Trichlorofluoromethane, also called freon-11, CFC-11, or R-11, is a chlorofluorocarbon (CFC). It is a colorless, faintly ethereal, and sweetish-smelling liquid that boils around room temperature.[5] CFC-11 is a Class 1 ozone-depleting substance which damages Earth's protective stratospheric ozone layer.[6]
Historical use
Trichlorofluoromethane was first widely used as a refrigerant. Because of its high boiling point compared to most refrigerants, it can be used in systems with a low operating pressure, making the mechanical design of such systems less demanding than that of higher-pressure refrigerants R-12 or R-22.
Trichlorofluoromethane is used as a reference compound for fluorine-19 NMR studies.
Trichlorofluoromethane was formerly used in the drinking bird novelty, largely because it has a boiling point of 23.77 °C (74.79 °F). The replacement, dichloromethane, boiling point 39.6 °C (103.3 °F), requires a higher ambient temperature to work.
Prior to the knowledge of the ozone depletion potential of chlorine in refrigerants and other possible harmful effects on the environment, trichlorofluoromethane was sometimes used as a cleaning/rinsing agent for low-pressure systems.[7]
Trichlorofluoromethane was included in the production moratorium in the Montreal Protocol of 1987. It is assigned an ozone depletion potential of 1.0, and U.S. production was ended on January 1, 1996.[6]
Regulatory challenges
In 2018, the atmospheric concentration of CFC-11 was noted by researchers to be declining more slowly than expected,[10][11] and it subsequently emerged that it remains in widespread use as a blowing agent for polyurethane foam insulation in the construction industry of China.[12] In 2021, researchers announced that emissions declined by 20,000 U.S. tons from 2018 to 2019, which mostly reversed the previous spike in emissions.[13] In 2022, the European Commission announced an updated regulation that mandates the recovery and prevention of emissions of CFC-11 blowing agents from foam insulation in demolition waste, which is still emitted at significant scale.[14]
CFC-11 measured by the Advanced Global Atmospheric Gases Experiment (AGAGE) in the lower atmosphere (troposphere) at stations around the world. Abundances are given as pollution free monthly mean mole fractions in parts-per-trillion.
Hemispheric and Global mean concentrations of CFC-11 (NOAA/ESRL)
Time-series of atmospheric concentrations of CFC-11 (Walker et al., 2000)
^Touloukian, Y.S., Liley, P.E., and Saxena, S.C. Thermophysical properties of matter - the TPRC data series. Volume 3. Thermal conductivity - nonmetallic liquids and gases. Data book. 1970.
^Banks, A.A.; Emeléus, H.J.; Haszeldine, R. N.; Kerrigan, V. (December 1948). "443. The reaction of bromine trifluoride and iodine pentafluoride with carbon tetrachloride, tetrabromide, and tetraiodide and with tetraiodoethylene". Journal of the Chemical Society: 2188–2190. doi:10.1039/JR9480002188.
