Halobenzenes deprotonation

Arynes are formed when haloarenes are treated with a strong base. Deprotonation at the ortho position of the halogen atom is favored because of polarity alternation, and the facility ofbenzyhe formation from halobenzene (PhF > PhCl > PhBr p Phi) also corresponds with the relative strength of the donor. 

Table 2 o-Deprotonation/electrophile quenching of halobenzene-CrfCOlj... 

When halobenzene derivatives are heated with powerful bases such as sodium amide, deprotonation is followed by elimination to give a benzyne, which reacts rapidly with the nucleophile. 

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