Arynes radical ions

Two areas of aryne chemistry, aryne-metal complexes and aryne radical ions, have been omitted from this review. 

Aryne radical ions have been used mainly to deduce thermochemical information about neutral arynes although they also exhibit their own chemistry (H abstraction,... 

However, to include this enormous body of work, and the techniques that stand behind it, into the present chapter would surpass its limits. Hence, the reader is encouraged to visit the contributions on carbocations, carbanions, radicals, radical ions, carbenes, sylilenes, nitrenes, and arynes where studies involving frozen solutions will be referred to in their topical context. Thus, this chapter will deal only... 

Reactive intermediates " are believed to be transient intermediates in the majority of reactions. The main types of reactive intermediates of interest to organic chemists are carbocations, carbanions, radicals, radical ions, carbenes, nitrenes, arynes, nitrenium ions and diradicals. 

The anion-radical mechanism for these syntheses is based on the following facts. The reactions require photo- or electrochemical initiation. Oxygen inhibits the reactions totally, even with photoirradiation. Indoles are formed from o-iodoaniline only the meta isomer does not give rise to indole. Hence, the alternative aryne mechanism (cine-substitution) is not valid. What remains as a question is the validity of the ion-radical mechanism exclusively to the substitution of the acetonyl group for the halogen atom in o-haloareneamine or also for intramolecular condensation. 

Examples for frequently encountered intermediates in organic reactions are carbocations (carbenium ions, carbonium ions), carbanions, C-centered radicals, carbenes, O-centered radicals (hydroxyl, alkoxyl, peroxyl, superoxide anion radical etc.), nitrenes, N-centered radicals (aminium, iminium), arynes, to name but a few. Generally, with the exception of so-called persistent radicals which are stabilized by special steric or resonance effects, most radicals belong to the class of reactive intermediates. 

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