when sulfur dioxide reacts with butadiene and isoprene, two different products result. the reaction mechanism will control what gets made. a kinetic product and a thermodynamic product are both possible. more of the thermodynamic product gets made than the kinetic product. the kinetic product comes from a diels–alder reaction, while a cheletropic reaction makes a more thermodynamically stable product. the cheletropic pathway is used more because it makes to a more stable five-membered ring adduct. the scheme below shows the difference between the two products. the path to the left shows the thermodynamic product, while the path to the right shows the kinetic product. suarez and sordo showed this in 1995. they showed this both with experiments and using gaussian calculations.