Orban oscillator

The Orban oscillator is based on a reaction of potassium thiocyanate with an alkaline hydrogen peroxide solution , which is catalyzed by copper (II) sulfate . The intermediate products formed in this reaction lead to feedback, which is a prerequisite for the oscillating reaction . There is a rhythmic color change between colorless and yellow-brown. This chemical clock was described in 1986 by Miklós Orbán , Eötvös University, Budapest (et al.).

Reaction equations

The overall equation for the reaction of potassium thiocyanate with hydrogen peroxide is:

{\ displaystyle \ mathrm {4 \; H_ {2} O_ {2} + SCN ^ {-} \ longrightarrow NH_ {4} ^ {+} + HSO_ {4} ^ {-} + HCO_ {3} ^ {- } + H_ {2} O}}

Hydrogen peroxide reacts in a disproportionation reaction with the copper ions from the copper (II) sulfate to form elemental oxygen and water.

{\ displaystyle \ mathrm {4 \; H_ {2} O_ {2} +5 \ Cu ^ {2 +} + 15 \ OH ^ {-} \ longrightarrow 5 \ [Cu (OH) _ {3}] ^ { -} + 2 \ O_ {2} +4 \ H_ {2} O}}

The entire reaction mechanism is very complex and consists of around 30 partial reactions.

Oscillating chemiluminescence with the Orban oscillator

If the Orban oscillator is combined with luminol , an oscillating chemiluminescence occurs under certain test conditions . Here luminol is oxidized with hydrogen peroxide via a copper (II) complex as a catalyst, with a rhythmic blue glow. The exact mechanism of the reaction is still unknown. If you also add a fluorophore , the color of the emitted light changes. Rhodamine B leads to a red-violet glow. Thiazole yellow provides a yellowish to green glow.

literature

H. Brandl, S. Albrecht, M. Haufe: New experiments on chemiluminescence, chemistry in our time, 27th year 1993, No. 6, pp. 303-305

Web links

University of Marburg: Experiments on chemiluminescence (PDF file; 5.29 MB)
Oscillating chemiluminescence with luminol

Individual evidence

↑ Elizabeth C. Edblom, Miklós Orbán, Irving R. Epstein: A New Iodate Oscillator: The Landolt Reaction with Ferrocyanide in a CSTR . In: J. Am. Chem. Soc. 1986 , 108 (11), pp. 2826-2830. doi : 10.1021 / ja00271a007

[1] Elizabeth C. Edblom, Miklós Orbán, Irving R. Epstein: A New Iodate Oscillator: The Landolt Reaction with Ferrocyanide in a CSTR . In: J. Am. Chem. Soc. 1986 , 108 (11), pp. 2826-2830. doi : 10.1021 / ja00271a007