In organic chemistry we use the term leaving group to refer to a portion of a reactant that will depart the rest of the molecule as a result of reacting with another reagent. This occurs often in organic chemistry reactions. Notably in substitution and elimination reactions.
For example in the following SN2 reaction:
CH3CH2Br + ¯OH/DMF → CH3CH2OH
The leaving group is the Br. This is easy to notice because it has “left” the main reactant: CH3CH2Br Now OH is in the place of the Br hence this is a substitution reaction.
Common questions and answers:
So what makes a good leaving group “good”?
Answer: weak bases make good leaving groups
What are some examples of good leaving groups?