Symmetrically subsituted epoxides give the same products in both the acid catalysed and base catalyzed ring opening. An unsymmetrical epoxide gives different products under acid catalysed and base catalysed conditions. Under basic contions, the alkoxide ion simply attacks the less hindered carbon atom in an `SN^(2)` displacement. Under acidic conditions, the alcohol, attacks the protonated epoxide.

Structure II and III show that the oxtrane carbon share part of positive charge. The tertiary carbon bear a larger part of positive charge and it is more strongly electrophilic. The bond between teritiary carbon and oxygen is weaker implying a lower transition state energy for attack at the teritary carbon. Attack by the weak nucleophilic is sensitive to the strength of electrophilic is sensitive to the strength of electrophile. Center attack takes place at more electrophilic carbon which is usually the more substituted carbon because it can better support the positive charge.

Options

A.
B.
C.
D. None

Answer

D