Thermal Hazard Evaluation and Safety Considerations for the Use of <i>O</i>-Benzoyl-<i>N</i>-alkyl Hydroxylamines as Synthetic Reagents

Numerous synthetic methods utilize O-benzoyl-N-alkyl hydroxylamines (BzO-NR2) as electrophilic aminating reagents. The need for gram scale quantities of these reagents prompted a detailed reactive chemistry evaluation. This report provides information on the thermal hazards associated with this class of BzO-NR2 reagent. Several of these reagents demonstrated low detected onset temperatures, as determined by differential scanning calorimetry (DSC). The observed detected onset temperature was below the reported operating temperatures for some synthetic methods. Variable scan rate DSC data indicated a high probability of autocatalytic decomposition. These data were modeled by using Advanced Kinetics and Technology Solutions (AKTS) software to predict and confirm autocatalytic behavior. Accelerating rate calorimetry (ARC) was performed to confirm the low thermal onset, high exotherm, and gas generation of the decomposition. Finally, micro reaction calorimetry and analytical methods were used to confirm the initial steps of the decomposition pathway. Taken together, these results indicate that care should be taken in the synthesis, use, transport, and storage of these reagents.