Multiple Species Chemical Modeling as a Structural and Evolutionary Probe of Star-Forming Regions

We present detailed models of the time- and space-dependent gas-phase chemistry for the envelopes of star forming regions. We consider both the hot, high-mass region AFGL 2591 as well as the low-mass region IRAS 16293-2422 which may contain a hot core. The chemical and thermal balance models are used to probe the structure inferred from observational studies (van der Tak, et al. 2000; Schoier, et al. 2002). We compare the resulting model predictions with observations toward these regions which cover a wide range of physical conditions within the source. With this comparison, we study the chemistry, and evolution of the regions.