What favors elimination reactions?

1 Answer
Apr 4, 2018

See below..


To promote elimination, the base should readily abstract a proton but not readily attack a carbon atom.

A bulky strong base, such as tert-butoxide enhances elimination.

Higher temperatures also favor elimination in most cases, because more molecules are formed, and #S < 0#.
As the temperature increases, the free energy term, ,becomes more negative and more favorable for elimination.

To promote substitution, we need a good nucleophile with limited basicity: a highly polarizable species that is the conjugate
base of a strong acid.

Bromide (#Br^-#) and iodide (#I^-#) are examples of good nucleophiles that are weak bases and favor substitution.

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