06413_22 - W Wacker process A process for the manufacture...

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W Wacker process A process for the manufacture of ethanal by the air oxida- tion of ethene. A mixture of air and ethene is bubbled through a solution con- taining palladium(II) chloride and cop- per(II) chloride. The Pd 2+ ions form a complex with the ethene in which the ion is bound to the pi electrons in the C=C bond. This decreases the electron density in the bond, making it suscepti- ble to nucleophilic attack by water mol- ecules. The complex formed breaks down to ethanal and palladium metal. The Cu 2+ ions oxidize the palladium back to Pd 2+ , being reduced to Cu + ions in the process. The air present oxidizes Cu + back to Cu 2+ . Thus the copper(II) and palladium(II) ions effectively act as catalysts in the process, which is now the main source of ethanal and, by further oxidation, ethanoic acid. It can also be applied to other alkenes. It is named after Alexander von Wacker (1846–1922). Wallace, Alfred Russel (1823–1913) British naturalist, who in 1848 went on an expedition to the Amazon, and in 1854 travelled to the Malay Archipelago. There he noticed the differences between the animals of Asia and Australasia and devised * Wallace’s line, which separates them. This led him to develop a theory of * evolution through * natural selection, which coincided with the views of Charles * Darwin; their theories were pre- sented jointly to the Linnaean Society in 1858. Wallace’s line An imaginary line that runs between the Indonesian islands of Bali and Lombok and represents the sepa- ration of the Australian and Oriental fau- nas. It was proposed by Alfred Russel Wallace, who had noted that the mam- mals in SE Asia are different from and more advanced than their Australian counterparts. He suggested this was be- cause the Australian continent had split away from Asia before the better adapted placental mammals evolved in Asia. Hence the isolated Australian marsupials and monotremes were able to thrive while those in Asia were driven to extinc- tion by competition from placental mam- mals. See also zoogeography . wall effect Any effect resulting from the nature or presence of the inside wall of a container on the system it encloses. Walton, Ernest See cockcroft, sir john douglas . warfarin 3-(alpha-acetonylbenzyl)-4- hydroxycoumarin: a synthetic * anticoag- ulant used both therapeutically in clinical medicine and, in lethal doses, as a roden- ticide ( see pesticide ). warm-blooded animal See endo- therm . warm front See front . warning coloration (aposematic col- oration) The conspicuous markings of an animal that make it easily recognizable and warn would-be predators that it is a poisonous, foul-tasting, or dangerous species. For example, the yellow-and- black striped abdomen of the wasp warns of its sting. See also mimicry . washing soda
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This note was uploaded on 05/29/2009 for the course CIVIL ENG 12345 taught by Professor Xhfxfh during the Spring '09 term at Amirkabir University of Technology.

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06413_22 - W Wacker process A process for the manufacture...

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