A static method was used to measure the vapor pressures of crystalline and liquid phases of benzamide, N-methylbenzamide, and N,N-dimethylbenzamide, in the temperature ranges (344.8 to 438.2) K, (322.9 to 388.4) K, and (297.0 to 361.7) K, respectively. The vapor pressures of the crystalline phase of benzamide were also measured using the Knudsen effusion method in the temperature range (324.1 to 344.2) K. From the experimental results, the standard molar Gibbs energies and enthalpies of sublimation and of vaporization, at T ) 298.15 K, and the triple points coordinates (p,T) for the three compounds were derived. The temperatures and molar enthalpies of fusion were also determined using differential scanning calorimetry and were compared with the values derived from the vapor pressure measurements. The results enabled the determination of the hydrogen bond enthalpies in the studied compounds.

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The Knudsen mass-loss effusion technique was used to measure the vapor pressures at different temperatures of the following aminomethoxybenzoic acids: 2-amino-3-methoxybenzoic acid, between (349.12 and 369.18) K; 2-amino-5-methoxybenzoic acid, between (353.13 and 375.17) K; 3-amino-4-methoxybenzoic acid, between (379.67 and 399.18) K; 3-amino-5-methoxybenzoic acid, between (380.16 and 400.18) K; and 4-amino-3-methoxybenzoic acid, between (373.14 and 395.17) K. From the temperature dependences of the vapor pressure of the crystalline compounds, the standard (p o ) 10 5 Pa) molar enthalpies and Gibbs energies of sublimation, at T ) 298.15 K, were derived. The results allowed the estimation of these two thermodynamic properties for two isomers not studied in this works2-amino-6-methoxybenzoic acid and 3-amino-2-methoxybenzoic acid. Differential scanning calorimetry was used to measure the temperature and molar enthalpy of fusion of the studied isomers.

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