Key Concepts In Organic Chemistry: Haloalkanes Part II
-C-LG can undergo an elimination reaction, in addition to the substitution reactions already discussed. In
elimination reactions, the Nu: acts as a base (B) and attacks an H instead of attacking C as a nucleophile.
Because the H atom and the LG come off C atoms that are adjacent (often labelled α and β), this
reaction is called a β elimination.
-All species considered earlier as nucleophiles, can also act as bases (the only difference is whether the
species attacks a carbon or an H. We classify a group as a nucleophile or base depending on how it
reacts, not on what its structure is.
-There are two molecular features which act to increase the yield of elimination products at the expense
of substitution products: i) a large anion, and ii) a stable alkene as a product. By Zaitsev’s rule, the
alkene with the most alkyl groups will form in greater amounts.
-The E2 elimination mechanism is similar to the SN me2hanism. Elimination products by an E2