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.