Manganese dioxides stabilization

The presence of the foreign cation stabilizes the crystal structure of a - Mn02 compounds. This manganese dioxide modification (more exactly it is not a real MnOz modification, since the structure contains a considerable proportion of foreign atoms) can be heated to relatively high temperatures (300 - 400 °C) without destruction of the lattice. Although Thackeray et al. reported the synthesis of cation-and water- free a - MnOz [49, 50J, which is reported to be stable up to 300 °C without destruction of the [2 x 2] tunnel structure, it is commonly believed that a small,... 

Oxidation of 1-aminobenzimidazoles with manganese dioxide or lead tetraacetate can give either 1,1 -azobenzimidazoles (735) or 3-substituted benzo-l,2,4-triazines (736). Electrochemical measurements have shown that the first step in this reaction is removal of an electron from a ir-orbital of benzimidazole rather than from the A-amino group. Because the cation radical which is formed must be stabilized by loss of a proton, for (736) to form the 2-substituent must contain an NH or OH group. This is unnecessary for the formation of the azo product (735) which may form via a nitrene intermediate. 

Van den Berg, C.M.G. and Kramer, 3.R., 1979. Determination of complexing capacities of ligands in natural waters and conditional stability constants of the copper complexes by means of manganese dioxide. Anal. Chim. Acta, 106 113-120. 

The methylene bridge in the fused oxazoline (203), 6-methyl-2//,6//-oxazolo[5,4,3-j/]quinolin-4-one, shows great stability towards acid cleavage, such as heating in 47% hydriodic acid. It is cleaved by oxidation, however, when treated with activated manganese dioxide in acetic acid (73JA5003). 

Oxalate stabilized with Fe(III) has been recommended for the determination of active oxygen in manganese dioxide. 

Manganese dioxide. 14, 200-201 I Wittig reaction. Allylic and stabilized ylides in the presence of >... 

Notably, the two geminal substituents on the cyclopropane ring stabilize both the norcaradiene and the bicyclo[2.1.0]pentane ( housane ) structure with respect to valence isomerization. The 3,3-dimethyl-3i/-pyrazoles mentioned above are prepared readily by 1,3-dipolar cycloaddition of 2-diazopropane to cyanoacetylenes. A more convenient synthesis of 4,5-dicyano-3,3-dimethyl-3//-pyrazole is the [3-1-2] cycloaddition of 2-diazopropane to fumarodinitrile, followed by oxidation of the 5,5-dimethyl-2-pyrazoline thus obtained with manganese dioxide. 

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