Hofmann-type materials

Concepts in Crystal Engineering, p. 319 Crystal Engineering with Hydrogen Bonds, p. 357 Crystal Structure Prediction, p. 371 Cfystalline Microporous Silicas, p. 380 Dye Inclusion Crystals, p. 497 Hofmann-Type Clathrates, p. 645 Mineralomimetic Structures, p. 868 Molecular Squares, Boxes, and Cubes, p. 909 Organic Zeolites, p. 996 Soft/Smart Materials, p. 1302... 

Hofmann-type clathrates Werner clathrates clathrate hydrates inclusion compounds of urea, thiourea, and selenourea cyclodextrins calixarenes gossypol hexa-hosts hydroquinone phenol and Dianin s compounds graphite intercalates natural and pillared clays and others. Such studies contributed to the birth of supramolecular chemistry, with relevance to a new understanding of the world of materials that was emphasized with a Nobel Prize. 

The structure of a Hofmann type inclusion compounds is shown in scheme (C). The reaction of (HI) and (IV) with oxidants such as Fe + in water results in a color change from pale violet to black. When single crystals are used as starting materials, the resulting products, retain the original crystal shape (pseudomorphs), but they lose their single crystal nature and under SEM microscopic examination show small cracks and other defects. The proper formulation of the oxidation products would be [Ni(CN)2NH3] (polymer)(A)x y where polymer=polypyrrole, polyaniline ... 

Amides react with alkaline hypochlorite or hypobromite solutions to form primary amines having one less carbon atom. The reaction involves the hydrolysis of an isocyanate, which is seldom isolated. Isocyanates are also intermediates in the Curtius and Lossen rearrangements (methods 447 and 448). Although diese methods have a common mechanism and intermediate, they involve three separate and distinct types of starting materials and are, therefore, treated individually. A comparison of these reactions has been made. A detailed discussion of the Hofmann reaction, which includes conditions, typical procedures, and compounds prepared thereby, has been presented. ... 

Vulcanization is frequently done in two steps. After a preliminary vulcanization in a mold, a high-temperature (e.g., 180°C) postcure is carried out in air. The high-temperature postcure removes acidic materials that can catalyze hydrolytic decomposition of the vulcanizate (Roush et al., 1964). Also the high temperature enables the formation of additional crosslinks of the following type (Hofmann, 1967) ... 

The photolysis gave no detectable cyclized materials. The open chain products were either monomers or dimers of the intermediate N-propyl-N-(5-hexeny1)amino radical, presumably by the Hofmann-Loeffler type of rearrangement. 

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