This organic chemistry lab video is the second video in a series and describes a Diels-Alder reaction lab experiment. The molecule 3-sulfolene (butadiene sulfone) cracks thermally to give 1,3-butadiene in-situ, which then reacts with the dienophile maleic anhydride. The Diels-Alder product is cis-1,2,3,6-tertahydrophthalic anhydride. This video describes setting up the reflux apparatus to carry out the reaction as well as isolating the product.