Hydrogen peroxide catalysed decomposition

Decomposition of hydrogen peroxide, catalysed by manganese(iv) oxide - the effect of concentration and mass of catalyst on the rate and on the volume of product. 

To illustrate how a catalyst can decrease the activation energy for a reaction by providing another pathway for the reaction, let s look at the mechanism for the decomposition of hydrogen peroxide catalysed by the I ion. In the presence of this ion, the decomposition of H202 doesn t have to occur in a single step. It can occur in two... 

Hydrogen peroxide catalyses the reaction between [Cr(H20)6] and edta and the Cr i-edta complex accelerates the decomposition of the substrate. In the absence of edta, the analysis of the kinetic trace suggests that Cr v and/or Cr are catalysts for the decomposition reaction in acidic media. The rate of oxygen evolution decreases markedly in the presence of edta, suggesting that the complexes are less active catalysts for the decomposition process. Any catalytic edta-containing species are considered as having chromium in an oxidation state greater than +3. A detailed reaction scheme for the redox process may be simplified to include the reactions (ox=oxidation, sub=substitution) ... 

Heterogeneous catalysis occurs when the catalyst is in a different phase to the reaction mixture. For example, the decomposition of aqueous hydrogen peroxide catalysed by manganese(IV) oxide. 

On the industrial scale oxygen is obtained by the fractional distillation of air. A common laboratory method for the preparation of oxygen is by the decomposition of hydrogen peroxide. H Oj, a reaction catalysed by manganese(IV) oxide ... 

This is a disproportionation reaction, and is strongly catalysed by light and by a wide variety of materials, including many metals (for example copper and iron) especially if these materials have a large surface area. Some of these can induce explosive decomposition. Pure hydrogen peroxide can be kept in glass vessels in the dark, or in stone jars or in vessels made of pure aluminium with a smooth surface. 

Aqueous solutions of hydrogen peroxide decompose slowly the decomposition is catalysed by alkalis, by light and by heterogeneous catalysts, for example dust, platinum black and manganese... 

There are a lot of accidents involving the handling of hydrogen peroxide in partly rusted iron containers, which catalyse the explosive decomposition of peroxide. 

Metal catalyses the explosive decomposition of hydrogen peroxide. 

This oxide catalyses the violent or even explosive decomposition of hydrogen peroxide. This reaction explains the numerous accidents mentioned involving the contact of hydrogen peroxide with rusted iron. Two accidents of this nature dealt with mixtures of hydrogen peroxide with ammonia and an alkaline hydroxide The detonations took place after a period of induction of respectively several hours and four minutes. Iron (III) oxide also catalyses the explosive decomposition of calcium hypochlorite. 

Cobalt (II, CoO) and (111, C02O3) oxides catalyse the explosive decomposition of hydrogen peroxide. 

Nickei powder gives rise to dangerous reactions, which has led to accidents with potassium perchlorate (ignition), with chlorine at 600°C (ignition) and with ammonium nitrate at about 200°C (detonation). It catalyses the explosive decomposition of hydrogen peroxide. 

Lead oxide reacts violently with numerous metals such as sodium powder (immediate ignition), aluminium (thermite reaction, which is often explosive), zirconium (detonation), titanium, some metalloids, boron (incandescence by heating), boron-silicon or boron-aluminium mixtures (detonation in the last two cases). Finally, silicon gives rise to a violent reaction unless it is combined with aluminium (violent detonation). It also catalyses the explosive decomposition of hydrogen peroxide. 

Figure 10.25 Effect of phosphate stabiliser on Fe(m)-catalysed decomposition of hydrogen peroxide in absence of substrate [237]. Initial concentration 2.9 g/l H202, Phosphonate stabiliser 2 g/l, 95 °C, pH 12...

Frimer, A. A., J. Org. Chem., 1977, 42, 3194-3196, footnote 7 A new method of preparation involves interaction of ally lie halides in solvents with 98% hydrogen peroxide in presence of silver ion and base at ambient temperature under argon. The reactions must be run in the dark to prevent precipitation of metallic silver, which will catalyse decomposition of the hydroperoxide or excess hydrogen peroxide. In an experiment not run in the dark, the hydroperoxide from 3-chlorocyclohexene ignited spontaneously after isolation and concentration. 

The Bombardier beetle possesses, at the end of its abdomen, a combustion chamber that contains a hydroqui-none and hydrogen peroxide. When a predator approaches, the cells in the walls of the combustion chamber secrete two enzymes, catalase and peroxidase. Catalase causes decomposition of hydrogen peroxide to produce oxygen peroxidase catalyses the oxidation of the hydroquinone to produce a quinone. 

This is supplied as the solid in sealed ampoules or as a solution in water or 2-methylpropan-2-ol (t-butyl alcohol). It must be handled in a fume cupboard. It is extremely irritating and toxic and constitutes a severe eye injury hazard. The solution in t-butyl alcohol (Expt 5.47) must be prepared and dispensed in an efficient fume cupboard, with the added protection of gloves and goggles. This solution is reasonably stable (e.g. the decomposition after one month is about 20%), provided that no 2-methylprop-l-ene arising from the t-butyl alcohol is present as an impurity. Formation of black coloidal osmium, which can catalyse the decomposition of hydrogen peroxide, for example in the hydroxylation of alkenes, is rapid. 

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