judithklinman，universityofcalifornia，berkeley(编辑修改稿)

judithklinman，universityofcalifornia，berkeley(编辑修改稿)内容摘要：

program to putionally discover, for example, doubly bridged dilithioacetylene and a dilithiocyclopropane with a planar tetracoordinate carbon. Octahedral CLi6, with six equivalent bonds to carbon, is one example of hypermetallation out of many. These predictions were verified, at least in part, experimentally. Such rulebreaking structures illustrate the interplay of ionic and covalent bonding with some LiLi interactions。 the octet rule is not violated. After my move to the University of ErlangenNuremberg in 1976, my coworkers added to the relatively small number of Xray structures. Each new result revealed some new feature, which required a detailed putational study to understand. This plexity is still true. Lithium pounds are selfassembling molecules par excellence. They can aggregate in a variety of ways and bind not only to polar solvents (the accelerators mentioned above) and to benzene, but also to the substrates before reaction. The witches brew also can be clarified putationally, as can the reaction pathways and transition states. Attacking the planar tetracoordinate carbon problem again, we took advantage of puter modeling to design promising chelated (internally solvated) anolithium pounds. Their subsequent synthesis and Xray analysis verified our prediction. A chemical world based on electrostatic interactions, rather than just covalent bonds, is disclosed by the geometries, the bonding, and the course of reactions of lithium pounds. A goal of science is not just to understand what has happened, but to predict the oute quantitatively. TIES THAT BIND Lithium pounds can display hypermetallation and an interplay of ionic and covalent bonding. Paul v. R. Schleyer is Graham Perdue Professor at the University of Geia and professor emeritus of the University of ErlangenNuremberg, in Germany. He was the first recipient of the ArfvedsonSchlenk Award of the Society of German Chemists sponsored by Chemetall. 6 LITHIUM AT A GLANCE Name: From the Greek lithos, stone. Atomic mass: . History: Discovered in 1817 by J. August Arfvedson in Stockholm. First isolated in 1821 by William T. Brande. Occurrence: Found in igneous rocks and many mineral spring waters. Appearance: Silvery white, soft metal. Behavior: Lithium is the lightest metal and is easily cut. It reacts slowly with water to form a colorless solution of LiOH and H2 and vigorously with all halogens to form halides. Uses: Lithium is used as a battery anode material. It is alloyed with aluminum and magnesium for lightweight, highperformance metals for aircraft. 7 SODIUM KNUT H. SCHR216。 DER, NORWEGIAN UNIVERSITY OF SCIENCE amp。 TECHNOLOGY Sodium is the seventh most abundant element in rocks and the fifth most abundant metal. It reacts with water and oxygen in the air, and in liquid ammonia it forms a blue solution described as solvated electrons. However, the sodium ion itself is quite inert, with high solubility for its salts and weak plexation abilities. For that reason, no classical analytical methods for the determination of sodium ions are available. Ionselective electrodes can be used, but they are not very adaptable. Emission spectroscopy (for example, flame photometry) is very convenient, and online and automatic continuous surveillance can be worked out. Sodium pounds are among the most frequently used materials for industrial and domestic use, and salt is needed for human life. For that reason, it has been of strategic importance in hot, humid tropical regions. Because of the inertness of the sodium ion, regular chemical reactions with sodium ions are limited, but sodium ions are essential to life for many reasons. The extracellular concentration of sodium ions in the human body and in animals is about 10 times higher than what is found inside the cells. This is not expected when passive diffusion through the cell membranes is considered. To keep that high gradient across a membrane requires energy, that is, an active transport using ATP. This is a means of energy storage for sudden use and for forming electrical potential gradients in nerve cells. A similar mechanism does not occur in plants, and this is one of the most important differentiating characteristics between animals and plants. Pure NaCl is NaCl, and for that reason all brands will be identical. However, some manufacturers claim their salt is saltier than regular table salt, and less salt should be required to obtain the proper salty taste of food. Obviously, in solution all brands of pure salts are identical, as the same amount of salt reaches the papillae on the tongue. However, if the salt is not dissolved when it passes the papillae, the sensing of the taste may be different because a quite concentrated solution is achieved on that spot. The physical shape of NaCl crystals differs from one producer to another, and this is important for dissolution in saliva. Soluble sodium salts are found in salt ores in several places on Earth。 among the most important salts are sodium chloride, carbonates, and trona [(Na3H(CO3)2 2H2O]. Of special interest are the salts in the ocean and in inland lakes such as the Great Salt Lake SALTY Lake Natron, in Tanzania, ishighly alkaline, containing soda (sodium carbonate), salt, and magnesite deposits. The drying soda forms white beds as water evaporates 8 (Utah), the Dead Sea, and the salt lakes in East Africa. The salts originate from the corrosion of silicates. The position of the different lakes, as well as the pH value of the waters, differs substantially from that of the ocean, with a weakly buffered pH value in the range of 8– to a relatively stable pH of for the carbonaterich lakes in East Africa. The latter is valid for all such lakes because such aqueous systems consist of both HCO32 and CO322, and this corresponds。