The standard molar enthalpy of the base catalysed hydrolysis of methyl paraben revisited
Abstract The standard molar enthalpy of the base catalysed hydrolysis of methyl paraben, D r H m o was obtained at 298.02 K, 303.04 K and 310.01 K. The determination relied on isothermal microcalorimetry measurements and on a thermochemical scheme that, in contrast with previous strategies, does not require kinetic information. The results obtained were D r H m o (50.99 0.61) kJ*mol 1 at 298.02 K, D r H m o (50.60 0.82) kJ*mol 1 at 303.04 K, and D r H m o (49.64 0.90) kJ*mol 1 at 310.01 K. The D r H m o value at 298 K is in very good agreement with the previously recommended benchmark at this temperature. The current procedure allowed, however, a ~7 fold improvement in precision. It was also found that the D r H m o values show a linear variation with temperature. The fact that this variation is small lends support to the previous assumption of a negligible temperature dependency of D r H m o around 298 K. The present work resolves some important discrepancies in the reported standard molar enthalpies of the base catalysed hydrolysis of methyl paraben. Such inconsistencies can have a considerable impact on the determination of the effective volume of flow through calorimetric apparatus. This parameter is essential to obtain kinetic and thermodynamic information on the growth, metabolism, and adaptation of living cells from flow calorimetry experiments.