The Interplay Between Substitution and Elimination

Many of the reagents commonly used as nucleophiles in substitution reactions are also bases, and they can thus promote elimination reactions. Since both elimination and substitution reactions commence from alkyl-LG species, it is not surprising that substitutions and eliminations are often competitive, and we gave some examples in Section 10.13.3. Now that we have considered both substitutions and eliminations, let s analyze the competition. 

Reactions of R-LG (where LG is a good leaving group) with 6 (a base and/or nucleophile) 

The interplay between nucleophilic substitution and elimination in 1°, T, and 3° systems. See the text for a discussion of certain exceptions and special cases. Adapted from a scheme presented in Kemp, D. S., and Vellaccio, F. (1980). Organic Chemistry, Worth Publishers, New York, pp. 227-228, 

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