The standard enthalpy of formation of the 1-adamantyl cation in the gas phase. An experimental and ab initio re-assessment

The standard molar enthalpy of formation of gaseous 1-adamantyl chloride (1 Cl,g) was determined experimentally by means of thermochemical techniques. Ab initio quantum-chemical calculations at the G2(MP2) level were performed on adamantyl cation (1(+)) and on 1Cl. Combination of these data with othe r experimental and computational results for adamantane (1H), isobutane (2H ), tert-butyl cation (2(+)), and tert-butyl chloride (2Cl) provided purely experimental and purely computational, independent values for the standard enthalpy and Gibbs energy changes for reactions 1 and 2: 2(+)(g) + 1H(g) reversible arrow 2H(g) + 1(+)(g) Delta H degrees(1), Delta G degrees(1) 2(+)(g) + 1X(g) reversible arrow 2X(g) + 1(+)(g) Delta H degrees(2), Delta G degrees(2) where X = Cl. This information was used to determine a value of 162.0 +/- 2 .0 kcal mol(-1) for the standard molar enthalpy of formation of gaseous 1(), Delta(f)H degrees(m)(1+,g).