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Chlorofluorocarbons (CFC)


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 ether like odor.
liquefied gas and exists as a liquid at room temperature

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.




(a) Dichlorodifluoromethane (Propellant 12)
(b) Dichlorotetrafluoroethane (Propellant 114)
(c) Trichloromonofluoromethane (Propellant 11)

Nonproprietary Names

(a) USP-NF: Dichlorodifluoromethane
(b) USP-NF: Dichlorotetrafluoroethane
(c) USP-NF: Trichloromonofluoromethane

Synonyms
Arcton; Dymel; Freon; Frigen; Genetron; Halon; Isceon; Isotron.

Chemical Name and CAS Registry Number

(a) Dichlorodifluoromethane [75-71-8]
(b) 1, 2-Dichloro-1, 1, 2, 2-tetrafluoroethane [76-14-2]
(c) Trichlorofluoromethane [75-69-4]

Empirical Formula and Molecular Weight

(a) CCl2F2 120.91
(b) C2Cl2F4 170.92
(c) CCl3F 137.37

Functional Category: Aerosol propellant.

Applications in Pharmaceutical Formulation or Technology

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. 

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.

Blends of trichloromonofluoromethane and dichlorodifluoromethane (propellant 11/12) or propellant 11/114/12 produce vapor pressures of 103–484 kPa (15–70 psig) at 258°C, which adequately cover the range of pressures required to produce the proper particle size distribution for satisfactory aerosol products. Trichloromonofluoromethane is unique among the chlorofluorocarbon propellants in that it is a liquid at room temperature and atmospheric pressure, and can be used to prepare a slurry with insoluble medicinal agents.



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