1,1-Difluoroethane

1,1-Difluoroethane

Difluoroethane Difluoroethane Difluoroethane Difluoroethane
Difluoroethane
Names
Preferred IUPAC name 1,1-Difluoroethane
Other names Difluoroethane Freon 152a Ethylidene difluoride Ethylidene fluoride HFC-152a R-152a DFE Tinned Wind
Identifiers
CAS Number	75-37-6 Error creating thumbnail: Y
3D model (JSmol)	Interactive image
ChEMBL	ChEMBL325493 Error creating thumbnail: Y
ChemSpider	6128 Error creating thumbnail: Y
ECHA InfoCard
E number
PubChem CID	6368
RTECS number	KI1410000
UNII	0B1U8K2ME0 Error creating thumbnail: Y
CompTox Dashboard (EPA)	{{#property:P3117}}
InChI InChI=1S/C2H4F2/c1-2(3)4/h2H,1H3 Error creating thumbnail: Y Key: NPNPZTNLOVBDOC-UHFFFAOYSA-N Error creating thumbnail: Y InChI=1/C2H4F2/c1-2(3)4/h2H,1H3 Key: NPNPZTNLOVBDOC-UHFFFAOYAM
SMILES FC(F)C
Properties
Chemical formula	C2H4F2
Molar mass	66.05 g/mol
Density	900 g/L @ 25 °C
Melting point	−117 °C (−179 °F; 156 K)
Boiling point	−24.7 °C (−12.5 °F; 248.5 K)
Critical point (T, P)	113.45 °C
Solubility in water	0.54% @ 0 °C
Vapor pressure	536 kPa (4020 mmHg) @ 21.1 °C 510 kPa (5.1 bar) @ 20 °C
Viscosity	8.87 μPa·s (0.00887 cP) @ 25 °C
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	Extremely flammable
GHS labelling:
Pictograms	GHS02: Flammable
Signal word	Danger
NFPA 704 (fire diamond)	1 4 0
Safety data sheet (SDS)	SDS for 1,1-difluoroethane
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Error creating thumbnail: Y verify (what is Error creating thumbnail: Y☒N ?) Infobox references

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 than other hydrofluorocarbons and a shorter atmospheric lifetime (1.4 years).

Production

1,1-Difluoroethane is a synthetic substance that is produced by the mercury-catalyzed addition of hydrogen fluoride to acetylene:

HCCH + 2 HF → CH₃CHF₂

The intermediate in this process is vinyl fluoride (C₂H₃F), the monomeric precursor to polyvinyl fluoride.

Uses

With a relatively low global warming potential (GWP) index of 124 and favorable thermophysical properties, 1,1-difluoroethane has been proposed as an environmentally friendly alternative to R134a. Despite its flammability, R152a 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.

In addition, 1,1-difluoroethane is also commonly used in gas dusters and numerous other retail aerosol products, particularly those subject to stringent volatile organic compound (VOC) requirements.

The molecular weight of difluoroethane is 66, making it a useful and convenient tool for detecting vacuum leaks in gas chromatography–mass spectrometry (GC-MS) systems. The cheap and freely available gas has a molecular weight and fragmentation pattern (base peak at m/z = 51 in typical EI-MS, major peak at m/z = 65) 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 extremely flammable gas, which decomposes rapidly on heating or burning, producing toxic and irritating fumes, including hydrogen fluoride and carbon monoxide.

In a DuPont study, rats were exposed to up to 25,000 ppm (67,485 mg/m³) 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. Repeated or sufficiently high levels of exposure, particularly purposeful inhalation, can precipitate fatal cardiac arrhythmia.

Abuse

Difluoroethane is an intoxicant with abuse potential. It appears to act primarily through GABA_A and glutamate receptors. Fatalities linked to difluoroethane abuse include actress Skye McCole Bartusiak, singer Aaron Carter and wrestler Mike Bell. Bitterants, added voluntarily to some brands to deter purposeful inhalation, are often not legally required; they do not negate or counteract difluoroethane's intoxicating effects.

Environmental abundance

File:HFC152a concentration.jpg

Growth of HFC-152a in Earth's atmosphere since year 2000.

File:HFC-152a mm.png

HFC-152a 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.

Most production, use, and emissions of HFC-152a have occurred within Earth's more industrialized and populated northern hemisphere following the substance's introduction in the 1990s. Its concentration in the northern troposphere reached an annual average of about 10 parts per trillion by year 2011. The concentration of HFC-152a in the southern troposphere is about 50% lower due to its removal rate (i.e. lifetime) of about 1.5 years being similar in magnitude to the global atmospheric mixing time of one to two years.

See also

• List of refrigerants
• Canned air
• IPCC list of greenhouse gases