Question

How do the type of bonding and functional groups of Hydroflourocarbons (HFCs) and Dioxins affect their reactivity, and how do the properties of these chemicals (water solubility, vapor pressure, etc.) determine their migration through the environment?

Answer 1

Hydrofluorocarbons (HFCs) are organic compounds that contain fluorine and hydrogen atoms, and are the most common type of organofluorine compounds. Fluorocarbons with few C–F bonds behave similarly to the parent hydrocarbons, but their reactivity can be altered significantly. For example, both uracil and 5-fluorouracil are colourless, high-melting crystalline solids, but the latter is a potent anti-cancer drug. The use of the C-F bond in pharmaceuticals is predicated on this altered reactivity. Several drugs and agrochemicals contain only one fluorine center or one trifluoromethyl group.

Water vapor and clouds provide much of the atmospheric greenhouse heating in today’s atmosphere but are “highly active components of the climate system that respond rapidly to changes in temperature and air pressure by evaporating, condensing, and precipitating”.  Water vapor and clouds are different from other greenhouse gases in that they respond to the physical atmospheric conditions set by other chemicals. As a result, water vapor and clouds supply important feedbacks to climate conditions set by greenhouse gasses and other processes (e.g., orbital variations), rather than being the primary drivers of climate change.

Dioxin, also called polychlorinated dibenzodioxin, any of a group of aromatic hydrocarboncompounds known to be environmental pollutants that are generated as undesirable by-products in the manufacture of herbicides, disinfectants, and other agents.The family of dioxins is characterized chemically by the presence of two benzene rings connected by a pair of oxygen atoms. Each of the eight carbon atoms on the rings that are not bonded to oxygen can bind with hydrogen atoms or atoms of other elements. By convention these positions are assigned the numbers 1 through 4 and 6 through 9. The more toxic dioxins carry chlorine atoms at these positions, and the best-known one has chlorine atoms at the 2,3,7, and 8 positions.