Reaction mechanisms stable singlet carbenes

Whichever mechanism operates, it appears to be generally true that singlet aromatic carbenes react with the lower alcohols to form ethers at rates approaching the diffusion limit. On the other hand, aromatic carbenes that are clearly triplets do not give any ether at all from reaction with alcohols. Instead, these triplets behave as is expected of biradicals and abstract a hydrogen atom from the oxygen bearing carbon of the alcohol. The stable products of this reaction are those due to the combination and disproportionation (10) of the pair of radicals (Lapin et al., 1984). The more com-... 

So far we have considered only the most stable possible structure, singlet or triplet, of a given carbene. In real life, a carbene will be formed in a chemical reaction and may well be formed as the less stable of the alternatives. If a reaction occurs by an ionic mechanism on a molecule with all electrons... 

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