difluoromethane
{{Chembox
| data page pagename = none
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 442662929
| ImageFileL1 = Difluoromethane-2D-skeletal.png
| ImageFileL1_Ref = {{chemboximage|correct|??}}
| ImageNameL1 = Difluoromethane-2D-skeletal
| ImageFileR1 = Difluoromethane-3D-vdW.png
| ImageFileR1_Ref = {{chemboximage|correct|??}}
| ImageNameR1 = Spacefill model of difluoromethane
| OtherNames = 'R-32
Methylene difluoride
Methylene fluoride
Freon-32
|Section1={{Chembox Identifiers
| Abbreviations = HFC-32
R-32
FC-32
| CASNo = 75-10-5
| CASNo_Ref = {{cascite|correct|CAS}}
| UNII_Ref = {{fdacite|changed|FDA}}
| UNII = 77JW9K722X
| PubChem = 6345
| ChemSpiderID = 6105
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| EINECS = 200-839-4
| UNNumber = 3252
| MeSHName = Difluoromethane
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 47855
| ChEMBL = 115186
| ChEMBL_Ref = {{ebicite|correct|EBI}}
| RTECS = PA8537500
| Beilstein = 1730795
| Gmelin = 259463
| SMILES = FCF
| StdInChI = 1S/CH2F2/c2-1-3/h1H2
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| InChI = 1/CH2F2/c2-1-3/h1H2
| StdInChIKey = RWRIWBAIICGTTQ-UHFFFAOYSA-N
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| InChIKey = RWRIWBAIICGTTQ-UHFFFAOYAC
}}
|Section2={{Chembox Properties
| C=1 | H=2 | F=2
| Appearance = Colourless gas
| Density = 1.1 g cm−3(in liquid form)
| MeltingPtC = −136
| BoilingPtC = −52
| LogP = −0.611
| VaporPressure = {{cvt|1518.92|kPa|psi}} (at {{convert|21.1|°C|F K|disp=sqbr}})
}}
|Section3={{Chembox Hazards
| ExternalSDS = [http://ptcl.chem.ox.ac.uk/MSDS/DI/difluoromethane.html MSDS at Oxford University]
| GHSPictograms = {{GHS02}}
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|220}}
| PPhrases = {{P-phrases|210|377|381|403|410+403}}
| NFPA-H = 1
| NFPA-F = 4
| NFPA-R = 0
| AutoignitionPtC = 648
| AutoignitionPt_notes =
}}
}}
Difluoromethane, also called HFC-32 is an organofluorine compound with the formula CH2F2. It is a colorless gas that is used as a refrigerant.
Synthesis
Difluoromethane is produced by the reaction of dichloromethane and hydrogen fluoride (HF) using SbF5 as a catalyst.{{Cite book|doi=10.1002/14356007.a11_349 |chapter=Fluorine Compounds, Organic |title=Ullmann's Encyclopedia of Industrial Chemistry |date=2000 |last1=Siegemund |first1=Günter |last2=Schwertfeger |first2=Werner |last3=Feiring |first3=Andrew |last4=Smart |first4=Bruce |last5=Behr |first5=Fred |last6=Vogel |first6=Herward |last7=McKusick |first7=Blaine |isbn=978-3-527-30385-4 }}
:{{chem2|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.{{Cite journal |doi = 10.1016/j.ijrefrig.2015.04.017|title = HFC32 vaporisation inside a Brazed Plate Heat Exchanger (BPHE): Experimental measurements and IR thermography analysis|journal = International Journal of Refrigeration|volume = 57|pages = 77–86|year = 2015|last1 = Longo|first1 = Giovanni A.|last2 = Mancin|first2 = Simone|last3 = Righetti|first3 = Giulia|last4 = Zilio|first4 = Claudio}}
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.{{Cite journal |doi = 10.1016/j.ijrefrig.2015.09.002|title = HFC32 and HFC410A flow boiling inside a 4 mm horizontal smooth tube|journal = International Journal of Refrigeration|volume = 61|pages = 12–22|year = 2016|last1 = Longo|first1 = Giovanni A.|last2 = Mancin|first2 = Simone|last3 = Righetti|first3 = Giulia|last4 = Zilio|first4 = Claudio}}
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.
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.{{cite journal|doi=10.1080/10408444.2018.1504276 |title=The development of environmentally acceptable fluorocarbons |date=2018 |last1=Rusch |first1=George M. |journal=Critical Reviews in Toxicology |volume=48 |issue=8 |pages=615–665 |pmid=30474464 }} 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.
References
{{Reflist}}
== See also ==
- R-410A, a refrigerant that is being phased out, and which R-32 is a popular replacement for
- R-454B, another R-410A replacement
- List of refrigerants
External links
- [http://www.fire.nist.gov/bfrlpubs/fire99/art047.html Flammability Measurements of Difluoromethane in Air at 100 °C] {{Webarchive|url=https://web.archive.org/web/20160920232053/http://www.fire.nist.gov/bfrlpubs/fire99/art047.html |date=2016-09-20 }}
- [http://encyclopedia.airliquide.com/encyclopedia.asp?GasID=108 Difluoromethane at Gas Encyclopaedia] {{Webarchive|url=https://web.archive.org/web/20160303180448/http://encyclopedia.airliquide.com/encyclopedia.asp?GasID=108 |date=2016-03-03 }}
- [https://www.nist.gov/kinetics/spectra/ir_spectra/CH2F2%20(HFC-32).pdf IR absorption spectra] {{Webarchive|url=https://web.archive.org/web/20061013150032/http://www.nist.gov/kinetics/spectra/ir_spectra/CH2F2%20(HFC-32).pdf |date=2006-10-13 }}
- [https://www.airgas.com/msds/001054.pdf SDS Data sheet]
{{Halomethanes}}
{{fluorine compounds}}
{{Authority control}}