Elimination Reactions Flashcards
Only elimination restriction
E1 CANT do 1° alkyl halide
E2 favored by:
High conc of a strong base and polar aprotic solvent (DMSO, DMF)
E1 favored by:
Weak base and a polar protic solvent (H2O, alcohol)
If using 1° alkyl halide, try using a… And why?
Bulky Base…
Because it makes it easier to pluck the H from CH3 and NOT the primary carbon
Zaitsev’s Rule
Most stable Alkene is one where double bond is most substituted
Order of reactivities of E2 alkyl halide reactions:
3° > 2° > 1°
Anti-Zaitsev accomplished by?
When base is sterically bulky, the most accessible proton is plucked to give least substituted alkene. (Under Kinetic control)
Best way to synthesize an Alkene… Using ____ and ______
Elimination;
Alkyl halides or alcohols
What Carbon is the H taken from in anti-zaitsev
Beta carbon
For E2, the H being removed and the halogen leaving must be…
Anti-coplanar
Can adjacent Equatorial substituents be anti-coplanar
No
What is required to dehydrate an alcohol to give an Alkene
Acid(Sulf/Phosp) and heat
What’s the purpose of the acid in acid catalyze do dehydration of an alcohol
The acid protonates OH to give a good leaving group(water). OH would be bad leaving group
What does the Hammond Postulate say
The transition state that leads to the 3° carbonation is lowest in energy
Milder way off dehydration of 1° and 2° alcohols
Use POCL3 and pyridine… Favors E2 and NO carbocation rearrangements
