Oxidation, basic conditions manganese dioxide

According to reaction 15.47, for which the Nernst equation gives Eh = +0.401 V at pH 14.0, the oxidation of water is clearly favored by alkaline conditions (see Exercise 15.3). At the same time, however, many oxidation half-reactions also have lower Eh values in basic media. For example, Eh for the manganate/manganese dioxide couple... 

Native urine should be protected from light and stored at -20°C until processed. Oxidized urine sample can be stored at room temperature, but light protection is still recommended. Two procedures for the oxidation of urine (and other samples) are used (1) oxidation with manganese dioxide (Mn02) under acidic conditions, and (2) oxidation with iodine (iodine/potassium iodide, I2/KI) under acidic and basic conditions. The Mn02 oxidation method is a routine method used to quantify total pterins (fully oxidized neopterin, monapterin, biopterin, primapterin, isoxanthopterin, and pterin) the I2/KI method is used according to Fukushima and Nixon [11] for the differential oxidation of pterins and quantification of BH4. Total biopterin represents the sum of BH4, BH2, and fully oxidized biopterin. Under acidic conditions BH4 and BH2 are oxidized to biopterin, while under basic conditions only BH2 is oxidized to... 

The alkaline dry cell is a modified version of the Leclanche cell in which the acidic NH4C1 electrolyte of the Leclanche cell is replaced by a basic electrolyte, either NaOH or KOH. As in the Leclanche cell, the electrode reactions involve oxidation of zinc and reduction of manganese dioxide, but the oxidation product is zinc oxide, as is appropriate to the basic conditions ... 

The formation of benzimidazoles by cyclization of aryl amidines can be accomplished in a number of ways, but is usually carried out under anhydrous conditions in the presence of a base. Thus cyclizations of (45 R = OH) induced by benzenesulfonyl chloride in pyridine or triethylamine generally give yields of greater than 60%. The more direct process of oxidizing the parent compounds (45 R = H) with sodium hypochlorite under basic conditions gives even higher yields (70-98%). Intermediates in these reactions are the )V-haloamidines (45 R = C1) a nitrene intermediate may be involved or merely dehydrochlorination with concomitant cyclization (Scheme 25). Alternative cyclization procedures include oxidation of the parent amidines (45 R = H) by manganese dioxide or lead tetraacetate and thermal... 

The closure of the D-ring succeeded under basic conditions via an 8 2 displacement of the mesylate by the secondary amine (Scheme 16). Morphinan 106 was then successfully converted into thebaine (3) via manganese dioxide mediated oxidation following a procedure by Rapoport [67]. 

An efficient oxidizer with a high selectivity for allylic alcohols is manganese dioxide. Its reactivity depends largely on its preparation method, age, and activation. The best results are obtained from samples preactivated by sonication in water imder neutral or slightly basic conditions, which leads to morphological changes and a reproducibly activated reagent. The selectivity in favor of the allylic alcohols is retained and 1- or 2-octanol remain practically unreactive after sonication for 8 h at 17°C, or 30 min at 50°C.2i3... 

In addition to the exclusion of carbon dioxide, it is necessary to exclude oxygen from reactions where cations of the metal hydroxide layer are easily oxidized under basic conditions. LDHs of this type include manganese, cobalt (131) and iron in the divalent oxidation state, and vanadium in the trivalent state. Reactions involving these metal ions have formed LDHs with, for instance, Co " /Co and Fe " /Fe metal content, with the latter, known as green rust, being discussed earlier in Section II.J. 

Manganese hydroxide (ic) Methyl hydroxyethylcellulose Molybdenum Nickel carbonate, basic Sodium polyacrylate Talc Titanium dioxide Wollastonite Zinc oxide pigment, chalk markers Ultramarine blue pigment, chemical conditioning Kaolin... 

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