Vapor pressures and standar molar sublimation enthalpies of three 6-methylthio-2,4-di(alkylamino)-1,3,5-Triazine Derivatives: Simetryn, Ametryn and Terbutryn.

The standard sublimation enthalpies of simetryn (N,N′-diethyl-6-(methylthio)-2,4-diamine-1,3,5-triazine), ametryn (N-ethyl-N′-(1-methylethyl)-6-(methylthio)-2,4-diamine-1,3,5-triazine), and terbutryn (N-(1,1-dimethylethyl)-N′- ethyl-6-(methylthio)-2,4-diamine-1,3,5-triazine) were determined by nonisothermal differential scanning calorimetry and nonisothermal and isothermal thermogravimetry, both techniques based on the Langmuir equation. For simetryn, ametryn, and terbutryn, the sublimation enthalpy values ∆subH°(298 K) ) {(117 ( 5), (121 ( 5), and (112 ( 5)} kJ‚mol-1, respectively, were selected from nonisothermal and isothermal thermogravimetry data. The temperature dependence of the vapor pressures was selected from isothermal thermogravimetry data for the examined compounds: ln(p/kPa) ) (23.86 ( 0.38) - (10410 ( 160)/(T/K) (from (391.4 to 456.0) K), ln (p/kPa) ) (23.30 ( 0.44) - (10458 ( 189)/(T/K) (from (400.1 to 470.6) K), and ln(p/kPa) ) (21.80 ( 0.41) - (9978 ( 178)/ (T/K) (from (402.8 to 464.3) K) for liquid simetryn, ametryn, and terbutryn, respectively. From the isothermal thermogravimetry data, the standard sublimation entropies for simetryn, ametryn, and terbutryn equal to ∆subS°- (298 K) ) {(243), (244), and (214)} J‚K‚mol-1, respectively, were derived with an estimated uncertainty of ( 10 J‚K-1‚mol-1 for all the studied triazines.