Thermochemical Properties of Triphenylalkanes and Tetraphenylmethane. Strain in Phenyl Substituted Alkanes

The standard (p° = 0.1 MPa) molar enthalpies of sublimation <EQUATION><EQNDATA>%@mt;sys@%Δ%@sx@%cr%@be@%g%@sxx@%%@mx@%</EQNDATA> </EQUATION>H<INF>m</INF>° at the temperature T = 298.15 K for 1,1,2-triphenylethane, triphenylmethane, 1,1,1-triphenylethane, 1,1,1-triphenylbutane, and tetraphenylmethane were obtained from the temperature function of the vapor pressure measured in a flow system. Standard molar enthalpy of formation Δ<INF>f</INF>H<INF>m</INF>°(cr) at the temperature T = 298.15 K was measured using combustion calorimetry for 1,1,1-triphenylbutane. Enthalpies of fusion of all compounds were measured by differential scanning calorimetry. These experimental results together with the data available from the literature were used for the estimation of strain enthalpies of phenyl substituted alkanes and for the improvement of group-contribution methodology.