1,1-Difluoroethane

1,1-Difluoroethane, or DFE, is an organofluorine compound with the chemical formula C2H4F2. This colorless gas is used as a refrigerant, where it is often listed as R-152a (refrigerant-152a) or HFC-152a (hydrofluorocarbon-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 (124) and a shorter atmospheric lifetime (1.4 years). It has recently been approved for use in automobile applications as an alternative to R-134a. 1,1-Difluoroethane is produced by the mercury-catalyzed addition of hydrogen fluoride to acetylene: The intermediate in this process is vinyl fluoride (C2H3F), the monomeric precursor to polyvinyl fluoride. This molecule, thanks to its relatively low Global Warming Potential (GWP) index equal to 140 and to favorable thermophysical properties, has been proposed as a very promising environmentally friendly alternative to R134a. Despite its flammability, it also presents operating pressures and Volumetric Cooling Capacity (VCC) 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 duster (commonly thought of as 'tinned wind') and many consumer aerosol products, especially those subject to stringent VOC 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 (base peak 51 m/z in typical EI-MS, major peak at 65 m/z) 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. Difluoroethane is an intoxicant if inhaled and is hazardous to health. The low cost, easy availability, and packaging of dusting sprays in a valved aerosol can encourage impulsive use. The practice of deliberately inhaling or “huffing” of the gas can be fatal. Though often overlooked due to lack of identification via common drug screens, it has caused the instantaneous deaths of numerous individuals by precipitating fatal cardiac arrhythmia. Several reports of fatal car crashes have been linked to drivers huffing 1,1-difluoroethane. 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 (67,485 mg m−3) 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.