Manganese dioxide, formation

Benzo[c]cinnoline (114) (3%) was separated from a complex mixture of colored products obtained from the oxidation of 9 with active manganese dioxide formation of 114 suggests the stepwise loss of nitrogen, 10- 113-+ 1, and 1,4-dipolar cycloaddition of benzyne to 113.16 Oxidation of 9 with (diacetoxyiodo)benzene gave azobenzene (4%), 1-phenylbenzotriazole (112)... 

Acetaldehyde [75-07-0] (ethanal), CH CHO, was first prepared by Scheele ia 1774, by the action of manganese dioxide [1313-13-9] and sulfuric acid [7664-93-9] on ethanol [64-17-5]. The stmcture of acetaldehyde was estabhshed in 1835 by Liebig from a pure sample prepared by oxidising ethyl alcohol with chromic acid. Liebig named the compound "aldehyde" from the Latin words translated as al(cohol) dehyd(rogenated). The formation of acetaldehyde by the addition of water [7732-18-5] to acetylene [74-86-2] was observed by Kutscherow] in 1881. 

The overall decomposition of solid potassium permanganate ia the temperature range of 250—300°C leads to the formation of a delta-manganese dioxide (shown ia brackets) and can be represented as follows ... 

The preparation of triaryknethane dyes proceeds through several stages formation of the colorless leuco base in acid media, conversion to the colorless carbinol base by using an oxidising agent, eg, lead dioxide, manganese dioxide, or alkah dichromates, and formation of the dye by treatment with acid (Fig. 1). The oxidation of the leuco base can also be accompHshed with atmospheric oxygen in the presence of catalysts. 

Knowledge of stoichiometry of the induced reaction could help to distinguish whether chromium(V) or chromium(IV) species are involved in the oxidation of benzaldehyde. Thus, the Cr(V) hypothesis predicts that for each molecule of benzaldehyde oxidized two molecules of manganese dioxide should be formed, whereas the Cr(IV) predicts that one molecule of manganese dioxide should be formed for each two molecules of benzaldehyde oxidized. Unfortunately, the attempt to determine the stoichiometry of the induced reaction failed because the oxidized manganese species was not precipitated during the reaction presumably due to formation of acetate complexes in the concentrated acetic acid solution. 

Depending on the composition of the active materials and on the manganese dioxide type employed, the OCV of freshly manufactured zinc-carbon cells with salt electrolyte varies between 1.55 and 1.85 V. It decreases during discharge and formation of the variable-composition mass. Upon prolonged storage of undischarged batteries, their OCV also decreases. 

Chemical/Physical. Alkali or alkaline earth metals dissolve in aniline with hydrogen evolution and the formation of anilides (Windholz et ah, 1983). Laha and Luthy (1990) investigated the redox reaction between aniline and a synthetic manganese dioxide in aqueous suspensions at the pH range 3.7-6.5. They postulated that aniline undergoes oxidation by loss of one electron forming cation radicals. These radicals may undergo head-to-tail, tail-to-tail, and head-to-head... 

Treatment of isopropyl 6-hydroxy-4-methoxymethyl-/3-carboline-3-carboxylate 189 with a primary amine in the presence of an excess of manganese dioxide produces the oxazolo[4,5-g]-/3-carboline 190 in moderate yield (Equation 125) <1998H(48)31>. The efficiency of the reaction is limited by the formation of by-products. 

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