Standard molar enthalpies and entropies of vaporization for twolow-melting trichlorophenoxy herbicides

The standard sublimation enthalpies of (2,4,5-trichlorophenoxy)acetonitrile and (2,4,5-trichlorophenoxy)aniline were determined by isothermal thermogravimetry using the Langmuir equation and by non-isothermal differential scanning calorimetry for comparison. The used procedure was previously tested using three reference compounds: benzoic acid, succinic acid and salicylic acid. The results compared to those reported in literature show an excellent agreement for two of the three compounds while the third agrees quite well. For (2,4,5-trichlorophenoxy)acetonitrile and (2,4,5-trichlorophenoxy)aniline, the extrapolation of data at 298.15 K were obtained, respectively: Δ_subH°(298 K)={(106±4) and (101±4)} kJ mol^–1. From Clausius Clapeyron equation obtained after the determination of the vaporization constant α′, the following standard sublimation entropies for (2,4,5-trichlorophenoxy)acetonitrile and (2,4,5-trichlorophenoxy)aniline equal to Δ_subS°(298 K)=(251 and 237) J K^–1 mol^–1, respectively, were derived, with an error of ±4 J K^–1 mol^–1 equal for the studied herbicides.