Halogen acids, Properties Reactions

In addition to this work on charcoal- and silica-supported catalysts and on evaporated platinum films, a number of studies have been made on alumina-supported platinum catalysts (e.g., 111-114, 81,115) in which the aim has been the study of reactions at the platinum alone. In these cases, one cannot automatically dismiss the possibility of participation of the alumina support (i.e., of dual function behavior of the catalyst) because it is known that alumina may have acidic properties, particularly when retained halogen is present. In general terms, there is no immediate answer to this problem because the nature of this sort of catalyst wall be much dependent on the details of catalyst history, preparation, and use. However, there can be little doubt that in many experimental studies using plati-num/alumina, and in which the assumption has been made that the alumina support is inert, this assumption is essentially valid. For instance, one may note the inert alumina used by Davis and Venuto (111) and the justification provided by Gault et al. (116) for the inertness of the alumina used in a substantial body of previous work irrespective of whether the catalyst was... 

As esters the alkyl halides are hydrolysed by alkalis to alcohols and salts of halogen acids. They are converted by nascent hydrogen into hydrocarbons, by ammonia into amines, by alkoxides into ethers, by alkali hydrogen sulphides into mercaptans, by potassium cyanide into nitriles, and by sodium acetate into acetic esters. (Formulate these reactions.) The alkyl halides are practically insoluble in water but are, on the other hand, miscible with organic solvents. As a consequence of the great affinity of iodine for silver, the alkyl iodides are almost instantaneously decomposed by aqueous-alcoholic silver nitrate solution, and so yield silver iodide and alcohol. The important method of Ziesel for the quantitative determination of alkyl groups combined in the form of ethers, depends on this property (cf. p. 80). 

Chemical Properties.—Chemically the ethers are not very active nor do they lead to important derivatives. Chlorine forms substitution products in which, as in methyl ether, one to six hydrogens of the alkyl radicals are substituted. The halogen acids, especially hydriodic acid, form an alcohol by a reaction analogous to the reversion of the Williamson synthesis. 

As was stated, oleic acid occurs as an ester in many common fats and oils. In commoh with other unsaturated acids it possesses the characteristic property of forming addition products with the halogens or halogen acids. This property it imparts to the fats and oils in which it is present as an ester giving another important method for the analysis of these substances. This and the other properties and reactions of oleic acid which are important in connection with the analysis of fats and oils will be considered again when we study these substances. 

Lewis acids usually take the form MXn, where X is the ligand (a halogen atom, an amine or phosphine or another organic moiety). The metal is M and n is the normal valency of M. The acid MXn exhibits acidic properties in an equilibrium reaction ... 

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