In an E2 elimination using a bulky base, which product is the Hofmann product?

• A. The less substituted alkene.
• B. The more substituted alkene.
• C. A mixture with equal amounts.
• D. A cyclic alkene.

Answer: (A)

The main idea here is how base size affects E2 regioselectivity. In an E2, the base removes a beta-hydrogen anti to the leaving group in a concerted step. A bulky base is sterically hindered, so it prefers the less hindered, less substituted beta-hydrogen. Abstracting that hydrogen leads to the less substituted double bond—the Hofmann product. Smaller bases, by contrast, can access the more hindered, more substituted beta-hydrogens more easily, giving the Zaitsev (more substituted) alkene. So, using a bulky base in E2 favors the less substituted alkene, which is why the Hofmann product is formed.