General Description
Synonyms: Arcton; Dymel; Freon; Frigen; Genetron; Halon; Isceon; Isotron.
Description: Dichlorodifluoromethane 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. The gas in high concentrations has a faint etherlike odor. Dichlorodifluoromethane is noncorrosive, nonirritating, and nonflammable. Dichlorotetrafluoroethane is a colorless, nonflammable liquefied gas with a faint, ethereal odor. Trichloromonofluoromethane is a clear, volatile liquid at room temperature and atmospheric pressure. It has a characteristic carbon tetrachloride-like odor and is nonirritating and nonflammable.
Chemical Name: Dichlorodifluoromethane
(b)1,2-Dichloro-1,1,2,2-tetrafluoroethane
(c)Trichlorofluoromethane
Uses
Dichlorodifluoromethane, dichlorotetrafluoroethane, and trichloromonofluoromethane are chlorofluorocarbon (CFC) aerosol propellants used in pharmaceutical formulations. They are no longer used in metered-dose inhaler (MDI) formulations, with few exceptions for existing MDIs.
C Chlorofluorocarbons (CFC) 173 Dichlorodifluoromethane is used as an aerosol propellant in MDIs, either as the sole propellant or in combination with dichlorotetrafluoroethane, trichloromonofluoromethane, or mixtures of these chlorofluorocarbons.
Dichlorodifluoromethane may also be used as a propellant in an aerosolized sterile talc used for intrapleural administration and is also used alone in some MDIs containing a steroid.
Dichlorotetrafluoroethane is used in combination with dichlorodifluoromethane, and in several cases with dichlorodifluoromethane and trichloromonofluoromethane, as the propellant in metered-dose oral and nasal aerosols.
Trichloromonofluoromethane is used in combination with dichlorodifluoromethane as the propellant in metered-dose inhaler aerosols.
It is also used in combination with dichlorotetrafluoroethane and dichlorodifluoromethane.
These three propellants have been blended to obtain suitable solubility characteristics for MDIs when formulated as solutions.
They will produce suitable vapor pressures so that optimum particle-size distribution as well as suitable respiratory fractions may be achieved.
Incompatibilities
The presence of greater than 5% water in solutions that contain trichloromonofluoromethane may lead to hydrolysis of the propellant and the formation of traces of hydrochloric acid, which may be irritant to the skin or cause corrosion of metallic canisters. Trichloromonofluoromethane may also react with aluminum, in the presence of ethanol, to cause corrosion within a cylinder with the formation of hydrogen gas. Similarly, alcohols in the presence of trace amounts of oxygen, peroxides, or other free-radical catalysts may react with trichloromonofluoromethane to form trace quantities of hydrochloric acid.
Safety
Dichlorodifluoromethane, dichlorotetrafluoroethane, and trichloromonofluoromethane have been used for over 50 years as propellants in topical, oral, and nasal aerosol formulations, and are generally regarded as nontoxic and nonirritant materials when used as directed.
Handling Precautions
Dichlorodifluoromethane and dichlorotetrafluoroethane are usually encountered as a liquefied gas and appropriate precautions for handling such materials should be taken. Eye protection, gloves, and protective clothing are recommended. These propellants should be handled in a well-ventilated environment. Chlorofluorocarbon vapors are heavier than air and do not support life; therefore, when cleaning large tanks that have contained chlorofluorocarbons, adequate provisions for supply of oxygen in the tanks must be made in order to protect workers cleaning the tanks.