A reaction-diffusion-convection (RDC) model is introduced as a convenient framework for studying instability scenarios by which chemical oscillators are driven to chaos. Distinct bifurcations in the oscillating patterns are found as diffusion coefficients or Grashof numbers are varied. Singularly there emerge peculiar bifurcation paths in which quasi-periodicity transmutes into a period-doubling sequence to chemical chaos. The opposite influence exhibited by the two parameters in these transitions clearly indicate that diffusion and natural convection are in 'competition' for the stability of ordered dynamics: the former has a stabilizing effect while the latter exerts a destabilizing role. (C) 2011 Elsevier B.V. All rights reserved.