Epoxide opening [acidic conditions]

Epoxide opening [acidic conditions] Definition:

When acid is added to epoxides, nucleophiles will add to the more substitution position. The stereochemistry of this addition is trans.

Epoxide opening [acidic conditions] Explained:

Epoxides can open three-membered ring and this can be achieved with base or acid. As an acid can be used hydrogen halide acid (HCl, HBr, HI). As other nucleophiles can be used water or alcohol with a small amount of acid (often sulfuric acid) which catalyzes the reaction.

This mechanism involves two steps:

STEP 1. Proton transfer – epoxide is protonated by acid

STEP 2. Nucleophilic attack by halide ion via S_N2 process