Identify the major product B in the following two-step reaction sequence:

Step-by-step solution

The given starting material is cyclopent-3-en-1-yl tosylate. In the first step, reaction with alcoholic KOH (a strong base) causes an E2 elimination of the tosylate group (-OTs) along with an adjacent proton. This elimination yields the conjugated diene 1,3-cyclopentadiene as product A. In the second step, bromoform ( CHBr₃ ) reacts with the strong base tert-butoxide ( t-BuO^- ) to undergo -elimination, generating the highly reactive electrophilic intermediate dibromocarbene ( :CBr₂ ). CHBr₃ + t-BuO^- :CBr₂ + t-BuO