Kinetics and mechanism of the osmium(VIII)-catalyzed oxidation of phosphite by hexacyanoferrate(III) ion in aqueous alkaline media

Kinetics and mechanism of electron transfer reactions. Osmium(VIII) catalyzed oxidation of mannitol by hexacyanoferrate(III) in aqueous alkaline medium

“…Similarly, the intercept from Figure 4 yielded k 2 as 7.1 · 10 )2 dm 3 mol )1 s )1 . Thus the value of K 1 is in agreement with the value reported earlier [18] and that calculated spectrophotometrically. Also, the reciprocal of Equation (12) can be re-arranged to Equation (16).…”

“…However, formaldehyde and CO 2 appeared to be the products on the basis of qualitative analysis. CO 2 , formaldehyde and formic acid as the products were also earlier reported [18].…”

“…Gupta and Mohan [18] reported that Beers' law was followed for the osmium (VIII) solution in the concentration range (5.0-30.0) · 10 )5 mol dm )3 at 340 nm. However, this law was observed to follow Beer's law at 350 nm with better results.…”

Kinetics and mechanisms of oxidation by metal ions, part XII [1] oxidation of formaldehyde by alkaline osmium(VIII)

“…The value of the equilibrium constant Kz, reaction 3, calculated in a similar manner from the second dissociation constant of osmic acid [15] (Kz, = 3 x comes out to be 16.6 which is in fair agreement with the value (24 5 4) found in solution of 1 mol dm-3 ionic strength (NaC1) [12]. Hence the only equilibrium of consequence in the formulation of mecha-nism is the equilibrium 3 and the choice of the reactive Os(VII1) species is restricted to HOSO~(OH)~and Oso4(OH)22because osmic acid has been shown to be inert towards the oxidation of formaldehyde (see description under spectral studies).…”

“…The absorbance is in arbitrary units. [ll] and 340 nm [12], and probably represent the maximum absorbance of the two osmium(VII1) species, HOSO~(OH)~-and os04(OH),2-, present in alkaline solution [7]. It is to be noted that in the reaction mixture the height of the peak appearing at 319 nm is lowered and the peak appearing at 346 nm disappeared from the spectra taken at the beginning of 22 ms after mixing.…”