Abstract
The reaction kinetics and mechanism of the oxidations of leucomethylene blue (MBH) and leucothionine (TH) by iron (III) sulfate in aqueous solution were studied spectrophotometrically by the stopped-flow technique. MBH and TH, which were freshly prepared by photoreduction of methylene blue and thionine, respectively, with ascorbic acid were used in the kinetic measurements. The pseudo-first-order rate constants (kobsd) show kinetic saturation at high initial concentrations of iron (III) sulfate for MBH and TH. It was found that the reciprocal of kobsd increases linearly with increase in the reciprocal of [Fe3+]0. A broad absorption band was observed on mixing MBH and Fe3+ solutions at low temperatures, and this was attributed to a charge-transfer complex between MBH and Fe3+. The effects of Fe2+ ion and L-(+)-ascorbic acid on the rates of oxidation were also investigated. A small kinetic isotope effect on the oxidation rate for MBH was observed. The results can be explained by a general mechanism with stepwise electron-proton-electron transfers with the formation of a complex between reactants.
| Original language | English |
|---|---|
| Pages (from-to) | 194-200 |
| Number of pages | 7 |
| Journal | Journal of Physical Organic Chemistry |
| Volume | 12 |
| Issue number | 3 |
| Publication status | Published - Mar 1999 |
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Keywords
- Hydride transfer
- Iron oxidation
- Kinetics and mechanism
- Leucomethylene blue
- Leucothionine
ASJC Scopus subject areas
- Organic Chemistry
- Physical and Theoretical Chemistry
Cite this
Kinetic studies on oxidations of leucomethylene blue and leucothionine by iron (III) in aqueous solution. / Liu, Yingjin; Yamamoto, Shunzo; Sueishi, Yoshimi.
In: Journal of Physical Organic Chemistry, Vol. 12, No. 3, 03.1999, p. 194-200.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Kinetic studies on oxidations of leucomethylene blue and leucothionine by iron (III) in aqueous solution
AU - Liu, Yingjin
AU - Yamamoto, Shunzo
AU - Sueishi, Yoshimi
PY - 1999/3
Y1 - 1999/3
N2 - The reaction kinetics and mechanism of the oxidations of leucomethylene blue (MBH) and leucothionine (TH) by iron (III) sulfate in aqueous solution were studied spectrophotometrically by the stopped-flow technique. MBH and TH, which were freshly prepared by photoreduction of methylene blue and thionine, respectively, with ascorbic acid were used in the kinetic measurements. The pseudo-first-order rate constants (kobsd) show kinetic saturation at high initial concentrations of iron (III) sulfate for MBH and TH. It was found that the reciprocal of kobsd increases linearly with increase in the reciprocal of [Fe3+]0. A broad absorption band was observed on mixing MBH and Fe3+ solutions at low temperatures, and this was attributed to a charge-transfer complex between MBH and Fe3+. The effects of Fe2+ ion and L-(+)-ascorbic acid on the rates of oxidation were also investigated. A small kinetic isotope effect on the oxidation rate for MBH was observed. The results can be explained by a general mechanism with stepwise electron-proton-electron transfers with the formation of a complex between reactants.
AB - The reaction kinetics and mechanism of the oxidations of leucomethylene blue (MBH) and leucothionine (TH) by iron (III) sulfate in aqueous solution were studied spectrophotometrically by the stopped-flow technique. MBH and TH, which were freshly prepared by photoreduction of methylene blue and thionine, respectively, with ascorbic acid were used in the kinetic measurements. The pseudo-first-order rate constants (kobsd) show kinetic saturation at high initial concentrations of iron (III) sulfate for MBH and TH. It was found that the reciprocal of kobsd increases linearly with increase in the reciprocal of [Fe3+]0. A broad absorption band was observed on mixing MBH and Fe3+ solutions at low temperatures, and this was attributed to a charge-transfer complex between MBH and Fe3+. The effects of Fe2+ ion and L-(+)-ascorbic acid on the rates of oxidation were also investigated. A small kinetic isotope effect on the oxidation rate for MBH was observed. The results can be explained by a general mechanism with stepwise electron-proton-electron transfers with the formation of a complex between reactants.
KW - Hydride transfer
KW - Iron oxidation
KW - Kinetics and mechanism
KW - Leucomethylene blue
KW - Leucothionine
UR - http://www.scopus.com/inward/record.url?scp=0013412740&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0013412740&partnerID=8YFLogxK
M3 - Article
VL - 12
SP - 194
EP - 200
JO - Journal of Physical Organic Chemistry
JF - Journal of Physical Organic Chemistry
SN - 0894-3230
IS - 3
ER -