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Journal of Physical Chemistry A, Vol.105, No.44, 10155-10168, 2001
meta-Benzyne reacts as an electrophile
Examination of gas-phase reactions of various nucleophiles with meta-benzyne analogues that carry a positively charged substituent has revealed that the meta-benzyne moiety is susceptible to nucleophilic attack. Addition of nucleophiles to the meta-benzyne moiety occurs rapidly without energy-demanding uncoupling of the singlet biradicals' formally unpaired electrons. The resulting zwitterionic intermediate may undergo fragmentation either by a homolytic bond cleavage to yield net-radical type products or by a heterolytic bond cleavage that generally leads to replacement of the original charged group with the incoming nucleophile. The intermediate was characterized experimentally and computationally and found to be a low-energy species. The nonradical reactivity reported here is common for meta-benzynes with positively charged substituents, and is predicted also to dominate the chemistry of anionic and neutral meta-benzynes.