Leaving Groups

The favorability of many reactions depends on the ability of the leaving group to be stable after it gains a negative charge. Sounds familiar, yes?

That’s because this is the same exact way we determine conjugate base stability.  

We use factors affecting acidity to determine which leaving groups will be most stable after gaining a lone pair.

  • Recall that the element effect consists of two trends: 

Example: Predict which of the following pairs of electrophiles possesses the best leaving group.

1m

Example: Predict which of the following pairs of electrophiles possesses the best leaving group.

1m

Example: Predict which of the following pairs of electrophiles possesses the best leaving group.

4m

Due to their high electronegativity, alkyl halides will be the primary leaving groups for this chapter.