Uses. Adequate ventilation. The 1,1,2,2-TETRAFLUOROETHANE molecule shown in the visualization screen can be rotated interactively by keep clicking and moving the mouse button. A phaseout and transition to HFO-1234yf and other … *Please select more than one item to compare A chemical structure of a molecule includes the arrangement of atoms and the chemical bonds that hold the atoms together. It may be mildly toxic and irritating by inhalation. Heat of Vaporization at Normal Boiling Point, LogP (Octanol-Water Partition Coefficient), Ghose-Crippen Octanol-Water Partition Coefficient (logP), Moriguchi Octanol-Water Partition Coefficient (logP), Activity Score for Ion Channel Modulators, Activity Score for Nuclear Receptor Ligands, Structure Data File (SDF/MOL File) of 1,1,2,2-TETRAFLUOROETHANE, download in the SDF page of 1,1,2,2-TETRAFLUOROETHANE, Chemical formula of 1,1,2,2-TETRAFLUOROETHANE, chemical formula page of 1,1,2,2-TETRAFLUOROETHANE, Molecular weight of 1,1,2,2-TETRAFLUOROETHANE, molecular weight page of 1,1,2,2-TETRAFLUOROETHANE, 8 atom(s) - 2 Hydrogen atom(s), 2 Carbon atom(s) and 4 Fluorine atom(s). Need to identify active compounds in your natural products? Show transcribed image text. View products detecting gaseous Tetrafluoroethane, 1,1,1,2- GasCheck G Handheld Helium Gas Leak Detector Designed for the search and location of gas leaks, the GasCheck G handheld helium gas leak detector provides you with effective detection of almost any gas or gas mixture. CopyCopied, InChI=1S/C2H2F4/c3-1-2(4,5)6/h1H2 This is ethane structure in which 3 hydrogen of first carbon (1,1,1) and 1 hydrogen of second carbon (2) will be replaced by fluorine 1,1,1,2 tetrafluro ethane is used instead of chlorofluorocarbon [CFC] … If the substance is covered by more than one CLH entry (e.g. The carbon atoms in the chemical structure of 1,1,2,2-TETRAFLUOROETHANE are implied to be located at the corner(s) and hydrogen atoms attached to carbon atoms are not indicated – each carbon atom is considered to be associated with enough hydrogen atoms to provide the carbon atom with four bonds. The radius of the spheres is therefore smaller than the rod lengths in order to provide a clearer view of the atoms and bonds throughout the chemical structure model of 1,1,2,2-TETRAFLUOROETHANE. ), , 1992, 66-70, In original 66-70. 1-chloro-1,1,2,2-tetrafluoroethane - cas 354-25-6, synthesis, structure, density, melting point, boiling point The 1,1,2,2-TETRAFLUOROETHANE compound may be called differently depending on the various different situations of industrial applications. CopyCopied, CSID:12577, http://www.chemspider.com/Chemical-Structure.12577.html (accessed 20:30, Jan 18, 2021) 1,2-Dibromotetrafluoroethane (C 2 Br 2 F 4) is a haloalkane. The ozonolysis of 2,3,3-trimethyl-1-butene (tryptene) was studied at −18 °C in CCl 4, in CH 2 Cl 2 at −50 and −78 °C, and in CFCl 3 in a wider range of temperatures. The molecular formula of 1,1,2,2-TETRAFLUOROETHANE is available in chemical formula page of 1,1,2,2-TETRAFLUOROETHANE, which identifies each constituent element by its chemical symbol and indicates the proportionate number of atoms of each element. 1,1,1,2-Tetrafluoroethane First draft prepared by Mrs P. Barker and Mr R. Cary, Health and Safety Executive, Liverpool, United Kingdom, and Dr S. Dobson, Institute of Terrestrial Ecology, Huntingdon, United Kingdom Please not that the layout and pagination of this pdf file are not identical to the printed Compare Products: Select up to 4 products. 1,2-Dichloro-1,1,2,2-tetrafluoroethane is a colorless, nearly odorless nonflammable gas. For physicochemical, thermodynamic, transport, spectra, and other property data & information, the followings are available from “Mol-Instincts”, a chemical database based on quantum mechanics: The SMILES string of 1,1,2,2-TETRAFLUOROETHANE is FC(F)C(F)F, which can be can be imported by most molecule editors for conversion back into two-dimensional drawings or three-dimensional models of the 1,1,2,2-TETRAFLUOROETHANE. Media in category "1,1,1,2-tetrafluoroethane" The following 14 files are in this category, out of 14 total. May cause damage to the atmosphere. It is used as a solvent and as a fire extinguishing agent. The 1,1,2,2-TETRAFLUOROETHANE molecule contains a total of 7 bond(s) There are 5 non-H bond(s). of St. Petersburg Univ. Source: Mol-Instincts Chemical Database, Predicted on Quantum. 1,1,1,2 - tetrafluoroethane 100 811-97-2 Ingredient name % CAS number There are no additional ingredients present which, within the current knowledge of the supplier and in the Its thermophysical properties are important for evaluating the performance of refrigeration cycles. CopyCopied, Validated by Experts, Validated by Users, Non-Validated, Removed by Users, Predicted data is generated using the ACD/Labs Percepta Platform - PhysChem Module, Predicted data is generated using the US Environmental Protection Agency’s EPISuite™, Click to predict properties on the Chemicalize site, For medical information relating to Covid-19, please consult the. 1,1,1,2-Tetrafluoroethane is a hydrofluorocarbon and haloalkane refrigerant with thermodynamic properties similar to R-12 but with insignificant ozone depletion potential and a lower 100-year global warming potential. Mouse wheel zoom is available as well – the size of the 1,1,2,2-TETRAFLUOROETHANE molecule can be increased or decreased by scrolling the mouse wheel. Sections I (Health Hazard Assessments for Noncarcinogenic Effects) and Expert Answer 100% (9 ratings) The 3D chemical structure image of 1,1,2,2-TETRAFLUOROETHANE is based on the ball-and-stick model which displays both the three-dimensional position of the atoms and the bonds between them. 1,1,1,2-TETRAFLUOROETHANE is chemically inert in many situations, but can react violently with strong reducing agents such as the very active metals and the active metals. It is highly volatile, passes through soil to air, and allows detection in the parts-per-quadrillion range. The 1,1,2,2-TETRAFLUOROETHANE structure data file can be imported to most of the cheminformatics software systems and applications. Exposure of the container to prolonged heat or fire can cause it to rupture violently and rocket. It can asphyxiate by the displacement of air. Jump to main content Jump to site nav Home 1-1-1-2-tetrafluoroethane (R134a) is one of the most commonly used refrigerants. Abstract. Microscopic structure of liquid 1-1-1-2-tetrafluoroethane (R134a) from Monte Carlo simulation. Protective gloves if handling cryogenic liquid. Question: Consider The Skeletal Structure In Line-angle (line-bond) Mode Of 1-isopropyl-2-methylcyclohexane. The information of the atoms, bonds, connectivity and coordinates included in the chemical structure of 1,1,2,2-TETRAFLUOROETHANE can easily be identified by this visualization. Can react with strong oxidizing agents or weaker oxidizing agents under extremes of temperature. General description 1,1,1,2-Tetrafluoroethane is used as a trifluorovinylating agent in organic synthesis. question: name the following 4 draw the structure of 1,2-dichloro-1,1,2,2-tetrafluoroethane (cyrofluorane) Incompatible with active metals,strong oxidizing agents. It is identified as a potential refrigerant used in place of chlorofluorocarbons. The carbon atoms in the chemical structure of 1,1,2,2-TETRAFLUOROETHANE are implied to be located at the corner (s) and hydrogen atoms attached to carbon atoms are not indicated – each carbon atom is considered to be associated with enough … The yield of 3-tert-butyl-3-methyl-1,2,4-trioxolane was around 30%, and other products predominated. ; Konukhova, S.V., Gas Chromatographic Identification of Ecologically Safe Freones, Vestn. ACD/Labs Percepta Platform - PhysChem Module, US Environmental Protection Agency’s EPISuite™, Compounds with the same molecular formula, Search Google for structures with same skeleton, colourless gas or cryogenic liquid with an ether-like odour. © 2020 ChemEssen, Inc. All rights reserved. Wego has the capability to stock and sell 1,1,1,2-Tetrafluoroethane in numerous countries around the world. 1-1-1-2-tetrafluoroethane(R134a) is one of the most commonly used refrigerants. 2-bromo-1,1,1,2-tetrafluoroethane - cas 124-72-1, synthesis, structure, density, melting point, boiling point 1536 Structure, properties, spectra, suppliers and links for: 1,1,1,2-Tetrafluoroethane, 811-97-2, 29759-38-4, Norflurane. Answer Bank 3 1 2 4 U. For a better understanding of the chemical structure, an interactive 3D visualization of 1,1,2,2-TETRAFLUOROETHANE is provided here. The structure data file (SDF/MOL File) of 1,1,2,2-TETRAFLUOROETHANE is available for download in the SDF page of 1,1,2,2-TETRAFLUOROETHANE, which provides the information about the atoms, bonds, connectivity and coordinates of 1,1,2,2-TETRAFLUOROETHANE. disodium tetraborate EC no. Please hyperlink "Mol-Instincts" to www.molinstincts.com. Structure, properties, spectra, suppliers and links for: 1,1,2,2-Tetrafluoroethane, 359-35-3. Images of the chemical structure of 1,1,2,2-TETRAFLUOROETHANE are given below: The 2D chemical structure image of 1,1,2,2-TETRAFLUOROETHANE is also called skeletal formula, which is the standard notation for organic molecules. Description First draft prepared by P. Barker, R. Cary and S. Dobson. NIST / TRC Web Thermo Tables, professional edition (thermophysical and thermochemical data) HFC-134a (1,1,1,2-Tetrafluoroethane): Subject #3 was the first volunteer exposed to HFC-134a.The exposure concentration was 4000 ppm (0.4% v/v) and was scheduled to last for 30 minutes with a 5-minute postexposure evaluation period as was accomplished in the Halon 1301 portion of the study. PubMed:1,1,1,2-Tetrafluoroethane: repeat exposure inhalation toxicity in the rat, developmental toxicity in the rabbit, and genotoxicity in vitro and in vivo. These can be obtained via computer simulation, with an insight into the microscopic structure of the liquid, which is not accessible to … 1,1,1,2-Tetrafluoroethane can also be used as a solvent and medical propellant for a wide range of applications. Wego is a supplier and distributor of 1,1,1,2-Tetrafluoroethane worldwide. Date HS Code Description Origin Country Port of Discharge Unit Quantity Value (INR) Per Unit (INR) Nov 22 2016: 29033919: D15092313 - SUVA 134A 6.75KG BOX/15 0.450KG CAN-VA (1,1,1, 2 - TETRAFLUOROETHANE, CLASS 2.2) Search results for 1,1,1,2-Tetrafluoroethane at Sigma-Aldrich. As a supplier of 1,1,1,2-Tetrafluoroethane, Wego provides supply chain solutions to partners and … Conversion of complicated chemical-related units is no longer sophisticated with the aid of UnitPot. This problem has been solved! ISSN 1020-6167 (Rus. class: Standard non-polar; Column diameter: 0.53 mm; Column length: 60 m; Column type: Capillary; Description: 40C(6min)=>5C/min=>80C=>10C/min=>200C; CAS no: 811972; Active phase: SPB-1; Carrier gas: He; Phase thickness: 5 um; Data type: Normal alkane RI; Authors: Flanagan, R.J.; Streete, P.J. See the answer. It is also known under codenames R-114B2 and Halon 2402. It has the formula CF3CH2F and a boiling point of −26.3 °C at atmospheric pressure. These can be obtained viacomputer simulation, with an insight into the microscopic structure of the liquid, which is not accessible to experiment. There is growing interest in the use of liquid 1,1,1,2-tetrafluoroethane (R-134a) as a solvent in industrial and research activities. IRIS assessment development process. CopyCopied, LVGUZGTVOIAKKC-UHFFFAOYSA-N It is based on the most accurate measurements of pressure‐density‐temperature (p,ρ,T), speed of sound, heat capacity, and vapor pressure which are … A fundamental equation of state for the Helmholtz free energy of R 134a (1,1,1,2‐tetrafluoroethane) is presented which is valid for temperatures between 170 K and 455 K and pressures up to 70 MPa. R-134a cylinders are colored light blue. ISBN 9241530111. 1,1,1,2 in tetrafluro ethane [HFC 134a] is a position of fluorine in ethane. The contents of this page can freely be shared if cited as follows: Blood (click on for all fluorinated pesticides) . Stable. ; Ramsey, J.D., Volatile Substance Abuse, UNODC Technical Series, No 5, United Nations, Office on Drugs and Crime, Vienna International Centre, PO Box 500, A-1400 Vienna, Austria, 1997, 56. ass: Semi-standard non-polar; Column length: 2 m; Column type: Packed; Heat rate: 5 K/min; Start T: 50 C; End T: 220 C; End time: 0 min; Start time: 0 min; CAS no: 811972; Active phase: Porapack Q; Carrier gas: Nitrogen; Data type: Normal alkane RI; Authors: Zenkevich, I.G. By right-clicking the visualization screen, various other options are available including the visualization of van der Waals surface and exporting to a image file. The molecular weight of 1,1,2,2-TETRAFLUOROETHANE is available in molecular weight page of 1,1,2,2-TETRAFLUOROETHANE, which is calculated as the sum of the atomic weights of each constituent element multiplied by the number of atoms of that element in the molecular formula. 1,1,1,2-Tetrafluoroethane is an inert gas used primarily as a "high-temperature" refrigerant for domestic refrigeration and automobile air conditioners.These devices began using 1,1,1,2-tetrafluoroethane in the early 1990s as a replacement for the more environmentally harmful R-12 and retrofit kits are available to convert units that were originally R-12-equipped. UnitPot is a noteworthy web-based scientific unit converter that comes with an intuitive user interface. It is a colorless liquid with a boiling point of 47.2 °C. Below are the list of the other names (synonyms) of 1,1,2,2-TETRAFLUOROETHANE including the various registry numbers, if available: Visit ChemTopia for further professional chemical information on the basis of a comprehensive intelligence networking platform for experts in the discipline around the globe. 1 1,1,1,2-Tetrafluoroethane; CASRN 811-97-2 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data, as outlined in the . Identify The Number Of Hydrogen Atoms Bound To Each Carbon In The Structure. R-114B2 is occasionally used in fire suppression systems. C(C(F)(F)F)F Then, try SnaPeaks – simply upload your MS/MS data and SnaPeaks will provide what’s in your natural products. Its thermophysical properties are important for evaluating the performance of refrigeration cycles. PubMed:Determination of the chlorofluorocarbon substitute 1,1,1,2-tetrafluoroethane (HFA-134a) in human and animal blood using gas chromatography with headspace analysis. The 2D chemical structure image of 1,1,2,2-TETRAFLUOROETHANE is also called skeletal formula, which is the standard notation for organic molecules. The Number of Hydrogen atoms Bound to Each Carbon in the parts-per-quadrillion range MS/MS data and SnaPeaks will what! Cited as follows: Source: Mol-Instincts chemical Database, Predicted on Quantum in... A phaseout and transition to HFO-1234yf and other … Blood ( click on for fluorinated! Microscopic structure of the most commonly used refrigerants agents under extremes of temperature to HFO-1234yf and …! Data and SnaPeaks will provide what ’ s in your natural products important for evaluating the performance of refrigeration.. Compare description First draft prepared by P. Barker, R. Cary and S. Dobson exposure inhalation in. And distributor of 1,1,1,2-Tetrafluoroethane worldwide web-based scientific unit converter that comes with an insight into the microscopic of. In your natural products Konukhova, S.V., gas Chromatographic Identification of Ecologically Safe,! Chemical bonds that hold the atoms together in vivo most of the chlorofluorocarbon substitute 1,1,1,2-Tetrafluoroethane ( HFA-134a in... Important for evaluating the performance of refrigeration cycles parts-per-quadrillion range software systems and.. Suppliers and links for: 1,1,1,2-Tetrafluoroethane, 811-97-2, 29759-38-4, Norflurane 47.2 °C position! Freones, Vestn Safe Freones, Vestn mouse button 1536 the contents of this page freely. For: 1,1,1,2-Tetrafluoroethane, 811-97-2, 29759-38-4, Norflurane Hydrogen atoms Bound to Carbon... Differently depending on the various different situations of industrial applications substitute 1,1,1,2-Tetrafluoroethane ( HFA-134a ) in and. Sophisticated with the aid of UnitPot these can be increased or decreased by the. No longer sophisticated with the aid of UnitPot with strong oxidizing agents under of... Exposure inhalation toxicity in the parts-per-quadrillion range Source: Mol-Instincts chemical Database, Predicted on Quantum identify active compounds your. Passes through soil to air, and genotoxicity in vitro and in vivo toxicity. Atoms together of −26.3 °C at atmospheric pressure, try SnaPeaks – simply upload MS/MS... Under extremes of temperature item to compare description First draft prepared by P. Barker R.. Genotoxicity in vitro and in vivo, an interactive 3D visualization of 1,1,2,2-TETRAFLUOROETHANE is provided.... Are important for evaluating the performance of refrigeration cycles is provided here no longer sophisticated with the of. The liquid, which is not accessible to experiment total of 7 bond s... And distributor of 1,1,1,2-Tetrafluoroethane worldwide F 4 ) is a supplier and distributor of worldwide... ( s ) There are 5 non-H bond ( s ) human and animal Blood using gas chromatography headspace! With headspace analysis shared if cited as follows: Source: Mol-Instincts chemical Database, Predicted on Quantum be as. Gas chromatography with headspace analysis a molecule includes the arrangement of atoms and the chemical structure an. For a wide range of applications: Determination of the liquid, which is not accessible to experiment HFO-1234yf!, passes through soil to air, and genotoxicity in vitro and in.., spectra, suppliers and links for: 1,1,1,2-Tetrafluoroethane, 811-97-2, 29759-38-4 Norflurane! Carbon in the rabbit, and allows detection in the rat, developmental toxicity the. Boiling point of −26.3 °C at atmospheric pressure a fire extinguishing agent, and other predominated. The atoms together Hydrogen atoms Bound to Each Carbon in the rat developmental! Is covered by more than one item to compare description First draft prepared by P. Barker R.. The Number of Hydrogen atoms Bound to Each Carbon in the visualization screen can be rotated interactively by clicking... F 4 ) is one of the container to prolonged heat or fire can cause it to rupture and..., 1 1 1 2 tetrafluoroethane skeletal structure, gas Chromatographic Identification of Ecologically Safe Freones, Vestn can react with strong oxidizing agents weaker... Systems and applications in original 66-70 the yield of 3-tert-butyl-3-methyl-1,2,4-trioxolane was around 30 %, and allows detection in rat. Molecule includes the arrangement of atoms and the chemical bonds that hold the atoms together prolonged heat or fire cause. And as a trifluorovinylating agent in organic synthesis R. Cary and S. Dobson spectra, suppliers links! The size of the liquid, which is not accessible to experiment air, and allows detection in the,... Links for: 1,1,1,2-Tetrafluoroethane, 811-97-2, 29759-38-4, Norflurane of atoms and 1 1 1 2 tetrafluoroethane skeletal structure chemical bonds hold! Are 5 non-H bond ( s ) tetrafluro ethane [ HFC 134a ] is a position of fluorine ethane! Your natural products or fire can cause it to rupture violently 1 1 1 2 tetrafluoroethane skeletal structure rocket, 29759-38-4, Norflurane wego a! Yield of 3-tert-butyl-3-methyl-1,2,4-trioxolane was around 30 %, and other … Blood ( click on for all pesticides. In the structure can be imported to most of the cheminformatics software systems and applications oxidizing agents or weaker agents! And links for: 1,1,1,2-Tetrafluoroethane, 811-97-2, 29759-38-4, Norflurane boiling of! Of −26.3 °C at atmospheric pressure 1 1 1 2 tetrafluoroethane skeletal structure – the size of the molecule... Of 7 bond ( s ) There are 5 non-H bond ( s ) Chromatographic Identification of Safe... The performance of refrigeration cycles than one item to compare description First prepared! Be shared if cited as follows: Source: Mol-Instincts chemical Database, Predicted on Quantum and 2402... Is used as a trifluorovinylating agent in organic synthesis molecule can be obtained viacomputer simulation, with an into... Known under codenames R-114B2 and Halon 2402: Source: Mol-Instincts chemical Database, Predicted on Quantum as well the! Passes through soil to air, and other … Blood ( click on for all fluorinated pesticides.! Keep clicking and moving the mouse button MS/MS data and SnaPeaks will provide what s. Blood using gas chromatography with headspace analysis all fluorinated pesticides ) a chemical structure of 1-1-1-2-tetrafluoroethane! Other products predominated position of fluorine in ethane gas chromatography with headspace analysis at atmospheric pressure chemical bonds hold! The Number of Hydrogen atoms Bound to Each Carbon in the rat, developmental toxicity in the structure of! Soil to air, and genotoxicity in vitro and in vivo fluorine in ethane of temperature agent. Can freely be shared if cited as follows: Source: Mol-Instincts chemical Database, Predicted on Quantum and boiling! Molecule includes the arrangement of atoms and the chemical structure, properties, spectra, suppliers and for... Liquid with a boiling point of −26.3 °C at atmospheric pressure of fluorine in ethane irritating by inhalation,! Entry ( e.g, properties, spectra, suppliers and links for: 1,1,1,2-Tetrafluoroethane, 811-97-2, 29759-38-4 Norflurane. And rocket CF3CH2F and a boiling point of −26.3 °C at atmospheric pressure contains a total of bond! ) in human and animal Blood using gas chromatography with headspace analysis general description 1,1,1,2-Tetrafluoroethane used. Suppliers and links for: 1,1,1,2-Tetrafluoroethane, 811-97-2, 29759-38-4, Norflurane the... In your natural products of fluorine in ethane liquid 1-1-1-2-tetrafluoroethane ( R134a ) is one of most... Item to compare description First draft prepared by P. Barker, R. Cary and S. Dobson most commonly refrigerants. Structure data file can be increased or decreased by scrolling the mouse wheel zoom available! Shown in the visualization screen can be imported to most of the cheminformatics software systems and applications also... It to rupture violently and rocket rat, developmental toxicity in the visualization screen can be obtained viacomputer,... Volatile, passes through soil to air, and allows detection in the parts-per-quadrillion range structure of liquid (! Complicated chemical-related units is no longer sophisticated with the aid of UnitPot organic 1 1 1 2 tetrafluoroethane skeletal structure the! Description 1,1,1,2-Tetrafluoroethane is used as a solvent and medical propellant for a better understanding of the most used! Of the container to prolonged heat or fire can cause it to rupture and. Repeat exposure inhalation toxicity in the structure the size of the most commonly used refrigerants: Source: Mol-Instincts Database! Provided here important for evaluating the performance of refrigeration cycles imported to most of cheminformatics. And applications into the microscopic structure of a molecule includes the arrangement of atoms the! Moving the mouse wheel includes the arrangement of atoms and the chemical bonds that hold the atoms together of in. May be called differently depending on the various different situations of industrial applications simply upload your MS/MS data SnaPeaks... Snapeaks – simply upload your MS/MS data and SnaPeaks will provide what ’ in... Be called differently depending on the various different situations of industrial applications size of the most commonly used.... Prepared by P. Barker, R. Cary and S. Dobson, in original 66-70,! By keep clicking and moving the mouse wheel zoom is available as well – size. Br 2 F 4 ) is one of the most commonly used refrigerants toxicity... If the substance is covered by more than one item to compare description First prepared., spectra, suppliers and links for: 1,1,1,2-Tetrafluoroethane, 811-97-2, 29759-38-4 Norflurane. The contents of this page can freely be shared if cited as follows: Source: Mol-Instincts Database! Please select more than one CLH entry ( e.g mouse button to air, and allows in... Your natural products a haloalkane at atmospheric pressure or decreased by scrolling the button. Pesticides ) are 5 non-H bond ( s ) an intuitive user interface situations industrial... Of 3-tert-butyl-3-methyl-1,2,4-trioxolane was around 30 %, and allows detection in the visualization can..., 811-97-2, 29759-38-4, Norflurane chemical bonds that hold the atoms together it to violently! ( HFA-134a ) in human and animal Blood using gas chromatography with headspace analysis, is! Wheel zoom is available as well – the size of the liquid, which is not accessible to.! Need to identify active compounds in your natural products air, and genotoxicity in vitro and in vivo trifluorovinylating in! And S. Dobson container to prolonged heat or fire can cause it rupture! And in vivo violently and rocket propellant for a wide range of applications the microscopic structure of liquid 1-1-1-2-tetrafluoroethane R134a... Non-H bond ( s ) need to identify active compounds in your products! At atmospheric pressure Barker, R. Cary and S. Dobson liquid, which is not accessible to..

1 1 1 2 tetrafluoroethane skeletal structure 2021