The epoxide shown is treated with a catalytic amount of $H X_{2} SO X_{4}$ in methanol. Using the standard regiochemistry of acid-catalysed epoxide opening (the nucleophile attacks the carbon that better stabilises positive charge), which structure is the major product?

AStructure A
BStructure B
CStructure C
DStructure D

Answer: A

The compound is methyloxirane. Under acid catalysis the protonated epoxide opens with substantial positive charge on the more substituted carbon, so methanol attacks the secondary carbon, giving 2-methoxypropan-1-ol, COC(C)CO.

Practice Organic Reaction Mechanisms III: Nucleophilic Substitution More on Epoxide and ether cleavage regiochemistry on drawn structures

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The epoxide shown is treated with a catalytic amount of HX2​SOX4​ in methanol. Using the standard regiochemistry of acid-catalysed epoxide opening (the nucleophile attacks the carbon that better stabilises positive charge), which structure is the major product?

Answer: A

More questions on Epoxide and ether cleavage regiochemistry on drawn structures

The epoxide shown is treated with a catalytic amount of $H X_{2} SO X_{4}$ in methanol. Using the standard regiochemistry of acid-catalysed epoxide opening (the nucleophile attacks the carbon that better stabilises positive charge), which structure is the major product?