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Difluoromethane

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Difluoromethane
Difluoromethane-2D-skeletal
Difluoromethane-2D-skeletal
Spacefill model of difluoromethane
Spacefill model of difluoromethane
Names
Preferred IUPAC name
Difluoromethane[1]
Other names
'R-32

Methylene difluoride
Methylene fluoride

Freon-32
Identifiers
3D model (JSmol)
Abbreviations HFC-32

R-32
FC-32

1730795
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.000.764 Edit this at Wikidata
EC Number
  • 200-839-4
259463
MeSH Difluoromethane
RTECS number
  • PA8537500
UNII
UN number 3252
  • InChI=1S/CH2F2/c2-1-3/h1H2 checkY
    Key: RWRIWBAIICGTTQ-UHFFFAOYSA-N checkY
  • InChI=1/CH2F2/c2-1-3/h1H2
    Key: RWRIWBAIICGTTQ-UHFFFAOYAC
  • FCF
Properties
CH2F2
Molar mass 52.024 g·mol−1
Appearance Colourless gas
Density 1.1 g cm−3(in liquid form)
Melting point −136 °C (−213 °F; 137 K)
Boiling point −52 °C (−62 °F; 221 K)
log P −0.611
Vapor pressure 1,518.92 kPa (220.301 psi) (at 21.1 °C [70.0 °F; 294.2 K])
Hazards
GHS labelling:
GHS02: Flammable
Danger
H220
P210, P377, P381, P403, P410+P403
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineFlammability 4: Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Flash point below 23 °C (73 °F). E.g. propaneInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
1
4
0
648 °C (1,198 °F; 921 K)
Safety data sheet (SDS) MSDS at Oxford University
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)

Difluoromethane, also called HFC-32 is an organofluorine compound with the formula CH2F2. It is a colorless gas that is used as a refrigerant.

Tank of R32 - Difluoromethane

Synthesis

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Difluoromethane is produced by the reaction of dichloromethane and hydrogen fluoride (HF) using SbF5 as a catalyst.[2]

CH2Cl2 + 2 HF → CH2F2 + 2 HCl

Applications

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Difluoromethane is used as refrigerant that has prominent heat transfer and pressure drop performance, both in condensation and vaporization.[3]

Difluoromethane is currently used by itself in residential and commercial air-conditioners in Japan, China, and India as a substitute for R-410A. In order to reduce the residual risk associated with its mild flammability, this molecule should be applied in heat transfer equipment with low refrigerant charge such as brazed plate heat exchangers (BPHE), or shell and tube heat exchangers and tube and plate heat exchangers with tube of small diameter.[4] Many applications confirmed that difluoromethane exhibits heat transfer coefficients higher than those of R-410A under the same operating conditions but also higher frictional pressure drops.[4]

Other uses of difluoromethane include its use as aerosol propellant and blowing agent.

Environmental effects

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The global warming potential (GWP) of HFC-32 is estimated at 677 on a 100-year time window.[5] This is far lower than the GWP for HFC refrigerants it is replacing, but remains sufficiently high to spur continued research into using lower-GWP refrigerants.

Difluoromethane is excluded from the list of VOCs supplied in the United States Clean Air Act due to the ODP being zero.[5]

References

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  1. ^ "Difluoromethane - Compound Summary". The PubChem Project. US: National Center of Biotechnological Information.
  2. ^ Siegemund, Günter; Schwertfeger, Werner; Feiring, Andrew; Smart, Bruce; Behr, Fred; Vogel, Herward; McKusick, Blaine (2000). "Fluorine Compounds, Organic". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a11_349. ISBN 978-3-527-30385-4.
  3. ^ Longo, Giovanni A.; Mancin, Simone; Righetti, Giulia; Zilio, Claudio (2015). "HFC32 vaporisation inside a Brazed Plate Heat Exchanger (BPHE): Experimental measurements and IR thermography analysis". International Journal of Refrigeration. 57: 77–86. doi:10.1016/j.ijrefrig.2015.04.017.
  4. ^ a b Longo, Giovanni A.; Mancin, Simone; Righetti, Giulia; Zilio, Claudio (2016). "HFC32 and HFC410A flow boiling inside a 4 mm horizontal smooth tube". International Journal of Refrigeration. 61: 12–22. doi:10.1016/j.ijrefrig.2015.09.002.
  5. ^ a b Rusch, George M. (2018). "The development of environmentally acceptable fluorocarbons". Critical Reviews in Toxicology. 48 (8): 615–665. doi:10.1080/10408444.2018.1504276. PMID 30474464.

See also

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