In this article, we present some results for isothermal isobaric reactive separation process problems. We also demonstrate that, even in isothermal isobaric reactive separation processes, which are probably the least nonlinear of all reactive separation processes, we get nonlinear phenomenon such as Hopf bifurcations. While it has been shown that Hopf bifurcations are impossible in isothermal continuous stirred tank reactor (CSTR) problems involving the methyl tert-butyl ether (MTBE) and tert-amyl methyl ether (TAME) reactions, and also in nonreactive flash problems, we demonstrate in this paper that isothermal reactive flash processes involving both MTBE and TAME mixtures exhibit Hopf bifurcations. This shows that instabilities and oscillations can occur even in isothermal reactive separation systems and are not necessarily due to multiple stages. Additionally, we show that the Rachford-Rice procedure can be extended to reactive systems.