Chemical Safety Note: Explosion Hazard during the Distillation of Propargyl Thiocyanate

Abstract

This study is based on the efforts to understand the cause of a laboratory accident at a university in Germany. An explosion occurred during the distillation of propargyl thiocyanate(1), a well-known compound. It is assumed, that an unwanted [3,3]-sigmatropic rearrangment under thermal conditions led to the accumulation of highly reactive isothiocyanatopropa-1,2-diene (2), which actually was the explosive substance. To assess the hazard potential of the established purification procedure, pure 1 was analyzed by DTA and 2 by isothermal reaction calorimetry. The results support our hypothesis of unintended formation of dangerous 2, and safety advice is given to prevent future incidents.

Real Multicomponent Reactions: Synthesis of Highly Substituted 2‐Aminothiazoles

“…The temperature limitation due to the polymerization tendency of allene 2a does not allow working significantly above room temperature. Below this, the yield of unwanted side product 7 increases (Table , Entries 2 and 3).…”

“…Warning: Synthesis and handling of neat allenyl isothiocyanates carry the risk of highly exothermic and vigorous polymerization . Measures of precaution must always be taken .…”