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Why do aryl halides usually react more slowly than alkyl halides?

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organohalogen compound Vinyl chloride is an organohalogen compound that has important industrial applications. When treated with certain catalysts, vinyl chloride monomers undergo polymerization and form the larger compound known as polyvinyl chloride, or PVC. PVC is used in the manufacture of numerous products, including packaging films and water pipes.

Aryl halides generally react more slowly than alkyl halides primarily because they possess significantly stronger carbon-halogen bonds. In chemistry, there is a rough correlation between bond strength and reaction rates: the stronger the carbon-halogen bond, the slower the rate of reaction.1

Furthermore, aryl halides are inherently resistant to standard nucleophilic substitution because the aromatic ring is not easily attacked by nucleophilic reagents unless it has been denuded of electrons by strongly electron-attracting substituents. While alkyl halides undergo conventional substitution pathways, simple aryl halides often require extreme conditions—such as very high temperatures—to react, and they frequently proceed through alternative mechanisms, such as the formation of a benzyne intermediate.23