High Energy Fuels I: A Novel Preparation of Exo-Tetrahydrodicyclopentadiene by Isomerization of Endo-Tetrahydrodicyclopentadiene

Endo-tetrahydrodicyclopentadiene (IV) is isomerized in the presence of trifluoromethanesulfonic acid (I) to give exo-tetrahydrodicyclopentadiene (V). At higher acid concentrations, the isomerization occurs instantaneously. The preferred molar ratio of I to IV is in the range 0.05 to 4.0 and the preferred temperature is in the range 20°C to 100°C. Under these conditions, virtually no admantane is formed and undesirable C₁₀H₁₆ isomers can be reduced to a minimum. Besides the homogeneous system, the acid catalyst also works in a two-phase heterogeneous system. The spent acid in the heterogeneous system can be reused without losing catalytic effectiveness.