Heat Capacities and Thermodynamic Properties of (3,4-Dimethoxyphenyl) Acetonitrile (C₁₀H₁₁NO₂)†

The heat capacities of (3,4-dimethoxyphenyl) acetonitrile were measured by a small sample precision automated adiabatic calorimeter over the temperature range from (78 to 399) K. A melting phase transition was observed in the experimental range. The melting temperature, the molar enthalpy, and entropy of the phase transition were determined to be (336.818 ± 0.005) K, (24.72 ± 0.14) kJ·mol⁻¹, and (73.40 ± 0.40) J·K⁻¹·mol⁻¹. The mole fraction purity of the sample used in the adiabatic calorimetric study was determined to be 0.99602 according to the van’t Hoff equation. The thermodynamic functions, (H_T − H_{298.15 K}) and (S_T − S_{298.15 K}), were calculated. The standard molar energy and enthalpy of combustion have been determined, Δ_cU_m⁰ (C₁₀H₁₁NO₂,s) = −(5297.97 ± 2.45) kJ·mol⁻¹ and Δ_cH_m⁰ (C₁₀H₁₁NO₂, s) = −(5301.07 ± 2.45) kJ·mol⁻¹, by means of a precision oxygen-bomb combustion calorimeter at T = 298.15 K. The standard molar enthalpy of formation has been derived, Δ_fH_m⁰ (C₁₀H₁₁NO₂, s) = −(206.10 ± 3.97) kJ·mol⁻¹.