Calorimetric and FTIR Spectrometric Investigation of a Grignard Reaction

Calorimetric and in situ Fourier Transform Infrared (FTIR) spectroscopic studies to monitor the unpredictable initiation of a strongly exothermic Grignard reaction and to determine their thermokinetic parameters are represented. Instead of operating under reflux conditions which are commonly used to control the Grignard formation, the calorimetric measurements were carried out in a closed jacketed stainless steel pressure reactor. This novel technique has some advantages. For example, a more accurate determination of the molar reaction enthalpy is possible, the increase of the reactor temperature and pressure can also be used to monitor the initiation process of the Grignard formation, and the dosage of the pure organic halide into a closed reactor vessel leads to a predictable and reproducible induction time. Thus, this technique might contribute to reduce the hazardous potentials of Grignard reactions.