Acid catalysis, general ethylene oxide

The synthesis of acetaldehyde by oxidation of ethylene, generally known as the Wacker process, was a major landmark in the application of homogeneous catalysis to industrial organic chemistry. It was also a major step in the displacement of acetylene (made from calcium carbide) as the feedstock for the manufacture of organic chemicals. Acetylene-based acetaldehyde was a major intermediate for production of acetic acid and butyraldehyde. However the cost was high because a large energy input is required to produce acetylene. The acetylene process still survives in a few East European countries and in Switzerland, where low cost acetylene is available. 

Oxidation of phenol by tris(l,10-phenanthroline)osmium(III) is second order in Os(III) and phenol and inverse second order in Os(II) and acidity. A mechanism is inferred in which the phenoxyl radical is produced through a rapid proton-coupled electron transfer (PCET) pre-equilibrium, followed by rate-limiting phenoxyl radical coupling. Application of Marcus theory indicated that the rate of electron transfer from phenoxide to osmium(III) is fast enough to account for the rapid PCET preequilibrium, but it did not rule out the intervention of other pathways such as concerted proton-electron transfer or general-base catalysis DFT studies, at B3LYP/LACVP level, of the oxidation of ethylene by osmium tetroxide, osmyl hydroxide, and osmyl chloride indicated that in the reaction of osmium tetroxide, the [3 4- 2] addition pathway leading to a five-membered metallacycle intermediate is more favourable than the [24-2] addition. The reaction with osmyl hydroxide is less favourable. In the reaction with osmyl chloride, the [24-2] addition pathway is more favourable than the [3 4-2] addition. ... 

---