1,1-Difluoroethane


1,1-Difluoroethane, or DFE, is an organofluorine compound with the chemical formula CHF. This colorless gas is used as a refrigerant, where it is often listed as R-152a or HFC-152a. It is also used as a propellant for aerosol sprays and in gas duster products. As an alternative to chlorofluorocarbons, it has an ozone depletion potential of zero, a lower global warming potential and a shorter atmospheric lifetime.

Production

1,1-Difluoroethane is produced by the mercury-catalyzed addition of hydrogen fluoride to acetylene:
The intermediate in this process is vinyl fluoride, the monomeric precursor to polyvinyl fluoride.

Uses

With a relatively low global warming potential index of 124 and favorable thermophysical properties, 1,1-difluoroethane has been proposed as an environmentally friendly alternative to R134a. Despite its flammability, it also presents operating pressures and volumetric cooling capacity similar to R134a so it can be used in large chillers or in more particular applications like heat pipe finned heat exchangers.
Furthermore, 1,1-difluoroethane is also commonly used in gas dusters and many consumer aerosol products, especially those subject to stringent volatile organic compound requirements.
The molecular weight of difluoroethane is 66, making it a useful and convenient tool for detecting vacuum leaks in GC-MS systems. The cheap and freely available gas has a molecular weight and fragmentation pattern distinct from anything in air. If mass peaks corresponding to 1,1-difluoroethane are observed immediately after spraying a suspect leak point, leaks may be identified.

Safety

Difluoroethane is an intoxicant and precipitates fatal cardiac arrhythmia. Several reports of fatal car crashes have been linked to drivers huffing 1,1-difluoroethane. Actress Skye McCole Bartusiak died due to combined effects of difluoroethane and other drugs. Because of inhalant abuse, a bitterant is added to some brands; however even this measure is not legally required and has not prevented widespread use of this product as a drug.
In a DuPont study, rats were exposed to up to 25,000 ppm for six hours daily, five days a week for two years. This has become the no-observed-adverse-effect level for this substance. Prolonged exposure to 1,1-difluoroethane has been linked in humans to the development of coronary disease and angina.