Free energy, styrene epoxidation

FIGURE 19.8 Free energy as a function of the reaction coordinate for the lowest activation energy path for epoxidation of styrene and formation of phenylacetaldehyde. 

The plausibility of the rate-limiting formation of III can be assessed by examining the linear free-energy relationship of log k2 and for the epoxidation of substituted styrenes by (BrgTPP)CrV(0)(X)51 and (+-TMP)FeiV(0), 6c which provide a slope of p+ = -1.9. Comparison with known rate-limiting carbocation formations via electrophilic additions to substituted styrenes show greater negative p+ values (-3.58 for hydration and -4.8 for... 

A drum of styrene oxide was punctured and the spillage absorbed into an hydrated silate absorbent, the combination swept up and drummed up for disposal. The drum became hot and started emitting copious white fumes. It was not possible to duplicate this behaviour in the laboratory unless acid or base catalyst was also present [1], Absorbents may be inert, epoxides are not but contain considerable strain energy which will be liberated by autoreaction or nucleophilic substitution by, e.g. water. Only a catalyst is needed neither silicates nor floor-sweepings can be guaranteed free of these [2]. 

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