The details of the nitroxylation of 2-nitroxy-endo-tetrahydrodicyclope
ntadiene with nitric acid were studied. A bridged carbocation is sugge
sted as the intermediate responsible for the parallel and irreversible
formation of 2,6-dinitroxy-endo-tetrahydrodicyclopentadiene and 2,7-d
initroxy-1,7-trimethylenenorbomane.