Characterization of Acidity on a Surface Contrasts with Molecular Fluorides

2 Characterization of Acidity on a Surface Contrasts with Molecular Fluorides 

One of the driving forces behind recent developments in the synthesis and characterization of new acids is the requirement to replace mineral acids by reagents and catalysts that will lead to reduction in waste, in other words to an improved atom economy. Thus, HCl used in the synthesis of diamino diphenyl methane, an intermediate in polyurethane production, can be replaced by a silico-aluminate catalyst in which the acid sites of the zeolite are accessible through the external surface. Less conventionally, simple aromatic hydrocarbons can be nitrated using 60-70% nitric acid in the presence of the strong Lewis acids, lanthanide-perfluoroalkane sulfonic acid salts, such as the ytterbium(lll) compounds (VI) and 

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