Name: Difluoroethane (HFC)
CAS No: 1,1-Difluoroethane [75-37-6]
None adopted.
Dymel 152a; ethylene fluoride; Genetron 152a; halocarbon 152a; HFC 152a; P-152a; propellant 152a; refrigerant 152a; Solkane 152a.
1,1-Difluoroethane [75-37-6]
C2H4F2 66.05
Difluoroethane, a hydrofluorocarbon (HFC), is an aerosol propellant used in topical pharmaceutical formulations.(1) Difluoroethane may be used as a vehicle for dispersions and emulsions. Since difluoroethane does not contain chlorine, there are no environmental controls on the use of this material as a propellant, since it does not deplete the ozone layer and is not a greenhouse gas.
Difluoroethane is a liquefied gas and exists as a liquid at room temperature when contained under its own vapor pressure, or as a gas when exposed to room temperature and atmospheric pressure. The liquid is practically odorless and colorless. Difluoroethane is noncorrosive and nonirritating.
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Boiling point 24.78C Critical temperature 113.58C Density 0.90 g/cm3 for liquid at 258C; 0.81 g/cm3 for liquid at 54.58C. Flammability Flammable. Limits of flammability 3.7–18.0% v/v in air. Melting point 1178C Solubility Soluble 1 in 357 parts of water at 258C. Surface tension 11.25 mN/m (11.25 dynes/cm) for liquid at 208C. Vapor density (absolute) 2.949 g/m3 at standard temperature and pressure. Vapor density (relative) 2.29 (air = 1) Vapor pressure 600 kPa (61.7 psig) at 21.18C; 1317 kPa (191 psia) at 54.58C. Viscosity (dynamic) 0.243 mPa s (0.243 cP) for liquid at 208C.
Difluoroethane is a nonreactive and stable material. The liquefied gas is stable when used as a propellant and should be stored in a metal cylinder in a cool, dry place.
Compatible with the usual ingredients used in the formulation of pharmaceutical aerosols.
Difluoroethane is prepared from ethyne by the addition of hydrogen fluoride in the presence of a suitable catalyst. The difluoroethane formed is purified to remove all traces of water, as well as traces of the starting materials.
Difluoroethane may be used as an aerosol propellant in topical pharmaceutical formulations. It is generally regarded as an essentially nontoxic and nonirritant material. Deliberate inhalation of excessive quantities of this propellant may result in death, and the following ‘warning’ statements must appear on the label of all aerosols: WARNING: Avoid inhalation. Keep away from eyes or other mucous membranes. (Aerosols designed specifically for oral and nasal inhalation need not contain this statement.) WARNING: Do not inhale directly; deliberate inhalation of contents can cause death. or WARNING: Use only as directed; intentional misuse by deliberately concentrating and inhaling the contents can be harmful or fatal. Additionally, the label should contain the following information: WARNING: Contents under pressure. Do not puncture or incinerate container. Do not expose to heat or store at room temperature above 1208F (498C). Keep out of the reach of children. When propellants are used in topical aerosols they may cause a chilling effect on the skin, although this effect has been somewhat overcome by the use of vapor-tap valves. The propellants quickly vaporize from the skin, and are nonirritating when used as directed.
Difluoroethane is usually encountered as a liquefied gas and appropriate precautions for handling such materials should be taken. Eye protection, gloves, and protective clothing are recommended. Difluoroethane should be handled in a well-ventilated environment. Fluorocarbon vapors are heavier than air and do not support life; therefore, when cleaning large tanks that have contained these propellants, adequate provision for oxygen supply in the tanks must be made in order to protect workers cleaning the tanks. Difluoroethane is flammable; see Section 10. When it is heated to decomposition, toxic fumes of hydrogen fluoride may be formed
Accepted in the USA, by the FDA, for use as a topical aerosol propellant.
Tetrafluoroethane.
Difluoroethane is useful as an aerosol propellant in that it shows greater miscibility with water than some other fluorocarbons. Although not used in new formulations, difluoroethane may still be present in some commercial products. For a discussion of the numerical nomenclature applied to this aerosol propellant, see Chlorofluorocarbons. The PubChem Compound ID (CID) for difluoroethane is 6368