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Wize University Organic Chemistry Textbook > Nucleophilic Substitutions and Elimination Reactions

Favouring Elimination over Subsitution

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Favouring Elimination over Subsitution


How do you decide if there will be an elimination reaction instead of a substitution reaction? There are some tips you can use:
  1. alcohols vs. alkoxides: alcohols (ROH) favour substitution reactions while alkoxides (NaOR) favour elimination reactions
  2. E2 vs. SN2: more substituted alkylhalides will favour elimination. Using a bulky base (KOtBu) will also favour elimination.
  3. E1 vs. SN1: adding heat and a strong acid (with the weak nucleophile) will favour elimination

Example: predict the products of the reactions shown below (point 1)





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Example: predict the products of the reactions shown below (point 2)




Example: predict the products of the reactions shown below (point 3)



Wize Tip
It is worth noting that elimination and substitution reactions usually happen in tandem in the real world. This is part of why they are so tricky!