they typically are expensive, inconvenient to use, or difficult to stop at the partial-defluorination stage. In commer-
Dow-Eli Lilly venture buys stake in Mycogen DowElanco—an agricultural products company that is a joint venture between Dow Chemical and Eli Lilly—will pay $152 million in cash and turn over its seed business to acquire a 46% stake in Mycogen, a San Diego-based agricultural biotechnology company. DowElanco, based in Indianapolis, has about $2 billion in worldwide annual sales. Dow Chemical owns a 60% share and Eli Lilly owns 40%. To gain its stake in Mycogen, DowElanco will purchase 9.5 million shares currently owned by Lubrizol, which is Mycogen's largest shareholder. These shares include 3.4 million newly issued shares resulting from Lubrizol· s conversion of its 19.5% interest in Mycogen's seed business and its holding of $31.6 million worth of Mycogen preferred stock. As part of the deal, Mycogen will acquire DowElanco's United AgriSeeds
Mycogen at a glance Revenues: $113 million in fiscal 1995a Net loss: $15.9 million in fiscal 1995a Headquarters: San Diego Founded: December 1982 Employees: 770; acquisition will add 200 from DowElanco's United AgriSeeds business Major product areas: Genetically enhanced pest-resistant seeds for crops, biopesticides, and crop protection services a Fiscal year ending Aug. 31, 1995.
business. Mycogen will exchange about 4.5 million newly issued shares of its common stock for the seed business and about $26 million in cash from DowElanco. Combined sales for United AgriSeeds and Mycogen's existing seed business would have exceeded $100 million in 1995. Mycogen also will spend $8 million to reacquire certain rights in oil seed technology from Lubrizol. Lubrizol, no longer considering Mycogen a strategic fit with its other businesses, will be cashing out its entire investment in the company. The two companies have been allied since 1987, when Lubrizol signed R&D contracts with Mycogen and bought a 16% stake. In 1992, Mycogen took a majority share in Lubrizol's Agrigenetics seed division. Mycogen also has marketing and R&D alliances with the Ciba Seeds division of Ciba-Geigy, with Japanese companies Kubota Corp. and Japan Tobacco, and with U.S. seed producer Pioneer Hi-Bred. The Mycogen deal will be DowElanco's largest biotechnology alliance to date, says a company spokesman. The firm has taken small equity positions in U.K.-based AGC, and in Boulder, Colo.based RPI, as well as set up research agreements with universities. DowElanco's 1988 acquisition of United AgriSeeds gave the company in-house biotechnology research capabilities. "This alliance is a major step forward in biotechnology for DowElanco," says President and Chief Executive Officer John Hagaman. "We believe that biotechnology will play a very major role in the development of future products for agriculture and offers multiple areas of substantial opportunity." For example,
cial operations, iron or nickel is often used at 450 to 500 °C, but this produces metal fluoride that requires disposal. One of the advantages of the oxalate reaction is that it allows partial defluorination of a saturated ring system. For example, the Yale researchers can convert perfluorodecalin into two different aromatic products: perfluorotetralin, which results from loss of six fluorine atoms, and perfluoronaphthalene, which results from loss of 10 fluorines. The reaction conditions can be tailored to produce more perfluorotetralin than perfluoronaphthalene. Ron Dagani last August Mycogen received Environmental Protection Agency approval to begin marketing seed corn genetically engineered for resistance to the European corn borer, a major corn pest. When the transaction is completed, DowElanco will own about 14 million of Mycogen's 30.4 million outstanding shares and will have the right to acquire additional shares. The deal is similar to one struck last October between Monsanto and Calgene, a Davis, Calif.-based agricultural biotechnology company. Ann Thayer
New technique boosts diamondfilmdeposition A small, privately held company in Dearborn, Mich., has achieved a major breakthrough in deposition of diamond films on a wide variety of materials. QQC Inc.—an affiliate of machine tool maker Turchan Inc.—has developed a technique that inexpensively deposits diamond films of varying thicknesses in a process analogous to spraying paint on a surface. Metallurgist Pravin Mistry, QQC president, came upon the technique two years ago. The coating is done at room temperature—without the vacuum, 700 to 1,000 °C temperatures, and hydrogen atmosphere needed in the standard chemical vapor deposition technique. Three lasers, whose pulses are coordinated by computer, supply energy for the deposition. The reaction milieu consists of variable proportions of carbon dioxide, which is the carbon source, and nitrogen. Robots guide the movement of the surface as the coating is applied. JANUARY 22,1996 C&EN
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