Influence of deteriorated solvent on induction period of Grignard reagent formation

Abstract

The influence of a degraded solvent on Grignard reagent formation was investigated in terms of heat release behaviour. Since degraded solvent is supposed to contain peroxide by oxidation with air as well as water from atmosphere, peroxide in this study was intentionally produced by the storage of tetrahydrofuran in a pressurized oxygen atmosphere and the induction periods were measured. The induction period which appears prior to the main exothermic reaction increased with increasing amounts of peroxide and water content, respectively. However, there was a difference in heat release behaviour; the reaction including peroxide showed a delay in the heat release and two exothermic peaks, while the solvent that included water simply showed a delay in the start of the reaction. c-Butyrolactone was found to be a product derived from peroxide, by component analysis of the oxidized solvent. c-Butyrolactone caused an induction period when it was added to the solvent. This work suggests a deteriorated solvent can lead to inappropriate handling which cause a runaway reaction and gives insight to the chemical industry that manages the risk of potentially hazardous chemical reactions.

Infrared Spectroscopy as Process Analytics to Identify and Quantify Grignard Reagents

“…This new band stems from γ-butyrolactone, which is formed due to THF hydroperoxide decomposition. Being present in small amounts, it results in a delayed Grignard reagent formation, while at large amounts it can even prevent the formation of the Grignard reagent . Using stabilized THF instead (e.g., by means of added butylated hydroxytoluene) can inhibit the formation of peroxides and prevent a delay and loss in Grignard reagent formation.…”

“…Only few infrared spectra or parts of spectra of Grignard reagents are depicted or described in literature. ,,,− ,, Most of these spectra were obtained from the Grignard reagent in THF or DEE. In addition, several Grignard reagents are mentioned in the literature to be analyzed or identified by infrared spectroscopy, but the spectra were not reported, ,,,, including benzylmagnesium chloride, 5-fluoro-2-methoxyphenylmagnesium bromide, methylmagnesium iodide, 2-thienylmagnesium bromide and vinylmagnesium bromide . In other publications, infrared spectroscopy has been used to follow the formation of Grignard reagents or the Grignard reaction.…”

Crush It Safely: Safety Aspects of Mechanochemical Grignard Synthesis

“…The reaction typically requires some induction periods before an exothermic reaction takes place. The formation of a passive layer of magnesium hydroxide and carbonate and the presence of water and peroxide contaminants in the solvent both contribute to the increased induction period. Numerous attempts have been made to facilitate the Grignard reagent formation, which involves some kind of metal surface activation including the addition of an etching agent such as iodine, 1,2-dibromoethane, or diisobutylaluminum hydride (DIBAL-H) or by using a freshly prepared highly dispersed magnesium powder .…”