Chlorodifluoromethane

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Chlorodifluoromethane

Chlorodifluoromethane or difluoromonochloromethane is a hydrochlorofluorocarbon (HCFC). It is better known under its code names of HCFC-22, R-22, Genetron 22 or Freon 22, and is commonly used in air conditioning

Air conditioning

An air conditioner is an appliance, system, or Mechanism designed to extract heat from an area via a refrigeration cycle. In construction, a complete system of heating, Ventilation , and air conditioning is referred to as "HVAC." Its purpose, in a building or an automobile, is to provide comfort during either hot or cold...
applications, such as residential split systems in the US, rooftop units and window air conditioners. It will soon be phased out due to ozone depletion potential

Ozone depletion potential

The ozone depletion potential of a chemical compound is the relative amount of degradation to the ozone layer it can cause, with trichlorofluoromethane being fixed at an ODP of 1.0....
and status as a potent greenhouse gas

Greenhouse gas

Greenhouse gases are gases in an atmosphere that Absorption and Emission radiation within the Infrared#Different regions in the infrared range....
.

It is an intermediate in the synthesis of tetrafluoroethylene

Tetrafluoroethylene

Tetrafluoroethylene is a chemical compound with the formula C2F4. It is the simplest unsaturated compound fluorocarbon. This gaseous species is used primarily in the industrial preparation of polymers....
, into which it is converted by pyrolysis

Pyrolysis

Pyrolysis is the chemical decomposition of a condensed substance by heating. The word is coined from the Greek language-derived morphemes pyro "fire" and lysys "decomposition"....
.

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Encyclopedia

Air conditioning

Ozone depletion potential

Greenhouse gas

Tetrafluoroethylene

Pyrolysis

Pyrolysis is the chemical decomposition of a condensed substance by heating. The word is coined from the Greek language-derived morphemes pyro "fire" and lysys "decomposition"....
. Difluorocarbene is an intermediate in this reaction. The compound also yields difluorocarbene upon treatment with strong base and is used in the laboratory as a source of this reactive intermediate.

Environmental effects and phase-out

Chlorodifluoromethane was used as an alternative to the highly ozone-depleting CFC-11 and CFC-12, because of its relatively low ozone depletion potential

Ozone depletion potential

Chlorine

Chlorine...
-containing haloalkane

Haloalkane

The haloalkanes are a group of chemical compounds, consisting of alkanes, such as methane or ethane, with one or more halogens linked, such as chlorine or fluorine, making them a type of organic halide....
s. However, even this lower ozone depletion potential is no longer considered acceptable. It will be phased out soon under the Montreal Protocol

Montreal Protocol

The Montreal Protocol on Substances That Deplete the Ozone Layer is an international treaty designed to protect the ozone layer by phasing out the production of a number of substances believed to be responsible for ozone depletion....
, to be replaced by refrigerants with zero ozone depletion potential

Ozone depletion potential

Propane

Propane is a three-carbon alkane, normally a gas, but compressible to a transportable liquid. It is derived from other petroleum products during oil or natural gas processing....
(R-290), and other refrigerants (even though they don't have very similar properties): R-410A

R-410A

R-410A, sold under the trademarked names Puron, Genetron R410A, and AZ-20, is a near-azeotrope mixture of difluoromethane and pentafluoroethane which is used as a refrigerant in air conditioning applications....
(an azeotropic

Azeotrope

An azeotrope is a mixture of two or more liquids in such a ratio that its composition cannot be changed by simple distillation. This occurs because, when an azeotrope is boiled, the resulting vapor has the same ratio of constituents as the original mixture....
mixture of difluoromethane

Difluoromethane

Difluoromethane, also called HFC-32 or R-32, is an organic compound of the Haloalkane variety. It is based on methane, except that two of the four hydrogen atoms have been replaced by fluorine atoms....
and pentafluoroethane

Pentafluoroethane

Pentafluoroethane, also called 1,1,1,2,2-pentafluoroethane, HFC-125, or R-125, is a refrigerant that has zero ozone depletion potential....
), R-507A, R-134a (1,1,1,2-tetrafluroethane) and R-409A.

An additional environmental concern regarding chlorodifluoromethane, as well as some of the proposed replacements, is their global warming potential

Global warming potential

Global warming potential is a measure of how much a given mass of greenhouse gas is estimated to contribute to global warming. It is a relative scale which compares the gas in question to that of the same mass of carbon dioxide ....
. The global warming potential of chlorodifluoromethane is 1700 (1700 times that of carbon dioxide). HFCs such as R-410A have high global warming potential, whereas that of propane (R-290) is only 3.

The US EPA

United States Environmental Protection Agency

The U.S. Environmental Protection Agency is an List of United States federal agencies of the federal government of the United States charged to Regulation of chemicals and protect human health by safeguarding the natural environment: air, water, and land....
has enacted regulation which will phase out the use of HCFC-22 in the near future. Air conditioning manufacturers will no longer be allowed to sell R22 equipment as of January 1, 2010. In the aftermarket service business, the allocation rights for producers who manufacture R22 will be cut each year making the remaining R22 supply potentially smaller than the service demand for the product. This could make R22 scarce in the future, and drive prices to consumers higher.

Physical Properties

Property	Value
Density Density The density of a material is defined as its mass per unit volume. The symbol of density is .... at -69 °C (liquid)	1.49 g.cm^-3
Density Density The density of a material is defined as its mass per unit volume. The symbol of density is .... at -41 °C (liquid)	1.413 g.cm^-3
Density Density The density of a material is defined as its mass per unit volume. The symbol of density is .... at -41 °C (gas)	4.706 kg.m^-3
Density Density The density of a material is defined as its mass per unit volume. The symbol of density is .... at 15 °C (gas)	3.66 kg.m^-3
Specific gravity at 21 °C (gas)	3.08 (air AIR Air is the part of Earth's atmosphere that humans breath and as such Air .Air may also refer to:... = 1)
Specific volume Specific volume Specific volume is the volume occupied by a unit of mass of a material. It is equal to the inverse of density. Specific volume may be expressed in , or .... at 21 °C (gas)	0.275 m³.kg^-1
Density Density The density of a material is defined as its mass per unit volume. The symbol of density is .... at 15 °C (gas)	3.66 kg.m^-3
Triple point Triple point In thermodynamics, the triple point of a substance is the temperature and pressure at which three Phase of that substance coexist in thermodynamic equilibrium.... temperature (T_t)	-157.39 °C (115.76 K)
Critical temperature Critical temperature The critical temperature, Tc, of a material is the temperature above which distinct liquid and gas phases of matter do not exist. As the critical temperature is approached, the properties of the gas and liquid phases become the same resulting in only one phase: the supercritical fluid.... (T_c)	96.2 °C (369.3 K)
Critical pressure (p_c)	4.936 MPa (49.36 bar)
Critical density (?_c)	6.1 mol.l^-1
Latent heat of vaporization (l_v) at boiling point (-40.7 °C)	233.95 kJ.kg^-1
Heat capacity Specific heat capacity Specific heat capacity, also known simply as specific heat, is the measure of the energy required to increase the temperature of a of a substance by a certain Celsius#Temperatures_and_intervals.... at constant pressure (C_p) at 30 °C (86 °F)	0.057 kJ.mol^-1.K^-1
Heat capacity Specific heat capacity Specific heat capacity, also known simply as specific heat, is the measure of the energy required to increase the temperature of a of a substance by a certain Celsius#Temperatures_and_intervals.... at constant volume (C_v) at 30 °C (86 °F)	0.048 kJ.mol^-1.K^-1
Heat capacity ratio Heat capacity ratio The heat capacity ratio or adiabatic index or ratio of specific heats, is the ratio of the heat capacity at constant pressure to heat capacity at constant volume .... at 30 °C (86 °F)	1.178253
Compressibility factor Compressibility factor The compressibility factor is a useful thermodynamic property for modifying the ideal gas law to account for the real gas behaviour. In general, deviations from ideal behavior become more significant the closer a gas is to a phase change, the lower the temperature or the larger the pressure.... (Z) at 15 °C	0.9831
Acentric factor Acentric factor In thermodynamics, the accentric factor is a factor originally used by K.S. Pitzer and coworkers as an expression in an equation for the compressibility factor....	0.22082
Dipole moment Dipole moment Dipole moment refers to the quality of a system to behave like a dipole. Dipole moment is the measured polarity of a polar covalent bond. It is defined as the product magnitude of charge on the atoms and the distance between the two bonded atoms....	1.458 D
Viscosity Viscosity Viscosity is a measure of the Drag of a fluid which is being deformed by either shear stress or extensional stress. In everyday terms , viscosity is "thickness".... at 0 °C	12.56 µPa.s (0.1256 cP)
Ozone depletion potential Ozone depletion potential The ozone depletion potential of a chemical compound is the relative amount of degradation to the ozone layer it can cause, with trichlorofluoromethane being fixed at an ODP of 1.0.... (ODP)	0.055 (CCl₃F Trichlorofluoromethane Trichlorofluoromethane, also called freon-11, CFC-11, or R-11, is a chlorofluorocarbon. It is a colorless, nearly odorless liquid that boils at about room temperature.... = 1)
Global warming potential Global warming potential Global warming potential is a measure of how much a given mass of greenhouse gas is estimated to contribute to global warming. It is a relative scale which compares the gas in question to that of the same mass of carbon dioxide .... (GWP)	1700 (CO₂ Carbon dioxide Carbon dioxide is a chemical compound composed of two oxygen atoms covalent bond to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state.... = 1)

It has two allotropes: crystaline II below 59 K and crystaline I above 59 K to 115.73 K.

External links

IARC Summaries & Evaluations: , ,