View source for Chemistry:1,2-Difluoroethane

{{chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 
| Name = 1,2-Difluoroethane
| ImageFileL1 = 1,2-difluoroethane.svg
| ImageFileR1 = 1,2-difluoroethane-from-xtal-view-1-Mercury-3D-balls.png
| ImageFileL2 = Valence structural formula of 1,2-Difluoroethane.svg
| ImageFileR2 = 1,2-difluoroethane-from-xtal-view-1-Mercury-3D-sf.png
| ImageSize = 
| ImageName = 
| PIN = 1,2-Difluoroethane
| OtherNames = 
|Section1={{Chembox Identifiers
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 11722
| InChI = 
| InChIKey = 
| ChEBI_Ref = 
| ChEBI = 
| EC_number = 
| EINECS = 200-866-1
| SMILES = C(CF)F
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/C2H4F2/c3-1-2-4/h1-2H2
| StdInChIKey_Ref = 
| StdInChIKey = AHFMSNDOYCFEPH-UHFFFAOYSA-N
| CASNo = 624-72-6
| CASNo_Ref = <ref>{{cite book|last1=Change|first1=Intergovernmental Panel on Climate|title=Safeguarding the Ozone Layer and the Global Climate System: Special Report of the Intergovernmental Panel on Climate Change|publisher=Cambridge University Press|isbn=9780521863360|page=[https://archive.org/details/ipccteapspecialr0000inte/page/469 469]|url=https://archive.org/details/ipccteapspecialr0000inte|url-access=registration|language=en|date=2005-10-24}}</ref>
| RTECS = 
| PubChem = 12223
| UNII = 2IQ22ABI8P
  }}
|Section2={{Chembox Properties
| C = 2 | F = 2 | H = 4
| Appearance = colourless liquid
| Density = 0.913
| MeltingPtK = 169
| BoilingPtC = 30.7
| MeltingPt_ref = <ref name=oect283/>
| Solubility = 2.31 g/L
| RefractIndex = 1.28 (liquid)
| SolubleOther = ether, benzene, chloroform
| LogP = 1.21
  }}

|Section3={{Chembox Structure
| CrystalStruct = monoclinic 
| SpaceGroup = ''C''2/''c''
| LattConst_a = 7.775
| LattConst_b = 4.4973
| LattConst_c = 9.024
| LattConst_beta = 101.73
| UnitCellVolume = 308.9
| UnitCellFormulas = 4
| LattConst_Comment = density 1.420

  }}
|Section4={{Chembox Structure
| CrystalStruct = Orthorhombic 
| SpaceGroup = ''P''2<sub>1</sub>2<sub>1</sub>2<sub>1</sub>
| LattConst_a = 8.047
| LattConst_b = 4.5086
| LattConst_c = 8.279
| LattConst_beta = 101.73
| UnitCellVolume = 300.4
| UnitCellFormulas = 4
| LattConst_Comment = density 1.461
  }}
}}
'''1,2-Difluoroethane''' is a saturated [[Chemistry:Hydrofluorocarbon|hydrofluorocarbon]] containing an atom of fluorine attached to each of two carbons atoms. The formula can be written CH<sub>2</sub>FCH<sub>2</sub>F.  It is an isomer of 1,1-difluoroethane.  It has a HFC name of '''HFC-152''' with no letter suffix.<ref name=nappa>{{cite journal|last1=Nappa|first1=Mario J.|last2=Sievert|first2=Allen C.|title=The chlorination of 1,2-difluoroethane (HFC-152)|journal=Journal of Fluorine Chemistry|date=June 1993|volume=62|issue=2–3|pages=111–118|doi=10.1016/S0022-1139(00)80085-8}}</ref>
When cooled to cryogenic temperatures it can have different conformers, gauche and trans.<ref>{{cite journal|last1=Huber-Wälchli|first1=P.|last2=Günthard|first2=Hs.H.|title=Trapping of unstable conformations from thermal molecular beams in argon matrices: 1,2-difluoroethane and 1,3-butadiene, i.r. spectra and conformer equilibria|journal=Spectrochimica Acta Part A: Molecular Spectroscopy|date=January 1981|volume=37|issue=5|pages=285–304|doi=10.1016/0584-8539(81)80159-6|bibcode=1981AcSpA..37..285H}}</ref> In the liquid form these are about equally abundant and easily interconvert.  As a gas it is mostly the gauche form.<ref>{{cite journal|last1=Klaboe|first1=Peter|last2=Nielsen|first2=J. Rud|title=Infrared and Raman Spectra of Fluorinated Ethanes. XIII. 1,2-Difluoroethane|journal=The Journal of Chemical Physics|date=1960|volume=33|issue=6|pages=1764|doi=10.1063/1.1731499|bibcode=1960JChPh..33.1764K}}</ref>

In the HFC-152 designation, 2 means two fluorine atoms, 5 means 5-1 or four hydrogen atoms, and 1 means 1+1 or two carbon atoms.<ref>{{cite book|last1=Kirk|first1=Raymond E.|last2=Othmer|first2=Donald F.|last3=Grayson|first3=Martin|title=Kirk-Othmer Encyclopedia of Chemical Technology|volume=11|page=282|edition=4}}</ref>

==Formation==
[[Chemistry:Ethylene|Ethylene]] reacts explosively with fluorine yielding a mixture of 1,2-difluoroethane and [[Chemistry:Vinyl fluoride|vinyl fluoride]].  With solid fluorine it will react when triggered by near-infrared radiation.<ref>{{cite journal|last1=Hauge|first1=R. H.|last2=Gransden|first2=S.|last3=Wang|first3=J. L. F.|last4=Margrave|first4=J. L.|title=Studies of the reactions of molecular fluorine with methane, acetylene, ethylene, allene, and other small hydrocarbons in matrices at low temperatures|journal=Journal of the American Chemical Society|date=November 1979|volume=101|issue=23|pages=6950–6954|doi=10.1021/ja00517a027}}</ref>

==Properties==
[[File:1,2-difluoroethane-from-xtal-conformation-depth-cue-Mercury-3D-balls.png|thumb|left|135px|The F-C-C-F [[Dihedral angle|dihedral angle]] in 1,2-difluoroethane is 68° in the crystal structure.<ref>{{ cite journal | doi = 10.1023/A:1027494101785 |author1= Floris Akkerman |author2=Jürgen Buschmann |author3=Dieter Lentz |author4=Peter Luger |author5=Eva Rödel | s2cid = 94249439 | title = Crystal and molecular structure of 1,2-difluoroethane and 1,2-diiodoethane | journal = Journal of Chemical Crystallography | year = 2003 | volume = 33 | issue = 12 | pages = 969–975 }}</ref>]]

Critical temperature is 107.5&nbsp;°C.<ref name=oect283>{{cite book|last1=Kirk|first1=Raymond E.|last2=Othmer|first2=Donald F.|last3=Grayson|first3=Martin|title=Kirk-Othmer Encyclopedia of Chemical Technology|volume=11|page=283|edition=4}}</ref>

If a C-H bond is over excited with too much vibration, the intramolecular vibrational relaxation takes 490 picoseconds.<ref>{{cite journal|last1=Bethardy|first1=G.A.|last2=Wang|first2=Xiaouang|last3=Perry|first3=David S.|title=The role of molecular flexibility in accelerating intramolecular vibrational relaxation|journal=Canadian Journal of Chemistry|date=March 1994|volume=72|issue=3|pages=652–659|doi=10.1139/v94-090|doi-access=free}}</ref>

The F-C-C-F dihedral angle is about 72°.<ref>{{cite web|url=http://www.dtic.mil/get-tr-doc/pdf?AD=ADA251286|archive-url=https://web.archive.org/web/20161220125936/http://www.dtic.mil/get-tr-doc/pdf?AD=ADA251286|url-status=dead|archive-date=December 20, 2016|publisher=Office of Naval Research|date=29 May 1992|author1=Steven W. Mork|author2=C. Cameron Miller|author3= Laura A. Philips|title=High Resolution Spectroscopy of 1,2-Difluoroethane in a Molecular Beam: A Case Study of Vibrational Mode-Coupling}}</ref> Natural bond orbital deletion bond calculations show that 1,2-difluoroethane prefers the gauche conformation due to hyperconjugation effects. Since F is much more electronegative than the C atom, it will have greater electron density for the bonding orbital (Carbon-fluorine bond). Thus, C will have larger σ* orbital, which is stabilized through C-H [[Chemistry:Hyperconjugation|hyperconjugation]]. This cis C-H bonds and the C-F σ* interactions are significant. The dihedral angle of about 72° is a result of decreasing hyper conjugative stability and decreasing steric destabilization.<ref>{{Cite journal | doi=10.1021/jp046290d| title=Gauche Effect in 1,2-Difluoroethane. Hyperconjugation, Bent Bonds, Steric Repulsion| year=2005| last1=Goodman| first1=Lionel| last2=Gu| first2=Hongbing| last3=Pophristic| first3=Vojislava| journal=The Journal of Physical Chemistry A| volume=109| issue=6| pages=1223–1229| pmid=16833433| bibcode=2005JPCA..109.1223G}}</ref>

==Reactions==
CH<sub>2</sub>FCH<sub>2</sub>F reacts with chlorine when treated with light. Two products are formed CH<sub>2</sub>FCCl<sub>2</sub>F and CHClFCHClF. The proportions of each depends on the solvent.<ref name=nappa/>

==Uses== 
1,2-Difluoroethane is primarily used in Refrigerants, 39%; foam blowing agents, 17%; solvents, 14%; fluoropolymers, 14%; sterilant gas, 2%; aerosol propellants, 2%; food freezant, 1%; other, 8%; exports, 3%.<ref name="1,2-DIFLUOROETHANE {{!}} C2H4F2">{{cite web|title=1,2-DIFLUOROETHANE {{!}} C2H4F2|url=https://pubchem.ncbi.nlm.nih.gov/compound/1_2-difluoroethane#section=Environmental-Fate|website=pubchem.ncbi.nlm.nih.gov}}</ref>

==Safety== 
1,2-Difluoroethane is toxic when inhaled or when it comes into direct contact with the skin. Fluorocarbons are 4 to 5 times heavier than air, so it tends to concentrate in low-lying areas. This increases the risk of inhalation. 1,2-difluoroethane is toxic to humans through several mechanisms. First, because it has a high density, it can displace oxygen in the lungs causing suffocation. In addition, inhaled fluorocarbons causes the myocardium to become more sensitive to catecholamines, which results in deadly cardiac arrhythmias.<ref>{{Cite web|url=https://toxnet.nlm.nih.gov/cgi-bin/sis/search/a?dbs+hsdb:@term+@DOCNO+6786|title = Toxnet Has Moved}}</ref>

When inhaled by rats, 1,2-difluoroethane is converted to fluoroacetate using [[Biology:Cytochrome P450|cytochrome P450]] and then to fluorocitrate both toxic. 100 parts per million in the atmosphere was sufficient to poison rats in 30 minutes and to kill them in four hours. 1,2-Difluoroethane is likely to be similarly toxic to humans.<ref>{{cite journal|last1=KELLER|first1=DOUGLAS A.|last2=ROE|first2=D. CHRISTOPHER|last3=LIEDER|first3=PAUL H.|date=1996|title=Fluoroacetate-Mediated Toxicity of Fluorinated Ethanes|journal=Toxicological Sciences|volume=30|issue=2|pages=213–219|doi=10.1093/toxsci/30.2.213|pmid=8812268|doi-access=free}}</ref>

==Environmental fate==
1,2-Difluoroethane can enter the environment various ways. One way is through volatilization from rivers and lakes. [[Physics:Henry's law|Henry's law]] estimates that the volatilization half life from a model river is about 2.4 hours and 3.2 days from a model lake.<ref name="1,2-DIFLUOROETHANE {{!}} C2H4F2"/>
When 1,2-difluoroethane is released to the environment, it will end up in the atmosphere.  Here it is degraded by reaction with [[Chemistry:Hydroxyl radical|hydroxyl radical]]s and oxygen.<ref name="walli">{{cite journal|last1=Wallington|first1=Timothy J.|last2=Hurley|first2=Michael D.|last3=Ball|first3=James C.|last4=Ellermann|first4=Thomas|last5=Nielsen|first5=Ole J.|last6=Sehested|first6=Jens|title=Atmospheric Chemistry of HFC-152: UV Absorption Spectrum of CH<sub>2</sub>FCFHO<sub>2</sub> Radicals, Kinetics of the Reaction CH<sub>2</sub>FCFHO<sub>2</sub> + NO → CH<sub>2</sub>FCHFO + NO<sub>2</sub>, and Fate of the Alkoxy Radical CH<sub>2</sub>FCFHO|journal=The Journal of Physical Chemistry|date=May 1994|volume=98|issue=21|pages=5435–5440|doi=10.1021/j100072a008|bibcode=1994JPhCh..98.5435W}}</ref>

CH<sub>2</sub>FCH<sub>2</sub>F + OH → CH<sub>2</sub>FCHF + H<sub>2</sub>O

CH<sub>2</sub>FCHF + O<sub>2</sub> → CH<sub>2</sub>FCHFO<sub>2</sub> peroxy radical

CH<sub>2</sub>FCHFO<sub>2</sub> + NO → CH<sub>2</sub>FCHFO alkoxy radical

When catalysed by chlorine atoms and oxidised by nitrogen oxides the end product is HCOF which can decompose further to [[Chemistry:Hydrofluoric acid|HF]] and [[Chemistry:Carbon monoxide|CO]].<ref name="walli"/>

The halflife in air is between 140 and 180 days.<ref name="1,2-DIFLUOROETHANE {{!}} C2H4F2"/>

==Control==
1,2-Difluoroethane is a [[Chemistry:Greenhouse gas|greenhouse gas]] when released to the atmosphere. It has a warming equivalent to 140 times that of carbon dioxide. As such it may be controlled by government regulation.  The Australian government classifies 1,2-difluoroethane as an exotic synthetic greenhouse gas.<ref>{{cite web|title=Ozone Protection and Synthetic Greenhouse Gas Management Amendment Regulations 2004 (No 1)|date=7 September 2004|url=https://www.legislation.gov.au/Details/F2004B00325/589b856f-5df9-459a-9da1-41ce950265f9|accessdate=7 December 2016}}</ref>

==References==
{{Reflist}}

{{DEFAULTSORT:Difluoroethane, 1, 2-}}
[[Category:Fluoroalkanes]]

{{Sourceattribution|1,2-Difluoroethane}}