1,1-difluoroethane

Structural formula
General
Surname	1,1-difluoroethane
other names	R152a Freon 152a HFC-152a Ethylidene fluoride Ethylidene difluoride
Molecular formula	C 2 H 4 F 2
Brief description	colorless gas with a slightly sweet odor
External identifiers / databases
CAS number 75-37-6 EC number 200-866-1 ECHA InfoCard 100,000,788 PubChem 6368 Wikidata Q161285
properties
Molar mass	66.05 g mol −1
Physical state	gaseous
density	0.90 g cm −3 (liquid) 1.012 g cm −3 (liquid at boiling point) 3.0411 kg m −3 (gaseous at 0 ° C and 1013 hPa) 2.828 kg m −3 (gaseous at 15 ° C and 1013 hPa)
Melting point	−117 ° C
boiling point	−24.9 ° C
Vapor pressure	5.1 bar (20 ° C) 6.8 bar (30 ° C) 11.71 bar (50 ° C)
solubility	poor in water (3.2 g l −1 at 25 ° C)
Refractive index	1.3011 (−72 ° C)
safety instructions
GHS labeling of hazardous substances danger H and P phrases H: 220-280 P: 210-377-381-410 + 403
Toxicological data	> 1500 mg kg −1 ( LD 50 ,  rat ,  oral ) 977 g m −3 2 h −1 ( LC 50 ,  mouse ,  inh. )
Global warming potential	167 (based on 100 years)
Thermodynamic properties
ΔH f 0	−497.0 kJ / mol
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C

1,1-Difluoroethane is a chemical compound from the group of fluorocarbons . Under the designations R152a and HFC-152a , the substance is mainly used as a refrigerant .

Extraction and presentation

1,1-Difluoroethane can be obtained by a mercury- catalyzed addition of hydrogen fluoride to ethyne :

${\displaystyle \mathrm {HC{\equiv }CH+2\,HF\rightarrow H_{3}C{-}CHF_{2}} }$

The gas phase hydrogenation of 1,1-dichloro-2,2-difluoroethene or 1-chloro-2,2-difluoroethene also gives 1,1-difluoroethane.

${\displaystyle \mathrm {Cl_{2}C{=}CF_{2}+3\,H_{2}\rightarrow H_{3}C{-}CHF_{2}+2\,HCl} }$

${\displaystyle \mathrm {ClHC{=}CF_{2}+2\,H_{2}\rightarrow H_{3}C{-}CHF_{2}+HCl} }$

Another method of preparation is the addition of fluorine to ethene using xenon difluoride , although a product mixture of 45% 1,2-difluoroethane , 35% 1,1-difluoroethane and 20% 1,1,2-trifluoroethane is formed.

properties

1,1-Difluoroethane is a colorless gas that boils at −25 ° C at normal pressure . The heat of evaporation at the boiling point is 22.7 kJ mol ⁻¹ . According to Antoine, the vapor pressure function results accordingly

${\displaystyle \log _{10}\left(P(T)/{\text{bar}}\right)\;=\;A-{\frac {B}{T+C}}\qquad {\text{mit}}\qquad {\begin{cases}A=4{,}23406\\B=896{,}171~{\textrm {K}}\\C=-34{,}714~{\textrm {K}}\end{cases}}}$

in the temperature range from 160.7 K to 246.7 K. Solid 1,1-difluoroethane melts at −118.55 ° C with a heat of fusion of 1.57 kJ mol ⁻¹ . The triple point is −118.59 ° C and 0.6 mbar. The critical data known are the critical temperature with T _c = 113.5 ° C, the critical pressure with p _c = 44.9 bar and a critical density with σ _c = 0.365 g · cm ⁻³ . The compound is strongly polar with a dipole moment of 2.27 D , which causes a water solubility of 3.2 g / l at 25 ° C.

1,1-Difluoroethane forms flammable gas-air mixtures. The explosion range is between 4 vol% (112 g / m ³ ) as the lower explosion limit (LEL) and 18.5 vol% (518 g / m ³ ) as the upper explosion limit (UEL). The ignition temperature is 455 ° C. The substance therefore falls into temperature class T1.

safety instructions

In animal experiments, the gas was only toxic in rats and mice at extremely high doses. It was narcotic , drowsy and generally subdued in rats .

Individual evidence

1. ↑ ^{a b c d e f g h i j k l m} Entry on 1,1-difluoroethane in the GESTIS substance database of the IFA , accessed on May 20, 2019(JavaScript required) .
2. ↑ ^{a b c d} D. R. Lide: Handbook of Organic Solvents. P. 160, CRC Press, 1995, ISBN 978-0-8493-8930-6 .
3. ↑ ^{a b c d} Entry on 1,1-difluoroethane in the ChemIDplus database of the United States National Library of Medicine (NLM), accessed on July 31, 2018 or earlier.
4. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Physical Constants of Organic Compounds, pp. 3-172.
5. ^ ^{A b} National Technical Information Service. OTS0530083.
6. ↑ Toxicometric parameter of Industrial Toxic Chemicals Under Single Exposure, Izmerov, NF, et al., Moscow, Center of International Projects, GKNT, 1982, Pg. 54, 1982.
7. ↑ G. Myhre, D. Shindell et al .: Climate Change 2013: The Physical Science Basis . Working Group I contribution to the IPCC Fifth Assessment Report. Ed .: Intergovernmental Panel on Climate Change . 2013, Chapter 8: Anthropogenic and Natural Radiative Forcing, pp. 24-39; Table 8.SM.16 ( PDF ).
8. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Standard Thermodynamic Properties of Chemical Substances, pp. 5-22.
9. ^ Günter Siegemund, Werner Schwertfeger, Andrew Feiring, Bruce Smart, Fred Behr, Herward Vogel, Blaine McKusick: Fluorine Compounds, Organic . In: Ullmann's Encyclopedia of Industrial Chemistry , Wiley-VCH, Weinheim, 2002. doi : 10.1002 / 14356007.a11_349
10. ↑ Lacher, JR; Kianpour, A .; Oetting, F .; Park, JD: Reaction calorimetry. The hydrogenation of organic fluorides and chlorides in Trans. Faraday Soc. 52 (1956) 1500-1508, doi : 10.1039 / TF9565201500 .
11. ↑ e-EROS Encyclopedia of Reagents for Organic Synthesis , 1999–2013, John Wiley and Sons, Inc., entry for Xenon (II) fluoride, accessed January 20, 2018 .
12. ↑ Yang, N.-C .; Shieh, T.-C .; Feit, ED; Chernick, CL: Reactions of xenon fluorides with organic compounds in J. Org. Chem. 35 (1970) 4020-4024, doi : 10.1021 / jo00837a001 .
13. ^ Kul, I .; DesMarteau, DD; Beyerlein, AL: Vapor - liquid equilibria for CF ₃ OCF ₂ H / fluorinated ethane and CF ₃ SF ₅ / fluorinated ethane mixtures as potential R22 alternatives in Fluid Phase Equilibria 185 (2001) 241-253, doi : 10.1016 / S0378-3812 (01) 00474-5 .
14. ↑ D. R. Stull: Vapor Pressure of Pure Substances Organic Compounds . In: Ind. Eng. Chem . tape 39 , 1947, pp. 517-540 . , doi : 10.1021 / ie50448a022
15. ↑ Magee, JW: Molar Heat Capacity at Constant Volume of 1,1-Difluoroethane (R152a) and 1,1,1-Trifluoroethane (R143a) from the Triple-Point Temperature to 345 K at Pressures to 35 MPa in the International Journal of Thermophysics 19 (1998) 1397-1420, doi : 10.1023 / A: 1021983502589 .
16. ↑ Blanke, W .; Weiss, R .: Isochoric (p, v, T) measurements on 1,1-difluoroethane (R152a) in the liquid state from the triple point to 450 K and at pressures up to 30 MPa in Fluid Phase Equilib. 80 (1992) 179-190, doi : 10.1016 / 0378-3812 (92) 87066-V .
17. ↑ Blanke, W .; Weiss, R .: Thermodynamic properties of refrigerants. Part I: the triple points of the refrigerants R11, R12, R22, R142b, and 152a in PTB-Mitt. 101 (1991) 337-339.
18. ↑ ^{a b} Chemsafe database for safety-related parameters in explosion protection, PTB Braunschweig / BAM Berlin, accessed on May 21, 2019.
19. ↑ ^{a b} E. Brandes, W. Möller: Security-related characteristics - Volume 1: Flammable liquids and gases , Wirtschaftsverlag NW - Verlag für neue Wissenschaft GmbH, Bremerhaven 2003.