Freon is originally a trademark for a compond with the general formula CFxCl4−x or C2FxCl6−x. Nowadays, freons are more widely described as substituted hydrocarbons, where a number, or all, hydrogen atoms are exchanged for fluorine, chlorine or more seldom bromine. Two examples from this large family are shown below:

The freon gases are used as refrigerants and therefore often abbreviated as R-11, R-40, aso. Another usage is as propellants in medical inhalants. Normally freons are inert at room temperature and they are more or less nontoxic for human beings. At a hot surface, >250 °C, they might decompose to give toxic and corrosive HF(g) or other unpleasant gases. An IR spectrum of a freon always shows strong C-F peaks.


The inertness of the freon gases creates a problem, as they survive in the environment for a long time, eventually diffusing into the stratosphere (altitudes of 25–40 kilometers) to decompose and simultaneously destroy the UV radiation protective ozone layer. Without this protection, blindness, genetic damage and skin cancers can result for humans and other living creatures.

The freon with highest ozone depleting potential (ODP) is R-11 (CFC-11), trichlorofluoromethane. ODP is a measure of stratospheric ozone destroyed by a chemical relative to the amount destroyed by R-11. Besides freons there are other chemicals with high ODP, for example dinitrogen oxide and fire extinguishers such as halons.

IR spectrum of freon

The IR spectra of various freon gases are rather complex. There are a number of peaks from stretching, rocking or deformation. The strongest C-F absorption peaks are often found at 1100 cm-1, corresponding to about 9.1 µm, which is shown below for CHF2CF3.