# What favors elimination reactions?

Apr 4, 2018

See below..

#### Explanation:

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 ($B {r}^{-}$) and iodide (${I}^{-}$) are examples of good nucleophiles that are weak bases and favor substitution.