Most current organic chemistry textbooks are organized by functional groups and those of us who teach organic chemistry use functional-group organization in our courses but ask students to learn organic chemistry from a mechanistic approach. To enrich and extend the chemical understanding and knowledge of pericyclic-type reactions for chemistry majors, we introduced into the chemistry-major organic chemistry laboratory a discovery-based, collaborative experiment on the thermal rearrangement of allylic sulfinates to thermodynamically more stable allylic sulfones. The sensitivity of the sulfinate-sulfone rearrangement pathway to substrate structure in this experiment allows the students to investigate the structure-reaction relationship of organic chemistry. Students also encounter the chemical and spectral properties of diasteromers and the necessity of deuterium labeling for product identification. (Contains 8 notes, 2 tables, 1 figure and 4 schemes.)