- 行业: Printing & publishing
- Number of terms: 178089
- Number of blossaries: 0
- Company Profile:
McGraw Hill Financial, Inc. is an American publicly traded corporation headquartered in Rockefeller Center in New York City. Its primary areas of business are financial, publishing, and business services.
A chemical reaction in which a sulfonic acid group, –SO<sub>3</sub>H, is introduced into the structure of a molecule or ion in place of a hydrogen atom.
Industry:Science
A chemical reaction in which many molecules undergo chemical reaction after one molecule becomes activated. In ordinary chemical reactions, every molecule that reacts must first become activated by collision with other rapidly moving molecules. The number of these violent collisions per second is so small that the reaction is slow. Once a chain reaction is started, it is not necessary to wait for more collisions with activated molecules to accelerate the reaction, which now proceeds spontaneously.
Industry:Science
A chemical reaction or process involving chelate ring formation and characterized by multiple coordinate bonding between two or more of the electron-pair-donor groups of a multidentate ligand and an electron-pair-acceptor metal ion. The multidentate ligand is usually called a chelating agent, and the product is known as a metal chelate compound or metal chelate complex. Metal chelate chemistry is a subdivision of coordination chemistry and is characterized by the special properties resulting from the utilization of ligands possessing bridged donor groups, two or more of which coordinate simultaneously to a metal ion.
Industry:Science
A chemical reaction or process which results in the formation of a chemical bond between a halogen atom and another atom. Reactions resulting in the formation of halogen-carbon bonds are especially important, and the emphasis in this article is primarily on such reactions. The halogenated compounds produced are employed in many ways, for example, as solvents, intermediates for numerous chemicals, plastic and polymer intermediates, insecticides, fumigants, sterilants, refrigerants, additives for gasoline, and materials used in fire extinguishers.
Industry:Science
A chemical reaction or series of reactions leading to the predominant or exclusive formation of a single enantiomer, that is, one of an isomeric pair of chemical compounds whose molecules are nonsuperimposable mirror images. Enantiomers are said to be chiral. Many organic compounds of interest for pharmaceuticals, flavorings, and pesticides are chiral. A specific target of an asymmetric synthesis is a product that contains only the desired enantiomer rather than a mixture of enantiomers of chiral molecules.
Industry:Science
A chemical reduction process which, once initiated, is autocatalytic. The process is similar to electroplating except that no outside current is needed. The metal ions are reduced by chemical agents in the plating solutions, and deposit on the substrate. Electroless plating is used for coating nonmetallic parts. Decorative electroless plates are usually further coated with electrodeposited nickel and chromium. There are also applications for electroless deposits on metallic substrates, especially when irregularly shaped objects require a uniform coating. Electroless copper is used extensively for printed circuits, which are produced either by coating the nonmetallic substrate with a very thin layer of electroless copper and electroplating to the desired thickness or by using the electroless process only. Electroless iron and cobalt have limited uses. Electroless gold is used for microcircuits and connections to solid-state components. Deeply recessed areas which are difficult to plate can be coated by the electroless process.
Industry:Science
A chemical substance that, when added to a liquid such as water, reduces the freezing point of the mixture. Antifreezes are used in a wide variety of applications, the most common being automotive cooling systems. Antifreeze liquids are also used in refrigeration systems (as a secondary coolant), heating and air-conditioning systems, ice skating rinks, and solar energy units, and as deicing agents for runways and aircraft.
Industry:Science
A chemical substance, usually containing a metallic ion, used to facilitate the fixing of a dye to a fiber. From the earliest days of dyeing, it was observed that for many natural dyes the color imparted to a fabric was enhanced and the fastness (resistance to fading or running) improved if the fabric was first treated with a solution containing a soluble metallic salt of chromium, aluminum, or copper. In the simplest process model, metal ions are incorporated on the surface and within the fibers of the fabric and, upon exposure to dye molecules at the appropriate pH and temperature, form colored metal-dye complexes. The metal ion is called a mordant. The complex formation process is called chelation, and can result in a fast and deeply colored fabric. One of the oldest mordant dyes is alizarin, derived from the root of the madder plant. Chemically, it is an anthraquinone derivative, and the dye color depends upon the metal with which it is complexed; with barium, a blue color is obtained, and with aluminum a rose-red.
Industry:Science
A chemical synthesis technique for preparing gels, glasses, and ceramic powders. The synthesis of materials by the sol-gel process generally involves the use of metal alkoxides, which undergo hydrolysis and condensation polymerization reactions to give gels (see <b>illustration</b>).
Industry:Science
