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]hep tan-2-thione (thiocamphor), [53402-10-1], has been determined by using a ro tary-bomb calorimeter. The vapour pressure of the compound was measured bet ween the interval T = 261.96 K to T = 281.66 K, by the Knudsen-effusion tec hnique. From the experimental results of this work, the standard molar enth alpies of combustion, sublimation and formation in the crystalline and gase ous state at the temperature of T = 298.15 K have been derived for thiocamp hor: Delta(C)H(m)(o) = -(6736.9 +/- 3.3) kJ.mol(-1); Delta(f)H(m)(o)(cr) (8 6.8 +/- 3.5) kJ.mol(-1); Delta(sub)H(m)(o) = (61.7 +/- 0.9) kJ.mol(-1); and Delta(f)H(m)(o)(g) = -(25.1 +/- 3.6) kJ.mol(-1). These results have been c ombined with their gas-phase proton affinities to yield the standard enthal py of formation of the thiocamphor H+ species. (C) 1999 Academic Press.