Difluoromethane

Difluoromethane, also called HFC-32 or R-32, is an organofluorine compound with the formula CH₂F₂. It is a colorless gas that is used as a refrigerant. As a hydrofluorocarbon, R-32 is being phased out in the EU.^[2]

Difluoromethane

Difluoromethane-2D-skeletal Spacefill model of difluoromethane
Names
Preferred IUPAC name Difluoromethane[1]
Other names 'R-32 Methylene difluoride Methylene fluoride Freon-32
Identifiers
CAS Number	75-10-5 Y
3D model (JSmol)	Interactive image
Abbreviations	HFC-32 R-32 FC-32
Beilstein Reference	1730795
ChEBI	CHEBI:47855 Y
ChEMBL	ChEMBL115186 Y
ChemSpider	6105 Y
ECHA InfoCard	100.000.764
EC Number	200-839-4
Gmelin Reference	259463
MeSH	Difluoromethane
PubChem CID	6345
RTECS number	PA8537500
UNII	77JW9K722X N
UN number	3252
CompTox Dashboard (EPA)	DTXSID6029597
InChI InChI=1S/CH2F2/c2-1-3/h1H2 Y Key: RWRIWBAIICGTTQ-UHFFFAOYSA-N Y InChI=1/CH2F2/c2-1-3/h1H2 Key: RWRIWBAIICGTTQ-UHFFFAOYAC
SMILES FCF
Properties
Chemical formula	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:
Pictograms
Signal word	Danger
Hazard statements	H220
Precautionary statements	P210, P377, P381, P403, P410+P403
NFPA 704 (fire diamond)	1 4 0
Autoignition temperature	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 YN ?) Infobox references

Synthesis

Difluoromethane is produced by the reaction of dichloromethane and hydrogen fluoride (HF) using SbF₅ as a catalyst.^[3]

CH₂Cl₂ + 2 HF → CH₂F₂ + 2 HCl

Applications

Difluoromethane is used as refrigerant that has prominent heat transfer and pressure drop performance, both in condensation and vaporization.^[4]

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.^[5] 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.^[5]

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

Environmental effects

The global warming potential (GWP) of HFC-32 is estimated at 677 on a 100-year time window.^[6] This is far lower than the GWP for HFC refrigerants^[which?] it is replacing, but remains sufficiently high to spur continued research into using lower-GWP refrigerants.

Difluoromethane is excluded from the 1963 list of VOCs restricted by the United States Clean Air Act due to the ODP being zero.^[6]

European Union phase-out

In order to reduce greenhouse gas emissions, the European Union passed a law aiming at phasing out several high-GWP hydrofluorocarbon refrigerants, including R-32. Sale of R-32-based domestic refrigerators are banned from 1 January 2026, and air conditioners and heat pumps from 2027 to 2030, depending on capacity and equipment type. ^[2]

Replacements being considered are:

• R290 AKA Propane, but this is highly flammable and not suitable for many residential installation. Manufacturers are also trying to restrict DIY installations of it, which increases costs.
• R454C, this is a mix of 21.5 percent R-32 and 78.5 percent R1234yf. This is under the 150GWP limit, but has a worse COP Additionally R1234yf can decompose into the highly toxic forever chemical TFA.
• R744 AKA CO2, however engineering challenges remain because the cost is too high for residential use.