SCIENCE/TECHNOLOGY tery utilizing solid polymer electrolytes. Such electrolytes have been proposed as the medium for movement of lithium ions in the battery to alleviate some of the problems inherent in using organic liquid electrolytes. W. R. Grace, one of the world's largest producers of battery separators, pro vides expertise in chemical products and film making, especially in the area of thin-film polymer processing. Johnson Controls Battery Group, a major suppli er of automotive batteries, brings exper tise as a low-cost manufacturer and ex perience with high-voltage battery sys tems. SRI International contributes fundamental solid-polymer electrolyte technology, EIC Laboratories adds its cathode-materials development along with solid-polymer electrolyte exper tise, and UCAR Carbon brings exper tise in carbon-based materials. Under the CRADAs, the team will also receive technology from USABC-funded activ
ities at Sandia and Lawrence Berkeley national laboratories. The tentative Delco Remy/Valence Technology contract is for an ambienttemperature lithium-polymer system utilizing lithium metals as anode materi als, a vanadium-oxide-based system as the cathode, and a proprietary singlephase solid-state flexible polymer elec trolyte. Valence Technology owns the key patents and proprietary information and provides expertise in processing the materials into battery cells. Delco Remy will provide the technology to integrate the cells into battery systems. In the second type of advanced batter ies, the molten salt technology of the lithium (metal)-sulfide battery—an ele vated-temperature lithium alloy/molten salt/metal sulfide electrochemical sys tem—provides for high power capabili ty. This translates into better accelera tion. The technology was pioneered at Argonne during the 1970s.
Calorimetry bolsters vitamin Κ mechanism
Energy and power densities that may provide electric vehicles with perfor mance equal to that of today's internal combustion engine vehicles are among the advantages of the lithium (metal)sulfide battery. Other advantages in clude relatively small size and low weight, long life, a cost per kilowatthour similar to today's most inexpensive batteries, and low manufacturing costs. Moreover, the battery is composed of iron disulfide and Uthium-aluminum al loy, which USABC says are sensitive to environmental concerns and have the potential for complete recyclability. Under a three-year, $17.3 million contract from USABC, Saft America will pursue a bipolar form of the lithi um (aluminum)-iron disulfide battery first developed by Argonne. The com pany will have lead responsibility for module development tasks, with Ar gonne providing technical support. James Krieger
reduced to the hydroquinone by a re ductase enzyme. Such clot-preventing drugs as dicumarol and warfarin act by inhibiting this reduction step. Ionization of a hydronaphthoquinone proton would produce a base. But such a base would have a pKg (pKg is the nega-
The proposed role of vitamin Κ in blood mates serve as calcium binding sites clotting has gained support from calo during regulation of the cascade of clot rimetry measurements that show the ting reactions. heat of a key reaction in the mechanism Vitamin Κ is 2-methyl-3-phytyl-l,4to be what was expected [/. Am. Chem. naphthoquinone. To function, it must be Soc, 114, 9209 (1992)]. Though this finding is not a proof, it is an important test Reaction with oxygen amplifies strength of naphthoxide base that the theory has passed. In 1991, chemistry profes OH H Η sor Paul Dowd of the Uni versity of Pittsburgh sug CH 3 gested that reaction of oxy CH 3 gen with an anion of the HO Ο / HO O—CT C0 2 " reduced form of vitamin Κ Glutamate Vitamin Κ base vastly amplifies the basicity 02 of the anion, enabling that ^ co2 base to carboxylate gluta mate residues in blood-clot ting proteins. Vitamin-Kmediated carboxylation of glutamate had long been Η ° known; Dowd's contribu Reductase tion was how vitamin Κ ο manages to do it. co2 'CH3 Vitamin Κ finishes biosyn co 2" Ο Ο thesis of blood-clot promoters Vitamin Κ oxide γ-Car boxy glutamate Vitamin Κ prothrombin and factors VII, IX, and X, and of clot-inhibit ing proteins C and S by con CH CH verting 10 to 12 glutamate —CH2CH2CH2CH R= — C H C H = C — -CH residues in each of these Note: Tinted species represent compounds proteins to γ-carboxyglutawhose reactions were studied calorimetrically. mates. The γ-carboxygluta-
,λ
3
2
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tive logarithm of the dissociation constant) of only 9, v/hereas a pKa of 26 to 28 is needed to form a carbanion on the γ-carbon of glutamate for carboxylation. Working with graduate student Seung Wook Ham and postdoctoral fel low Roger Hershline and with support from the National Science Foundation, Dowd showed that bubbling oxygen through a solution of diethyl adipate and potassium 2,4-dimethyl-l-naphtholate (a model compound for vitamin K) in tetrahydrofuran produced a base strong enough to catalyze Dieckmann condensation of the adipate to ethyl cyclopentanone-2-carboxylate. The Dieckmann condensation was a stand-in for carboxylation of glutamate. This condensation normally requires a base as strong as ethoxide and the naphtholate alone was not strong enough. Oxidation must have done something to amplify the basicity of the naphtholate. As a way to provide a test of this mechanism, the Pittsburgh group con structed a thermochemical cycle of the mechanism and calculated the needed heat of reaction for each step and heat of formation for each intermediate from lit erature values for similar compounds and reactions. But one value was uncer tain. For the mechanism to be valid, the overall oxidation of 1-naphthol to 2,3epoxy-4-hydroxy-l-tetralone had to be exothermic by -52 kcal per mole. Enter organic chemistry professor Ed ward M. Arnett of Duke University. On a visit from Durham, N.C., to Pittsburgh, Arnett learned of the problem. Arnett re alized that he could construct a thermo chemical cycle of deprotonations (neu tralizations) and oxidations of model naphthol compounds whose heats could be measured calorimetrically and added up according to the first law of thermo dynamics to give an estimate of the key reaction in Dowd's mechanism. On his return to Duke, Arnett and postdoctoral fellow Robert A. Flowers II set to work to determine the measurable values. NSF supported this work also. The Durham investigators found a heat of reaction of -60 kcal per mole for oxi dation of 2,4-dimethyl- and of -53 kcal per mole for oxidation of 2,3,4-trimethyl1-naphthol to the epoxyhydroxytetralones as model compounds. The Duke and Pitt workers conclude that oxygen oxidation provides more than enough energy to give the needed base amplifi cation for carboxylation of glutamate. Stephen Stinson
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MAGOX Magnesium Oxide (MgO)
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Lime (CaO)
Unit Ratios of Common Neutralization Agents
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OH)2)
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