The results of proper orthogonal decomposition analyses on CO 2 number density and vorticity magnitude data from reacting rectangular jet simulations are presented. The resulting proper orthogonal decomposition eigenfunctions are used to develop physical insight of the vortex formations and dynamics of these jets and their related mixing and spreading characteristics. It is seen that different vortex structures are captured in the eigenfunctions and that CO 2 and vorticity eigenfunctions are very similar indicating that vortex-driven mixing dominates in these jets. The eigenvalue spectra associated with these eigenfunctions are used to evaluate the information content of the eigenfunctions and the potential for reduced-order models. Using subsets of eigenfunctions with high information content, CO 2 and vorticity magnitude distributions can be represented with relatively few eigenfunctions. However, as the flows develop downstream, more eigenfunctions are needed to represent them to the same level of accuracy. The potential for reduced-order modeling of each field is approximately the same for the jets of aspect ratios 1, 2, and 3; however, there is stronger potential for reduced-order modeling of the CO 2 field than of the vorticity field