Iron: Difference between revisions
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An important type of change during beer staling, is caused by aroma active carbonyl compounds, which can be formed by radical reactions. | An important type of change during beer staling, is caused by aroma active carbonyl compounds, which can be formed by radical reactions. | ||
Since the investigations by Fenton published in the year 1894, it has been known that iron ions can catalytically promote oxidative reactions. In 1934, Haber and Weiss found final proof for the formation of radicals in aqueous solutions of bivalent iron and copper ions together with hydrogen peroxide and described the strongly oxidative character of these radicals. The formed radicals from both Fenton and Haber-Weiss schemes are extremely reactive and may give rise to radical chain reactions.<ref name="Zufall">Zufall, C., and Tyrell, Th. "The Influence of Heavy Metal Ions on Beer Flavour Stability." ''J. Inst. Brew.'', vol. 114, no. 2, 2008, pp. 134–142.</ref> | Since the investigations by Fenton published in the year 1894, it has been known that iron ions can catalytically promote oxidative reactions. In 1934, Haber and Weiss found final proof for the formation of radicals in aqueous solutions of bivalent iron and copper ions together with hydrogen peroxide and described the strongly oxidative character of these radicals. The formed radicals from both Fenton and Haber-Weiss schemes are extremely reactive and may give rise to radical chain reactions.<ref name="Zufall">Zufall, C., and Tyrell, Th. [https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.2050-0416.2008.tb00318.x "The Influence of Heavy Metal Ions on Beer Flavour Stability."] ''J. Inst. Brew.'', vol. 114, no. 2, 2008, pp. 134–142.</ref> | ||
;Chemical reactions | ;Chemical reactions | ||
Revision as of 08:18, 10 June 2020
An important type of change during beer staling, is caused by aroma active carbonyl compounds, which can be formed by radical reactions.
Since the investigations by Fenton published in the year 1894, it has been known that iron ions can catalytically promote oxidative reactions. In 1934, Haber and Weiss found final proof for the formation of radicals in aqueous solutions of bivalent iron and copper ions together with hydrogen peroxide and described the strongly oxidative character of these radicals. The formed radicals from both Fenton and Haber-Weiss schemes are extremely reactive and may give rise to radical chain reactions.[1]
- Chemical reactions
In the Fenton reaction, iron(II)-ions are oxidized to iron(III) by hydrogen peroxide, forming a hydroxyl radical and a hydroxyl ion. The iron(III) eventually reacts with a further molecule of hydrogen peroxide generating two protons and a superoxide radical. These superoxide radicals react with copper(II)-ions to copper(I) and oxygen in the Haber-Weiss scheme. The copper(I)-ion generated is capable of splitting a hydrogen peroxide molecule into a hydroxyl ion and a hydroxyl radical.[1]
See also
References
- ↑ a b Zufall, C., and Tyrell, Th. "The Influence of Heavy Metal Ions on Beer Flavour Stability." J. Inst. Brew., vol. 114, no. 2, 2008, pp. 134–142.