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

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Abstract

The standard molar enthalpies of formation Δf H°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 ΔgcrH°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 Δ1crH°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 ΔfH°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 (HS) of 46.1, 114.7, 8.1, and 5.0 kJ · mol−1, respectively.

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