Abstract :
The imidazole catalysed hydrolysis of triacetin has recently been proposed as a test reaction for isothermal heat conduction microcalorimeters affording validation and traceability for results derived from these instruments. The published values for ΔRH, −91.7+3.0 kJ mol−1 and for the rate constant at 298 K, k, 2.8×10−6±9.7×10−8 dm3 mol−1 s−1, were the results from an international inter- and intra-laboratory study. The protocol for the conduct of the reaction specifies the reaction composition and a temperature of 298 K. Here, we report the temperature and imidazole concentration dependence of the rate constant for this reaction and the derived value of the activation energy; Ea=64.30±2.00 kJ mol−1. The value of ΔRH is independent of temperature and a test for completeness of reaction (i.e. the reaction goes to completion at all temperatures and no effective equilibrium constant is determinable) is described.
