Step 1: Substrate assessment. The reactant is a benzylic tertiary bromide; such substrates strongly favor elimination because the resultant conjugated alkene is highly stabilized. Step 2: Base characteristics. Sodium tert-butoxide is a bulky, strong base whose steric bulk inhibits nucleophilic substitution while readily abstracting β-hydrogens. Step 3: Reaction pathway. An E2 mechanism operates, with the base removing a β-proton anti to the bromide leaving group, generating a double bond. Step 4: Product determination. Elimination yields a styrene-type conjugated alkene where the new double bond conjugates with the aromatic ring, providing maximum resonance stability. Step 5: Stability rationale. Conjugation with the benzene ring makes the alkene the dominant product over any substitution alternative. Step 6: Conclusion. The major product corresponds to option (3).
