Thermochemistry of neutral and protonated 1,7,7-trimethylbicyclo[2.2.1]heptan-2-thione (thiocamphor)

The standard molar energy of combustion of 1,7,7-trimethylbicyclo[2.2.1]heptan-2-thione (thiocamphor), [53402-10-1], has been determined by using a rotary-bomb calorimeter. The vapour pressure of the compound was measured between the interval T = 261.96 K to T = 281.66 K, by the Knudsen-effusion technique. From the experimental results of this work, the standard molar enthalpies of combustion, sublimation and formation in the crystalline and gaseous state at the temperature of T = 298.15 K have been derived for thiocamphor: 1cH o m = −(6736.9 ± 3.3) kJ · mol−1; 1fH o m(cr) = −(86.8 ± 3.5) kJ · mol−1;1subHom = (61.7 ± 0.9) kJ · mol−1; and 1 fHom(g) = −(25.1 ± 3.6) kJ · mol−1. These results have been combined with their gas-phase proton affinities to yield the standard enthalpy of formation of the thiocamphor H+ species.The support of the Spanish D.G.E.S. under Project PB96-0927-C02-01 is gratefully acknowledged