For societal reasons, it is important to know how a chemical released into the environment will be distributed between the air, water, soil and biota (living things). The properties needed to make such predictions for any chemical are its vapor pressure, its infinite dilution activity coefficient in water (or their product, the Henry's law constant), and its octanol-water partition coefficient. We will briefly discuss the role of each of these properties. Then knowing only the atomic connectivity in a molecule, we show how computational chemistry methods can be used to predict thermodynamic properties of environmental interest when little or no experimental data are available.