Stereochemistry of Diels-Alder Reactions Thermodynamic vs. Kinetic Control

Stereochemistry of Diels-Alder Reactions. Thermodynamic vs. Kinetic Control 

Chemical reactions often yield entirely different product distributions depending on the conditions under which they are carried out. In particular, high temperatures and long reaction times favor the most stable ( thermodynamic ) products, while low temperatures and short reaction times favor the most easily formed ( kinetic ) products. 

Consider Diels-Alder reaction of cyclopentadiene and maleic anhydride, leading to endo or exo adducts. 

Display space-filling models of endo adduct and exo adduct. Which appears to be the less crowded Identify specific interactions which disfavor the higher-energy adduct. Next, compare energies of the two adducts. Which is the more stable Were the reaction under thermodynamic control, which would be the major product and what would be the ratio of major to minor products Use equation (1). 

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