Chapter 10: Elimination Reactions

In E2 reactions, a strong base removes the β-proton in a single concerted step, favoring Zaitsev products (more substituted alkenes) unless a bulky base like t-BuOK or LDA is used, which favors Hofmann products (less substituted). The stereochemical outcome of E2 is both stereoselective and sometimes stereospecific, especially when only one β-hydrogen is present and antiperiplanar geometry is required—best visualized using Newman projections. In contrast, E1 reactions proceed via a carbocation intermediate and show less stereochemical control but still favor the Zaitsev product. E1 and SN1 often occur in tandem when weak bases and polar protic solvents are used. The final sections help students decide between substitution and elimination by evaluating reagent type (strong/weak nucleophile or base), substrate class (primary, secondary, tertiary), and reaction conditions. By applying all three analytical steps—reagent function, mechanism selection, and regio/stereochemical prediction—students can accurately forecast reaction outcomes and master elimination chemistry.