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Revision as of 12:05, 2 August 2011 editHRoestBot (talk | contribs)53,714 editsm r2.6.5) (robot Adding: tl:Difluoromethane← Previous edit		Latest revision as of 17:30, 21 November 2024 edit undoDpieski (talk | contribs)90 editsm Arranged based on text reference
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	{{Multiple issues|Lead too short = March 2011|No footnotes = March 2011|Technical = March 2011|Trivia = March 2011}}
	{{Chembox		{{Chembox
			| data page pagename = none
			| Verifiedfields = changed
	| Watchedfields = changed		| Watchedfields = changed
	| verifiedrevid = 414423130		| verifiedrevid = 442662929
	| ImageFileL1 = Difluoromethane-2D.svg		| ImageFileL1 = Difluoromethane-2D-skeletal.png
	| ImageFileL1_Ref = {{chemboximage|correct|??}}		| ImageFileL1_Ref = {{chemboximage|correct|??}}
			| ImageNameL1 = Difluoromethane-2D-skeletal
	| ImageSizeL1 = 121
	| ImageNameL1 = Stereo skeletal formula of difluoromethane with all explicit hydrogens added
	| ImageFileR1 = Difluoromethane-3D-vdW.png		| ImageFileR1 = Difluoromethane-3D-vdW.png
	| ImageFileR1_Ref = {{chemboximage|correct|??}}		| ImageFileR1_Ref = {{chemboximage|correct|??}}
			| ImageNameR1 = Spacefill model of difluoromethane
	| ImageSizeR1 = 121
			| PIN = Difluoromethane<ref name="pubchem">{{cite web|title = Difluoromethane - Compound Summary|url = https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=6345&loc=ec_rcs|work = The PubChem Project|location = US|publisher = National Center of Biotechnological Information}}</ref>
	| ImageNameR1 = Spacefill model of difluoromethane
	| SystematicName = Difluoromethane<ref>{{cite web|title = Difluoromethane - Compound Summary|url = http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=6345&loc=ec_rcs|work = The PubChem Project|location = USA|publisher = National Center of Biotechnological Information}}</ref>
	| OtherNames = Carbon fluoride hydride<br />		| OtherNames = Carbon fluoride hydride<br />
	Methylene difluoride<br />		Methylene difluoride<br />
	Methylene fluoride<br />		Methylene fluoride<br />
			Freon-32{{citation needed|date=July 2024}}
	Freon-32
	| Section1 = {{Chembox Identifiers		|Section1={{Chembox Identifiers
	| Abbreviations = HFC-32<br />		| Abbreviations = HFC-32<br />
	R-32<br />		R-32<br />
	FC-32<br />		FC-32
	| CASNo = 75-10-5		| CASNo = 75-10-5
	| CASNo_Ref = {{cascite|correct|CAS}}		| CASNo_Ref = {{cascite|correct|CAS}}
			| UNII_Ref = {{fdacite|changed|FDA}}
	| PubChem = 6345
			| UNII = 77JW9K722X
	| PubChem_Ref = {{Pubchemcite|correct|PubChem}}
	| ChemSpiderID = 6105		| PubChem = 6345
			| ChemSpiderID = 6105
	| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
			| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
	| EINECS = 200-839-4
	| UNNumber = 3252		| EINECS = 200-839-4
	| MeSHName = Difluoromethane		| UNNumber = 3252
			| MeSHName = Difluoromethane
			| ChEBI_Ref = {{ebicite|correct|EBI}}
	| ChEBI = 47855
	| ChEMBL = 115186		| ChEBI = 47855
	| ChEMBL_Ref = {{ebicite|correct|EBI}}		| ChEMBL = 115186
			| ChEMBL_Ref = {{ebicite|correct|EBI}}
	| RTECS = PA8537500		| RTECS = PA8537500
	| Beilstein = 1730795		| Beilstein = 1730795
	| Gmelin = 259463		| Gmelin = 259463
	| SMILES = FCF		| SMILES = FCF
	| StdInChI = 1S/CH2F2/c2-1-3/h1H2		| StdInChI = 1S/CH2F2/c2-1-3/h1H2
	| StdInChI_Ref = {{stdinchicite|correct|chemspider}}		| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
	| InChI = 1/CH2F2/c2-1-3/h1H2		| InChI = 1/CH2F2/c2-1-3/h1H2
	| StdInChIKey = RWRIWBAIICGTTQ-UHFFFAOYSA-N		| StdInChIKey = RWRIWBAIICGTTQ-UHFFFAOYSA-N
	| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}		| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
	| InChIKey = RWRIWBAIICGTTQ-UHFFFAOYAC		| InChIKey = RWRIWBAIICGTTQ-UHFFFAOYAC
	}}		}}
	| Section2 = {{Chembox Properties		|Section2={{Chembox Properties
	| C = 1		| C=1 | H=2 | F=2
			| Appearance = Colourless gas
	| H = 2
			| Density = 1.1 g cm<sup>−3</sup>(in liquid form)
	| F = 2
			| MeltingPtC = −136
	| ExactMass = 52.012456474 g mol<sup>-1</sup>
			| BoilingPtC = −52
	| Appearance = Colorless gas
			| LogP = -0.611
	| Density = 1.1 g cm<sup>-3</sup>
			| VaporPressure = {{cvt|1518.92|kPa|psi}} (at {{convert|21.1|°C|F K|disp=sqbr}})
	| MeltingPtC = −136
	| BoilingPtC = −52
	| LogP = -0.611
	| VaporPressure = 1518.92 kPa (at 21.1 °C)
	}}		}}
	| Section3 = {{Chembox Hazards		|Section3={{Chembox Hazards
	| ExternalMSDS =		| ExternalSDS =
	| EUClass = {{Hazchem F}}		| GHSPictograms = {{GHS02}}
			| GHSSignalWord = Danger
	| RPhrases = {{R11}}
	| SPhrases = {{S9}}, {{S16}}, {{S33}}		| HPhrases = {{H-phrases|220}}
			| PPhrases = {{P-phrases|210|377|381|403|410+403}}
	| NFPA-H = 1
	| NFPA-F = 4		| NFPA-H = 1
	| NFPA-R = 1		| NFPA-F = 4
			| NFPA-R = 0
	| Autoignition = 648 °C
			| AutoignitionPtC = 648
			| AutoignitionPt_notes =
	}}		}}
	}}		}}
			'''Difluoromethane''', also called difluoromethylene, '''HFC-32''' '''Methylene Fluoride''' or '''R-32''', is an ] of the ] variety. Invented in 1964 by Hoechst AG (not Daikin) it has the formula of CH<sub>2</sub>F<sub>2</sub>. It is a colorless gas in the ambient atmosphere and is slightly soluble in water, with a high thermal stability.<ref name=":4">{{Cite journal|date=January 2021|title=Editorial Board|journal=Journal of Fluorine Chemistry|volume=241|pages=109706|doi=10.1016/s0022-1139(20)30404-8|s2cid=243320092|issn=0022-1139|doi-access=free}}</ref>{{Failed verification|date=February 2022}} Due to the low melting and boiling point, ({{convert|-136.0 and -51.6|°C|F K|disp=sqbr}} respectively) contact with this compound may result in frostbite.<ref name=":4" />{{Failed verification|date=February 2022}} In the United States, the ] Section 111 on Volatile Organic Compounds (VOC) has listed difluoromethane as an exception (since 1997) from the definition of VOC due to its low production of tropospheric ozone.<ref name=":12">{{Cite journal|date=August 1993|title=Stratospheric Ozone Protection: The Montreal Protocol and Title VI of the Clean Air Act Amendments of 1990|journal=Air & Waste|volume=43|issue=8|pages=1066–1067|doi=10.1080/1073161x.1993.10467184|issn=1073-161X|doi-access=free}}</ref> Difluoromethane is commonly used in endothermic processes such as refrigeration or air conditioning.
	'''Difluoromethane''', also called '''HFC-32''' or '''R-32''', is an ] of the ] variety. It is based on ], except that two of the four ] atoms have been replaced by ] atoms. Hence the formula is CH<sub>2</sub>F<sub>2</sub> instead of CH<sub>4</sub> for normal methane.
			{{Further|Difluoromethane (data page)}}
			]
	== Physical properties ==
	{| class="wikitable"
	|-
	! Property
	! Value
	|-
	| ] (p<sub>c</sub>)
	| 5.83 MPa
	|-
	| ] (T<sub>c</sub>)
	| 78.45 °C (351 K)
	|-
	| ] (Z)
	| 0.9863
	|-
	| ] at constant pressure (C<sub>p</sub>) at 21 °C (70 °F)
	| 0.043 kJ·mol<sup>−1</sup>·K<sup>−1</sup>
	|-
	| ] at constant volume (C<sub>V</sub>) at 21 °C (70 °F)
	| 0.034 kJ·mol<sup>−1</sup>·K<sup>−1</sup>
	|-
	| ] (κ)
	| 1.253
	|}
	== Uses ==		== Synthesis ==
			Difluoromethane is primarily synthesized via ], by the reaction of ] and ] (HF), in the liquid phase using ] as a catalyst.<ref name=":2">{{Cite journal|last1=Shen|first1=Tao|last2=Ge|first2=Xin|last3=Zhao|first3=Hengjun|last4=Xu|first4=Zhixiong|last5=Tong|first5=Shaofeng|last6=Zhou|first6=Shaodong|last7=Qian|first7=Chao|last8=Chen|first8=Xinzhi|date=2020-07-01|title=A safe and efficient process for the preparation of difluoromethane in continuous flow|url=https://www.sciencedirect.com/science/article/pii/S1004954120300902|journal=Chinese Journal of Chemical Engineering|language=en|volume=28|issue=7|pages=1860–1865|doi=10.1016/j.cjche.2020.02.024|s2cid=216394634|issn=1004-9541}}</ref> Due to hydrogen fluoride's hazardous properties, a new process (based on the same reaction) was developed. The new process allows for ] of difluoromethane production through an isolated chamber.<ref name=":2" />
	Difluoromethane is a ] that has zero ]. Difluoromethane in an ] (50%/50%) w/w mixture with ] (]) is known as ], a common replacement for various ] (aka '']'') in new ] systems, especially for air-conditioning. The ] mix of Difluoromethane with ] (]) and ] (]) is known as ] through ] depending on the composition. Likewise the ] (48.2%/51.8% w/w) mixture with ] (R13). As a refrigerant difluoromethane is classified as A2L - slightly flammable . Although it has zero ozone depletion potential, it has ] 675 times that of carbon dioxide, based on a 100-year time frame .
			== Applications ==
			) in the lower atmosphere (]) at stations around the world. Abundances are given as pollution free monthly mean mole fractions in ].]]
			Difluoromethane is often used as a fire extinguishant due to its ability to undergo endothermic processes.<ref name=":32">{{Cite journal|last1=Blowers|first1=Paul|last2=Hollingshead|first2=Kyle|date=2009-05-21|title=Estimations of Global Warming Potentials from Computational Chemistry Calculations for CH 2 F 2 and Other Fluorinated Methyl Species Verified by Comparison to Experiment|url=https://pubs.acs.org/doi/10.1021/jp8114918|journal=The Journal of Physical Chemistry A|language=en|volume=113|issue=20|pages=5942–5950|doi=10.1021/jp8114918|pmid=19402663|bibcode=2009JPCA..113.5942B|issn=1089-5639}}</ref> Atmospheric concentration of difluoromethane at various latitudes since the year 2009 are shown to the left.
			]
			Difluoromethane is a molecule used as ] that has prominent heat transfer and pressure drop performance, both in condensation and vaporization.<ref>{{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}}</ref> It has a 100-year ] (GWP) of 675 times that of carbon dioxide, and an ] of nearly 5 years.<ref>May 2010 TEAP XXI/9 Task Force Report</ref> It is classified as A2L - slightly flammable by ASHRAE,<ref>2009 ASHRAE Handbook</ref> and has zero ] (ODP).<ref>{{Cite web | url=http://www.linde-gas.com/en/products_and_supply/refrigerants/hfc_refrigerants/r32/index.html |title = R32}}</ref> Difluoromethane is thus a relatively low-risk choice among ] refrigerants, most of which have higher GWP and longer persistence when leaks occur.
			The common refrigerant ] is a ], 50/50-mass-percent mixture of difluoromethane and ] (]). ] is a common replacement for various ] (i.e '']'') in new ] systems, especially for air-conditioning. The ] mix of difluoromethane with ] (]) and ] (]) is known as ] depending on the composition. Likewise, R-504 is the ] (48.2/51.8 mass%) mixture of difluoromethane and ] (R13). In 2011 17,949,893 metric tons of difluoromethane were emitted into the atmosphere in the United States alone.<ref>{{Cite journal|last1=Galka|first1=Michael D.|last2=Lownsbury|first2=James M.|last3=Blowers|first3=Paul|date=2012-12-04|title=Greenhouse Gas Emissions for Refrigerant Choices in Room Air Conditioner Units|url=https://pubs.acs.org/doi/10.1021/es302338s|journal=Environmental Science & Technology|language=en|volume=46|issue=23|pages=12977–12985|doi=10.1021/es302338s|pmid=23136858|bibcode=2012EnST...4612977G|issn=0013-936X}}</ref>
			Difluoromethane is currently used by itself in residential and commercial air-conditioners in Japan, China, and India as a substitute for ]. 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.<ref name="ReferenceA">{{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}}</ref>
			Many applications confirmed that difluoromethane exhibits heat transfer coefficients higher than those of ]
			under the same operating conditions but also higher frictional pressure drops.<ref name="ReferenceA"/>
			Other uses of difluoromethane include its use as aerosol propellants, blowing agents, and solvents.<ref name=":12" />
			==Environmental effects==
			Every year, approximately 15 kilotonnes of difluoromethane are produced.<ref name=":12" /> In gas form, the compound will degrade in the atmosphere by reaction with photochemically-produced hydroxyl radicals. This process will form ]. The ] for this process is estimated to be 4 years.<ref name=":12" /> Difluoromethane tends to enter the environment via the gas phase and accumulates there more commonly than in soils or sediments. Volatilization half-lives of this compound are about 45 minutes for rivers and 69 hours for lakes, difluoromethane does not ] in aquatic areas well.<ref name=":12" />
			HFC-32 released into the environment gets broken down into CF as an intermediate product. This goes on to create HF and CO<sub>2</sub> by hydrolysis in atmospheric water.<ref name=":12" />
			The ] (GWP) of HFC-32 is estimated at 677 on a 100-year time window.<ref>IPCC AR4, summarized at https://www.ghgprotocol.org/sites/default/files/ghgp/Global-Warming-Potential-Values%20%28Feb%2016%202016%29_1.pdf</ref> 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 ]s supplied in the United States Clean Air Act due to the ] being zero.<ref name=":12" /> Therefore, ] is not likely to be produced from this molecule.{{cn|date=June 2024}} Tropospheric ozone may lead to adverse health effects such as respiratory, cardiac or neurological damage. Additionally, ozone can affect plant and vegetation by inducing the bronzing of leaves.{{cn|date=June 2024}}
			== Toxicity ==
			Difluoromethane shows slight maternal and developmental toxicity at concentrations of approximately 50,000 ppm in rats, but not in rabbits. The exposure limitations set on difluoromethane for human use are 1,000 ppm, making exposure to dangerous levels unlikely.<ref name=":12" />
	== References ==		== References ==
	{{Reflist}}		{{Reflist}}
			== See also ==
			* ], a refrigerant that is being phased out, and which R-32 is a popular replacement for
			* ], another R-410A replacement
			* ]
	== External links ==		== External links ==
	*		* {{Webarchive|url=https://web.archive.org/web/20160920232053/http://www.fire.nist.gov/bfrlpubs/fire99/art047.html |date=2016-09-20 }}
	*		* {{Webarchive|url=https://web.archive.org/web/20160303180448/http://encyclopedia.airliquide.com/encyclopedia.asp?GasID=108 |date=2016-03-03 }}
	*		* {{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 }}
			*
	{{Organohalide-stub}}
	{{Halomethanes}}		{{Halomethanes}}
			{{fluorine compounds}}
			{{Authority control}}
	]		]
	]		]
			]
	]		]
	]
	]
	]
	]
	]
	]
	]
	]
	]
	]
	]