Substitution and Elimination Reactions of Secondary Haloalkanes

Competing Substitution and Elimination Reactions of Secondary Haloalkanes 

Secondary haloalkanes can react by Sj 2, E2, S l, and El mechanisms, and it is sometimes difficult to predict which of these processes will occur in a given reaction. However, secondary haloalkanes tend to react with strong nucleophiles that are weak bases, such as thiolates or cyanide ion, by an process. 

On the other hand, a secondary haloalkane tends to react with weak nucleophiles that are also weak bases, like ethanol, by an mechanism with some accompanying El product. 

We can tip the scales in the other direction by adding sodium ethoxide to ethanol. By adding this strong base, we find that the product of the Sj l reaction drops to 18% of the total, and E2 products account for the rest. 

The reactions of secondary haloalkanes can proceed by Sj, E2, S l, and El mechanisms, depending on the reaction conditions. 

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