Standard Sublimation Enthalpies of some dichlorophenoxy acids and their methyl esters

The standard sublimation enthalpies of 2,4-dichlorophenoxy acetic acid, 2,4-dichlorophenoxy propionic acid, and 2,4-dichlorophenoxy butyric acid and their methyl esters 2,4-dichlorophenoxy acetic methyl ester and 2,4-dichlorophenoxy butyric methyl ester were determined by direct differential scanning calorimetry (DSC) measurements along with the Langmuir and torsion effusion methods. For 2,4- dichlorophenoxy acetic acid, 2,4-dichlorophenoxy propionic acid, and 2,4-dichlorophenoxy butyric acid, the values ∆subH°(298 K) ) {(122 ( 5), (127 ( 8), and (137 ( 10)} kJ‚mol-1, respectively, were selected. For 2,4-dichlorophenoxy acetic acid methyl ester and 2,4-dichlorophenoxy butyric acid methyl ester, the ∆subH°(298 K) final values 89 kJ‚mol-1 and 100 kJ‚mol-1, respectively, were selected with an estimated error of (10 kJ‚mol-1. From torsion data, the standard sublimation entropies for 2,4-dichlorophenoxy acetic acid, 2,4-dichlorophenoxy propionic acid, and 2,4-dichlorophenoxy butyric acid equal to ∆subS°(298 K) ) (239, 263, and 294) J‚K-1‚mol-1, respectively, were derived, with an error of (4 J‚K-1‚mol-1 for all compounds.