Manganates, formation

When it is impossible to establish the exact protonation state of the com-plex(es) in a specific reaction, or when all complexes in equilibrium over a broad pH range are under discussion, they will be written here as Mn TTHA, Mn TTHA, etc. The reactions of Mn TTHA complexes with H02-02" radicals were studied in solutions containing at least a twofold excess of TTHA to MnS04 and a tenfold excess of formate over TTHA, in order to ensure scavenging of the OH radical by formate and not TTHA. Under these conditions, only the mononuclear complexes described above were formed in significant yield. Studies were not carried out at pH < 2 because preliminary results indicated a complex reaction mechanism, hkely due to many different manganous complexes (various manganous formate complexes, aquo Mn ) in equilibrium. 

This is a way to do this procedure without having to use one of those crazy tube furnaces stuffed with thorium oxide or manganous oxide catalyst [21]. The key here is to use an excess of acetic anhydride. Using even more than the amount specified will insure that the reaction proceeds in the right direction and the bad side reaction formation of dibenzylketone will be minimalized (don t ask). 18g piperonylic acid or 13.6g phenylacetic acid, 50mL acetic anhydride and 50mU pyridine are refluxed for 6 hours and the solvent removed by vacuum distillation. The remaining residue is taken up in benzene or ether, washed with 10% NaOH solution (discard the water layer), and vacuum distilled to get 8g P2P (56%). 

In the early days of KMnO manufacture, the yield was only two-thhds of the theoretical the yield of NaAlnO never exceeded one-half theoretical. It is now known that the formation of manganate(VI) from Mn02 passes through a manganate(V) step. 

The reaction conditions favoring the formation of manganate(V) do not favor the oxidation of K.MnO to K MnO. This latter requites a lower temperature, lower KOH concentration, and higher H2O concentration. 

Under extremely alkaline conditions, pH > 12, potassium permanganate reacts involving a single-electron transfer, resulting in the formation of manganate (VI). 

At pH 13 the final products are manganate and cw-diol. The observation of a large degree of transfer of 0 from labelled MnO into oleate ion at pH 12 suggests formation of a cyclic ester, viz. 

Ammino - manganous Chlorides.—The anhydrous chloride absorbs ammonia gas rapidly at low temperature with formation of hexammino-manganous chloride, [Mn(NH3)6]Cl2, a pure white body which, on thermal decomposition, loses ammonia and is converted into the diammine, [Mn(NH8)2]Cl.2. There is also evidence of the existence of a monammine.2 All three substances are unstable and decompose on contact with water.3... 

Ammino-manganous Sulphates.—Anhydrous manganous sulphate slowly absorbs ammonia gas, increasing in volume with formation of hexammino-manganous sulphate, [Mn(XH3),.]S04. In vacuo it loses four molecules of ammonia and is transformed into the diarnmine, [Mn(NH3)JS04. The latter, however, seems incapable of reabsorbing ammonia to form the hexammine.2... 

Manganous salts unite with organic bases, generally with formation of di-derivatives. 

Although metal ions do not catalyze the decarboxylation of monocarboxylic acids in solution, a variety of metal ions catalyze the decarboxylation of oxaloacetic acid anion, leading to the formation of pyruvic acid (27). The metal ions involved were cupric, zinc, magnesium, aluminum, ferric, ferrous, manganous, and cadmium, approximately 10-2 to 10-3 M (27). Of these, the aluminum, ferric, ferrous, and cupric ions were the most efficient sodium, potassium, and silver ions were inactive. This process involves the decarboxylation of a / -keto acid, which undergoes a relatively facile uncatalyzed decarboxylation. However, not every decarboxylation of a / -keto acid is catalyzed by metal ions—only those... 

Formic acid solution reacts as follows 11) with hydroxides, oxides, carbonates, to form formates, e g., sodium formate, calcium formate, and with alcohols to form eslers (2) with silver of ammonio-silver nitrate to form metallic silver (3) with ferric formate solution, upon heating, to form red precipitalc of basic ferric formate (4) with mercuric chloride solution to form mercurous chloride, white precipitate and (SI with permanganate lin the presence of dilute H-SOj) to form CO and manganous salt solution. Formic acid causes painful wounds when it ennies in contact with the skin. At IhO C. formic acid yields CO plus H . When sodium formate is heated in vacuum at 300°C. H- and sodium oxalate are formed. With concentrated ll.SOj heated, sodium formate, or other formate, or formic aeid. yields carbon monoxide gas plus water. Sodium formate is made by healing NaOH and carbon monoxide under pressure at 2I0 C. 

Other typical reagents generated for coulometric titrations are hydrogen and hydroxyl ions, redox reagents such as ceric, cuprous, ferrous, chromate, ferric, manganic, stannous, and titanous ions, precipitation reagents such as silver, mercurous, mercuric, and sulfate ions, and complex-formation reagents such as cyanide ion and EDTA [8-10]. 

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