Bimolecular elimination is our principal means for making alkenes.
- It is a concerted reaction, meaning that all of the bond breaking and bond making occurs in a single step.
- Recall the stereoelectronic requirement for an antiperiplanar arrangement of the groups to be lost.
The reaction can be viewed as a pair of "filled-empty" interactions:
- Filled orbital on base with empty s* of C-H bond
- Filled developing p-orbital with s* of C-X bond
The mechanism also occurs in the dehydration of primary alcohols and ethers.
E2 elimination is facilitated by dipolar aprotic solvents in which basicity is not reduced by solvation.
Remember the decision tree [CLICK] that summarizes the rules for deciding when SN2, SN1-E1, and E2 will occur.