Thermochemistry of Alcohols: Experimental Standard Molar Enthalpies of Formation and Strain of Some Alkyl and Phenyl Congested Alcohols

The standard molar enthalpies of formation _fH_m^°(cr) at the temperature T = 298.15 K were determined using combustion calorimetry for di-tert-butyl-methanol (A), di-tert-butyl-iso-propyl-methanol (B), and di-phenyl-methyl-methanol (C). The standard molar enthalpies of sublimation _cr⁸H_m^° of these compounds and of di-phenyl-methanol (D) were obtained from the temperature variation of the vapor pressure measured in a flow system. Molar enthalpies of fusion _cr¹H_m^° of the compounds A–D and of tri-phenyl-methanol (E) were measured by differential scanning calorimeter (DSC). From these data and data available from the literature, the following standard molar enthalpies of formation in gaseous phase _fH_m^°(g) for A, (–397.0 ± 1.2); B, (–418.1 ± 2.3); C, (–34.2 ± 1.3); and D, (0.9 ± 2.1) kJ · mol^–1 were derived, which correspond to strain enthalpies (H_S) of 46.1, 114.7, 8.1, and 5.0 kJ · mol^–1, respectively.