Kinetics of Manganese(III) Acetate in Acetic Acid:  Generation of Mn(III) with Co(III), Ce(IV), and Dibromide Radicals; Reactions of Mn(III) with Mn(II), Co(II), Hydrogen Bromide, and Alkali Bromides

Abstract

The reaction of cobalt(III) acetate with excess manganese(II) acetate in acetic acid occurs in two stages, since the two forms Co(IIIc) and Co(IIIs) are not rapidly equilibrated and thus react independently. The rate constants at 24.5 degrees C are kc = 37.1 +/- 0.6 L mol-1 s-1 and ks = 6.8 +/- 0.2 L mol-1 s-1 at 24.5 degrees C in glacial acetic acid. The Mn(III) produced forms a dinuclear complex with the excess of Mn(II). This was studied independently and is characterized by the rate constant (3.43 +/- 0.01) x 10(2) L mol-1 s-1 at 24.5 degrees C. A similar interaction between Mn(III) and Co(II) is substantially slower, with k = (3.73 +/- 0.05) x 10(-1) L mol-1 s-1 at 24.5 degrees C. Mn(II) is also oxidized by Ce(IV), according to the rate law -d[Ce(IV)]/dt = k[Mn(II)]2[Ce(IV)], where k = (6.0 +/- 0.2) x 10(4) L2 mol-2 s-1. The reaction between Mn(II) and HBr2., believed to be involved in the mechanism by which Mn(III) oxidizes HBr, was studied by laser photolysis; the rate constant is (1.48 +/- 0.04) x 10(8) L mol-1 s-1 at approximately 23 degrees C in HOAc. Oxidation of Co(II) by HBr2. has the rate constant (3.0 +/- 0.1) x 10(7) L mol-1 s-1. The oxidation of HBr by Mn(III) is second order with respect to [HBr]; k = (4.10 +/- 0.08) x 10(5) L2 mol-2 s-1 at 4.5 degrees C in 10% aqueous HOAc. Similar reactions with alkali metal bromides were studied; their rate constants are 17-23 times smaller. This noncomplementary reaction is believed to follow that rate law so that HBr2. and not Br. (higher in Gibbs energy by 0.3 V) can serve as the intermediate. The analysis of the reaction steps then requires that the oxidation of HBr2. to Br2 by Mn(III) be diffusion controlled, which is consistent with the driving force and seemingly minor reorganization.

A Comprehensive Study of the Mechanism of Formation of Polyol-Made Hausmannite Nanoparticles: From Molecular Species to Solid Precipitation

“…Moreover, note that the structure of Mn III acetate is not well-established. The crystals resulting from the dehydration of Mn­(OAc) 3 ·2H 2 O have the [Mn 3 O­(OAc) 6 (HOAc)­(OAc)] n formula, and the three metal atoms are connected by three pairs of acetate bridges . In the Mn II Mn III complexes obtained by Hendrickson et al, two acetate ions are bridged to the two manganese centers. , …”

Preparation and characterization of manganese(iv) in aqueous acetic acid

“…Literature data are available in 90% AcOH for the reaction of NaBr with Mn(III) that was generated by oxidation of Mn(II) acetate with Ce(IV). 5 This method was suggested to generate monomeric Mn(III), as opposed to commercial samples which are believed to contain dimeric, acetate-bridged Mn(III). 5, 22 We have now examined the oxidation of bromide with a sample of Mn(III) produced in the Mn(IV)/Mn(II) reaction, in part to establish how the reactivity of this Mn(III) compares with that generated by other This journal is © The Royal Society of Chemistry 2010 methods.…”

“…The kinetics obeyed the mixed third order rate law of eqn (10), which has the same form as that reported earlier in 90% AcOH. 5 The second-order dependence on [Br -] is illustrated in Fig. 6.…”

Kinetics and activation energy of the oxidation of para‐tolyl radical by cobalt(III) in acetic acid: Competition kinetics

“…Much is known about the steps involved in the overall reaction which need not be repeated here except as pertinent to this investigation [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16].…”

“…Minor levels of intensely colored intermediates can be deleterious if they have high molar absorptivities at visible wavelengths. Among these is 2,6-dicarboxyanthraquinone, which is formed by oxidation of a benzylic cation as in this sequence: (1) The benzylic cation may result from the oxidation of a radical precursor by an active cobalt(III) intermediate, in competition with its very rapid reaction * [17] with oxygen:…”