B Displacement of fluorine and halogen from unsaturated carbon addition-elimination mechanism

B Displacement of fluorine and halogen from unsaturated carbon - addition-elimination mechanism 

If the addition stage is rate-limiting, which is usually the case, polarity of the bond to carbon is probably the most important factor governing the activation energy required, since fluorine is sometimes displaced more easily than chlorine or the other halogens. For example, benzoyl fluoride reacts more readily with hydroxide than the corresponding 

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