SolutionsElimination of alcohols (dehydration)
1. Dehydration products
Give the major alkene from the acid dehydration of:
- 2-Butanol
- 2-Methyl-2-butanol
- 1-Methylcyclohexanol
- 2-Butene (mostly E), the most substituted alkene.
- 2-Methyl-2-butene.
- 1-Methylcyclohexene.
2. Ease
Order primary, secondary and tertiary alcohols from easiest to hardest to dehydrate. Why?
Tertiary > secondary > primary, because E1 goes through a carbocation and tertiary ones are the least unstable.
3. Rearrangement
Why does 3,3-dimethyl-2-butanol give 2,3-dimethyl-2-butene when heated with sulfuric acid?
The initial secondary carbocation rearranges by a methyl shift to the more stable tertiary carbocation, which loses a proton to give the tetrasubstituted alkene.