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The reaction 2 H 2 + O 2 → 2 H 2 O provides an example of chain branching. The propagation is a sequence of two steps whose net effect is to replace an H atom by another H atom plus two OH radicals. This leads to an explosion under certain conditions of temperature and pressure. [6] H• + O 2 → •OH + •O•
The Haber–Weiss reaction generates •OH (hydroxyl radicals) from H 2 O 2 (hydrogen peroxide) and superoxide (•O 2 −) catalyzed by iron ions. It was first proposed by Fritz Haber and his student Joseph Joshua Weiss in 1932.
An example of a simple chain reaction is the thermal decomposition of acetaldehyde (CH 3 CHO) to methane (CH 4) and carbon monoxide (CO). The experimental reaction order is 3/2, [4] which can be explained by a Rice-Herzfeld mechanism. [5] This reaction mechanism for acetaldehyde has 4 steps with rate equations for each step :
For example, at 2,200 °C (2,470 K; 3,990 °F) about three percent of all H 2 O are dissociated into various combinations of hydrogen and oxygen atoms, mostly H, H 2, O, O 2, and OH. Other reaction products like H 2 O 2 or HO 2 remain minor. At the very high temperature of 3,000 °C (3,270 K; 5,430 °F) more than half of the water molecules are ...
2H 2 O → O 2 + 4H + + 4e − Oxidation (generation of dioxygen) 4H + + 4e − → 2H 2 Reduction (generation of dihydrogen) 2H 2 O → 2H 2 + O 2 Total Reaction Of the two half reactions, the oxidation step is the most demanding because it requires the coupling of 4 electron and proton transfers and the formation of an oxygen-oxygen bond.
Converting a mixture of H 2 and CO into aliphatic products is a multi-step reaction with several intermediate compounds. The growth of the hydrocarbon chain may be visualized as involving a repeated sequence in which hydrogen atoms are added to carbon and oxygen, the C–O bond is split and a new C–C bond is formed.
(CH 2 CH 2)O + 2.5 O 2 → 2 CO 2 + 2 H 2 O, ΔH=−1223 kJ/mol. According to a kinetic analysis by Kilty and Sachtler, the following reactions describe the pathway leading to EO. In the first step, a superoxide (O 2 −) species is formed: [73] O 2 + Ag → Ag + O 2 −. This species reacts with ethylene Ag + O 2 − + H 2 C=CH 2 → (CH 2 CH ...
CaC 2 + 2 H 2 O → Ca(OH) 2 + C 2 H 2. This reaction was discovered by Friedrich Wöhler in 1862, [23] but a suitable commercial scale production method which allowed acetylene to be put into wider scale use was not found until 1892 by the Canadian inventor Thomas Willson while searching for a viable commercial production method for aluminum. [24]