Reactive flash is commonly used as a toy model for understanding the dynamics of industrial reactive distillation processes. Reactive distillation can display complex bifurcation phenomena, including multiplicities and Hopf oscillations. In principle, the simplicity of reactive flash might provide important insights for the design, operation and control of reactive distillation processes. Recent studies have shown that steady state multiplicity and Hopf phenomena can be present even in reactive flash, and such bifurcations are the product of the interaction of the vapor-liquid separation with the chemical transformation. This work uses a simple reactive flash model to show that reactive flash can display singular dynamics represented by spontaneous transitions from one-phase (liquid) to two-phase (liquid-phase) operating modes. Different steady state operating scenarios are described, including a globally stable flashing to unfeasible operation leading to emptiness of the liquid phase. The results are discussed in terms of potential implications for the operation and control of reactive distillation columns. (C) 2013 Elsevier By. All rights reserved.