Why do elimination reactions compete with substitution reactions when alkyl halides react with a nucleophile?

1 Answer
Dr. Hayek
Oct 19, 2015

Not always!

Explanation:

Elimination reactions compete with substitution reactions because both reaction mechanisms favour the same conditions: Alkyl halide and a nucleophile.

Under some conditions, the elimination reactions cannot compete with substitution reactions because they cannot occur and vice versa.

Example on No Elimination reaction:
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The acetate #CH_3COO^-# is a strong nucleophile and a weak base, therefore, the substitution #S_(N1)# will occur at a very fast rate and consume all the alkyl halide before any elimination product is formed.

Example on No substitution reaction:
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The tert-butoxide #(CH_3)_3CO^-# is a strong bulky base and a weak nucleophile. The elimination will occur at a very fast rate and consume the alkyl halide before any substitution product is formed.

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