Nadic anhydride exhibits endo-exo isomerism.

In the exo isomer, the acid anhydride group points in the same direction towards the bridging carbon of the norbornene, while in the endo isomer the acid anhydride group points in the opposite direction.

[1][2] Commercially available nadic anhydride is mainly the endo isomer, as this is the isomer predominantly made in the Diels-Alder reaction in its synthesis.

[3] In the patent for the Diels-Alder reaction, nadic anhydride was given as an example of the reaction, made by the addition of maleic anhydride to cyclopentadiene, which gives mostly the endo isomer.

[4] Due to the reactivity of the norbornene moiety in the thiol-ene reaction, nadic anhydride is used in the synthesis of monomers for cross-linked polymer networks based on thiol-ene linkages.