Online 1H NMR Spectroscopic Study of the Reaction Kinetics in Mixtures of Acetaldehyde and Water Using a New Microreactor Probe Head

Mixtures of acetaldehyde and water are reactive multicomponent systems because poly(oxymethylmethylene) glycols are formed. A study on the kinetics of the formation of these oligomers was carried out using a new microreactor NMR probe head that combines online flow 1H NMR spectroscopy with microreaction technology. The study covers temperatures between 278 and 298 K and pH values between 3.5 and 10.3. From the peak areas in the 1H NMR spectra, quantitative results for the conversion of acetaldehyde were obtained. On the basis of the new data, a reaction kinetic model was developed and numbers for the kinetic constants of poly(oxymethylmethylene) glycol formation were determined together with a correlation that describes their dependence on the temperature and pH value.