Through the efforts of Alder and coworker, the structure was deduced in 1931.

The spontaneous dimerization of neat cyclopentadiene at room temperature to form dicyclopentadiene proceeds to around 50% conversion over 24 hours and yields the ''endo'' isomer in better than 99:1 ratio as the kinetically favored product (about 150:1 endo:exo at 80 °C). However, prolonged heating results in isomerization