MEETING BRIEFS FROM MIAMI BEACH
Mild ester hydrolysis developed Lithium hydroxide in 30% hydrogen peroxide hydrolyzes esters rapidly in high yields under mild conditions, according to senior research scientist Hemant K. Misra of the University of Massachusetts Medical Center, Worcester. Working with research director Donald J. Hnatowich, Misra got 90% yields, usually in 30 minutes to two hours at room temperature, though some esters needed six hours. They tried the method on a wide variety of aliphatic, aromatic, and heterocyclic esters, some containing disulfide bonds or imine (R2C=NR) groups. And lithium hydroperoxide is less expensive, drastic, and noxious than such alternatives as boron trihalides, trifluoroacetic acid, potassium thiocyanate in dimethylformamide, thiolates, or trialkylsilyl halides with iodine. The research was supported by the National Institutes of Health and Centocor. Tris(trimethylsilyl)methyl reagents made Photobromination of neat tris(trimethylsilyl)methane at 190 to 200 °C gives 75% yields of the bromide in just three hours, says organic chemistry professor Clifford L. Smith of Albany State College, Ga. Chemists value tris(trimethylsilyl)methyl groups because they impart thermal and chemical stability when attached to such atoms as mercury, zinc, cadmium, silicon, and phosphorus. In research supported by the National Institutes of Health, Smith and undergraduate Leslie James also converted the bromide in 75% yields each to the lithium and Grignard reagents, both by interchange with methyllithium, phenyllithium, or phenylmagnesium bromide and by reaction with lithium or magnesium in ether in the presence of ethylene dibromide. Their further work includes exploring reactivities of these organometallics. Ortho magnesiation achieved Magnesium amides give ortho metallation with many advantages over lithium reagents, says organic chemistry professor Philip E. Eaton of the University of Chicago. Working with graduate student Chih-Hung Lee and postdoctoral fellow Yusheng Xiong, he reacted methyl benzoate with bis(2,2,6,6tetramethylpiperidinyl)magnesium followed by carbon dioxide and diazomethane to get dimethyl phthalate with no attack of the amide reagent on the first ester group. The same amide reagent or bis(diisopropylamino)magnesium with Λ/,Λ/,Λ/',Λ/'tetraethylterephthalamide gave the dimethyl ester bis(diethylamide) of pyromellitic acid in one dimagnesiation step. Unlike lithium reagents, magnesium amides are stable in boiling tetrahydrofuran. Their work was supported by the National Institutes of Health and Office of Naval Research. Methods alkylate cyclopentadiene Two methods to make polyalkylcyclopentadienes have been devised by organic chemists Clifford G. Venier and Edward W. Casserly of Pennzoil Products Co., The Woodlands, Tex. Alkylated cyclopentadienes are difficult to make and may find use in organometallic compounds. In their phase-transfer catalytic method, for example, fe/t-butyl halides with sodium or potassium hydroxide and methyltrialkylammonium catalyst gave successively 1-ferf-butyl-, 1,3-di-ferf-butyl-, and 1,3,5tri-fert-butylcyclopentadiene. Their alcohol-based method with 52
September 25, 1989 C&EN
1-decanol and potassium decanoxide gave successively 1,3-didecyl-, 1,2,4-tridecyl-, 1,2,3,4-tetradecyl-, and 1,2,3,4,5pentadecylcyclopentadienes. Neither of their methods has yet produced pentamethylcyclopentadiene, which is the most popular derivative among organometallic chemists. Storage conditions affect rice stickiness If rice becomes sticky after it's cooked, it might be because it was stored at low temperatures, according to Joseph Chrastil, a chemist at the U.S. Department of Agriculture's research center in New Orleans. He notes that the stickiness of rice is determined in part by interactions that take place between proteins and starch. The higher the molecular weights of the compounds, the less interaction takes place. Stored for a year at 40 °C, protein molecular weight doubles and the molecular weight of starch molecules increases 20%. Rice so stored tends to be less sticky; however, rice stored at that temperature tends to turn yellow, which doesn't appeal to consumers, Chrastil notes. In rice stored at 4 °C, in contrast, the molecular weight of the proteins increased only 4 % , the molecular weight of the starch 10%. Thus, more binding between starch and protein takes place at 4 °C, with stickier cooked rice as a result. However, the degree of interaction is still lower than in fresh, unstored rice. ELISA methods developed for herbicides Some modern herbicides, such as chlorsulfuron, may be applied at such low rates (less than 1 oz per acre) that they can't be detected in groundwater by traditional analytical methods, says Du Pont chemist Janice K. Sharp. However, enzyme-linked immunosorbent assay (ELISA) techniques— long used in clinical applications—are now being adapted to pesticide analysis. In the case of chlorsulfuron, for example, the ELISA technique can measure as low as 10 ppt in water and 25 to 50 ppt in soil. The test is very specific, with no appreciable crossreactivity with related sulfonylureas or soil metabolites. The assay requires only one day. Because little sample workup is needed, one technician can process 25 to 50 or even more samples per day. 'This is a great improvement over traditional analytical methodologies which require extensive cleanup of water or soil extracts," Sharp notes. New polymer consists of random germanium network A new type of polymer consisting of a random network of sigma-bonded germanium atoms shows spectral properties reminiscent of solubilized semiconductor clusters, according to Patricia A. Bianconi, assistant professor of chemistry at Pennsylvania State University, University Park. The new polymers, called polygermynes, appear to have the same kind of structure as polysilynes, silicon-backbone polymers that Bianconi first synthesized while working with Timothy W. Weidman at AT&T Bell Labs (C&EN, Jan. 2, page 32). Polygermynes have the formula [RGe]n, where R is an alkyl or aryl group. They begin absorbing at about 800 nm— compared with 450 nm for polysilynes—and they have a higher extinction coefficient. This absorption accounts for the coffeelike color of polygermyne solutions, Bianconi says,
MEETING BRIEFS FROM MIAMI BEACH
and suggests the polymer is "acting as clusters of solubilized germanium." In addition, the polygermynes may be photopatternable, like polysilynes, because they can be photooxidized to give crosslinked networks of germanoxanes, [RGe015]n. Bianconi and undergraduate coworker Walter J. Szymanski also have made silyne/germyne copolymers. These display the properties of both homopolymers, suggesting that it may be possible to tailor the properties of inorganic networks by synthetically adjusting the backbone composition. Classification scheme aids chiral separations The classification of chiral stationary phases (CSPs) for HPLC separation of enantiomers into five groups eases method development for the chromatographer, says Irving W. Wainer, director of analytical chemistry at St. Jude Children's Research Hospital, Memphis, Tenn. Because enantiomers have identical physical properties (aside from the direction of rotation of polarized light), they cannot be resolved using standard chromatographic techniques. However, diastereomers do differ physically and separations can therefore be made via formation of transient, on-column diastereomeric complexes between enantiomeric solutes and chiral selectors on a CSP. Classification of CSPs can be based on different ways solute-CSP diastereomeric complexes are formed. Methods development is facilitated by using this scheme to decide where to begin. Enantioselective methods developed recently in Wainer's lab include one in which a coupled achiral/chiral HPLC system (with a CSP based on the serum protein oxacid glycoprotein) was used to separate verapamil, an antiarrhythmic agent. Multidisciplinary science and society course A multidisciplinary "Science, Technology, and Society" course at Florida State University confronts students with ethical and legal perspectives inherent in dealing with scientific and technological enterprise, according to Penny Gilmer, an associate professor of chemistry at FSU who developed the course. Besides Gilmer and constructor biology professor Paul Elliott, 10 faculty and administrators participated in developing topics for the spring term. Topics have included "Ethics in Science," by Gilmer; "AIDS: Public Policy and Public Health" by Elliott; and "Bioethics of Using Fetal Tissue" by philosophy professor Alan Mabe. Other topics have included the new reproductive technologies, gene therapy, and scientific freedom and responsibility. The course is offered once a year. Students choosing the course are mostly undergraduate seniors, about half a cross-section of science majors, and the rest from varied nonscience fields. Crab shell derivative prevents flavor loss A substance made from crab shells can be mixed with meat to prevent loss of flavor, according to John R. Vercellotti and Allen J. St. Angelo of the Department of Agriculture's Southern Regional Research Center in New Orleans. The substance, A/-carboxymethylchitosan (NCMC), is made from chitin, which is found in the shells of crabs, shrimp, lobsters, and other crustaceans. The chitin is first treated with a hot caustic solution, converting it to chitosan. Further treatment converts
it to NCMC. NCMC works in meat by chelating iron, thus inhibiting iron-catalyzed free radical oxidation reactions that break down polyunsaturated phospholipids. Phospholipids enhance the flavor of meat and provide acceptable texture. However, phospholipid oxidation products—which form in poorly refrigerated raw meats or cooked meats that have been reheated—have very distinctive off-flavors. Vercellotti and St. Angelo had a panel of volunteers taste warmed-over meats, both untreated and treated with NCMC, to provide feedback about flavor deterioration. The panel found that meat treated with NCMC tastes better than untreated meat. Greater use of expert systems at EPA seen "Expert systems will in time become an integral and widely used tool in most all aspects of the [Environmental Protection] Agency's regulatory mission," according to Daniel Greathouse of EPA's risk reduction engineering laboratory in Cincinnati, and James Decker of Computer Sciences Corp., Cincinnati. Expert systems are not currently being used as mainstream decision-making tools within the agency. In fact, says Greathouse, many EPA officials are unfamiliar with abstract expert system concepts and skeptical about the capabilities of these systems to provide meaningful and reliable advice. "Moreover," he says, "the value of knowledge systems technology has yet to be conclusively demonstrated through implementation of a wide-ranging application in the regulatory realm of the agency." Nevertheless, he foresees future adoption of expert systems within EPA for a number of applications. These include communicating information on new technologies, regulations, and policies to agency employees and facilitating employee training, especially for operations (such as the Superfund program) in which personnel turnover is high. "We expect that eventually expert system software and applications will become as prevalent as database, spreadsheet, and word processing software," he says. Focused goals crucial to business startups '•Most of the 2% of businesses that survive were predetermined at their beginning by proper examination of reality," says Stuart Marson, cofounder of Molecular Design Ltd., to would-be chemical information entrepreneurs. An entrepreneur must be able to recognize opportunities, rank them in order of importance, isolate the best, decide which play to his or her strengths, and determine if solving a particular problem is grounds for a new business. Being in the right place at the right time is not important—"We are all in the same place at the same time," he says. Instead, success depends primarily on the ability to perceive opportunities and then pursue them vigorously. However, he warns, personality traits that make an entrepreneur valuable in the beginning can cause corporate downfall once the business is mature. "In the beginning, listen only to yourself," he says. "After stabilization of the business, choose trusted advisers. But after becoming established, let others make decisions while you advise." Marson recently started another new business, Technology Resource (Kensington, Calif.), involving optical disc-based technologies. September 25, 1989 C&EN
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