Temperature Termination radical paths

The aziridination works for both aromatic and aliphatic olefins, including less active linear terminal olefins. Most reactions proceed in good yield at room temperature. The use of ci.v-stilbene at 0°C gives predominately cis aziridine product in about 90 10 cis trails ratio (Table 6.1). The conservation of cis structure suggests that a discrete silver nitrene intermediate is involved in the reaction path. Because of the unique disilver structure and unlikely formation of a silver(III) species, the authors suspect that a bridged nitrene intermediate between the two silver atoms may be responsible for this transformation in which each silver atom donates one electron to the nitrenoid. However, further research is necessary to prove this hypothesis and a fast radical reaction mechanism cannot be eliminated on the basis of current evidence. 

Certainly, the possibility of termination of chains by surface reactions cannot be disregarded. Several authors have discussed this possibility for ethane pyrolysis at lower temperatures (10). For example, chemisorption of hydrogen atom on a wall site could be followed by reaction by this site with an ethyl radical, forming ethane, which is later desorbed. More work will have to be done with reactors with different kinds of surfaces, with diffusion paths of different length, and with different surface/volume ratios, before even the qualitative aspects of the possible surface reactions are understood. 

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