SolutionsEpoxide Ring Opening
1. Regiochemistry
Give the product of the ring opening of 2,2-dimethyloxirane with:
- CH3ONa in methanol
- Methanol with a small amount of H2SO4
- 1-Methoxy-2-methyl-2-propanol: in basic medium methoxide attacks the less hindered carbon (CH2).
- 2-Methoxy-2-methyl-1-propanol: in acidic medium methanol attacks the more substituted carbon, which better supports the positive charge.
2. Stereochemistry
What is the stereochemistry of the diol obtained by opening cyclohexene oxide with water in acidic medium?
trans-1,2-Cyclohexanediol (as a racemate): water attacks from the face opposite the epoxide oxygen, with inversion of the attacked carbon.
3. With organometallics
What is obtained when ethylene oxide is treated with ethylmagnesium bromide and then with dilute acid?
1-Butanol, CH3CH2CH2CH2OH: the organometallic opens the epoxide and the chain grows by two carbons.