HEAT OF FORMATION OF THE 2-NORBORNYL CATION IN THE GAS-PHASE

Proton transfer equilibria BH+ + 2-norbornene = B + 2-norbornyl+ and their temperature dependence were measured with a high-pressure mass spectrometer. The entropy change obtained from a van't Hoff plot of the equilibrium constant indicates that there is no rearrangement on protonation, i.e., that the product from the reaction is the 2-norbornyl cation. The enthalpy change, when connected to a proton affinity ladder, leads to a heat of formation of the norbornyl cation which is in very good agreement with the earlier results by Field and by Beauchamp. Compared to other secondary cyclic ions like cyclopentyl, norbornyl is unusually stable. © 1979, American Chemical Society. All rights reserved.