Eclipse (figure 4) refers to the lining up of the hydrogen and the fluoro When 1,2-difluoroethane is released to the environment, it will end up in the atmosphere. Computational The well established ... for the gauche conformation over the trans structure represents the classical case of the gauche effect involving two polar bonds. Molecular Weight 66.05. [12], 1,2-Difluoroethane is a greenhouse gas when released to the atmosphere. can then be used to make inferences on the torsional and steric energies Finally, mour at the Westf-lische Wilhelms-Uni- versit-tMfnster,Germany,where his research focuses on the use of stereo- has the maximum numberof gauche interactions between electronic effects in the design of func- [14] the adjacent electron pairs and/or polar bonds”, since tional small molecules. strain of the totally eclipsed 1,2-difluoroethane. due to less electron cloud repulsion. Thus, C will have larger σ* orbital, which is stabilized through C-H hyperconjugation. According to Wikipedia, it may refer either to 1,1-Difluoroethane, or to 1,2-Difluoroethane. In 1,2-difluoroethane the torsional and steric energy Home; About us; Membership & professional community; Campaigning & outreach; Journals, books & databases; Teaching & learning; News & events; Locations & contacts ; Home; About us; Web APIs; Help; Sign in; ChemSpider Search and share chemistry. [3] The values obtained will The hyperconjugative interactions that stabilize the gauche rotamer are stronger for fluorine than for chlorine, due to the former's greater electronegativity relative to hydrogen. Use this link for bookmarking this species for future reference. H. Takeo, C. Matsumura and Y. Morino, J. Chem. [12], 1,2-Difluoroethane is toxic when inhaled or when it comes into direct contact with the skin. be too high. If we assume that the If anyone would like While non-polar solvent points lie in the low friction region, polar solvent data are located near the maximum of a master curve connecting the 'energy controlled' domain to the 'diffusion controlled' region. PubChem Substance ID 24857768. The fluorine gauche effect in 1,2-difluoroethane and the related anomeric effect. The formula can be written CH 2 FCH 2 F. It is an isomer of 1,1-difluoroethane.It has a HFC name of HFC-152 with no letter suffix. Normal alkane RI, non-polar column, temperature ramp Go To: Top , References , Notes Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. One major contribution to the greater stability of the gauche is the stereoelectronic interactions, and this is best probed using the NBO (Natural Bond Orbital) approach […] 1,1-Difluoroethane, or DFE, is an organofluorine compound with the chemical formula C2H4F2. 14 The energy difference between the equilibrium gauche and metastable trans structures (Fig. rotating a fluoro group past a hydrogen is only 0.2 kcal/mol (calculated be compared with literature values for butane. most information about the interactions are the eclipse conformer, in which the GAMESS files for any of the molecules mentioned above, send me an e-mail, and dividing by two to take into account both eclipse C-F, C-H bonds (0.4/2=0.2kcal/mol). A comparison of 1,2-difluoroethane and 1,2-dichloroethane is informative. In other words their rotational barrier would be lower configuration can be determined by finding the difference between the energies Introduction This Letter is concerned with a molecular dynamics (MD) study of the solvent influence on the kinetics of isomerization of 1,2-dichloroethane (DCE). In addition, Similar calculations give the torsional and steric energy Fluorocarbons are 4 to 5 times heavier than air, so it tends to concentrate in low-lying areas. [5], 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. Plot to create the input file. i inversion through a center of symmetry. Both chlorines are electronegative, so pull electrons towards them from the carbon attached to them. the contribution of the eclipse C-H, C-H bonds (1.4-1.0=0.4 kcal/mol), Phys. the fluorine atom. This The most 1,2-difluoroethane Data: For this project, the various conformations of 1,2-difluoroethane were examined. on an adjacent carbon atom. 1,2-Difluoroethane is a saturated hydrofluorocarbon containing an atom of fluorine attached to each of two carbons atoms. 1,1-Difluoroethane is colorless, odorless gas shipped as a liquefied gas under its vapor pressure. Log Octanol-Water Partition Coef (SRC): Log Kow (KOWWIN v1.67 estimate) = 1.11 Boiling Pt, Melting Pt, Vapor Pressure Estimations (MPBPWIN v1.42): Boiling Pt (deg C): -21.66 (Adapted Stein & Brown method) Melting Pt (deg C): -145.53 (Mean or Weighted MP) VP(mm Hg,25 deg C): 3.51E+003 (Mean VP of … NACRES NA.22. Predicted data is generated using the US Environmental Protection Agency’s EPISuite™. rotation about the single bond between the two carbons resulting in an 1. stable conformer, anti, a value of 0 kcal. It can exist as either of two geometric isomers, cis-1,2-dichloroethene or trans-1,2-dichloroethene, but is often used as a mixture of the two.. the substituent groups eclipse each other (figure 1), and second, the staggered That's it! kcal/mol, for the C-H, C-H bond rotation used in my calculations would This was arrived at by finding the repulsion between the fluoro group and the hydrogen and account for In addition, inhaled fluorocarbons causes the myocardium to become more sensitive to catecholamines, which results in deadly cardiac arrhythmias. The C. i. Gauche Effect in 1,2-Difluoroethane. The GAMESS program was used to determine The Australian government classifies 1,2-difluoroethane as an exotic synthetic greenhouse gas. Read more about Gauche Effect. In this compound, there is a fluorine atom attached to each of the carbon atoms. The bond dipoles of C–F and C–Cl are similar, with the latter being slightly larger because of its longer bond. It has a HFC name of HFC-152 with no letter suffix. hydrogen atom somehow reduces this repulsion significantly. CAS Number 75-37-6. it is accurate to conclude that putting the fluorine atom in place of the Literature values for the torsional energy of a C-H bond the optimized energies of the gauche and anti conformers and the saddle There is free This cis C-H bonds and the C-F σ* interactions are significant. [10] Natural bond orbital deletion bond calculations show that 1,2-difluoroethane prefers the gauche conformation due to hyperconjugation effects. Another phenomenon that Fleming touches on which he uses the same explanation for is the preference for the gauche conformation in 1,2-difluoroethane. Program can provide information about their relative stabilities which This point group contains only two symmetry operations: E the identity operation. This would also account for the torsional Two products are formed CH2FCCl2F and CHClFCHClF. Linear Formula CH3CHF2. 1) has been extensively studied and established near 0.8 kcal/mol. This would reduce calculations for fluoroethane, 1,1,2,2-tetrafluoroethane, and perfluoroethane The dihedral angle of about 72° is a result of decreasing hyper conjugative stability and decreasing steric destabilization. Explain why trans-1,2-difluoroethane is a non-polar molecule that while cis-1,2-difluoroethane is a polar molecule. If the fluorine is pulling Another example is 1,2-dimethoxyethane. Acrylonittrile has the formula CH2=CH-CN. As such it may be controlled by government regulation. Its vapors are heavier than air and a flame can travel back to the source of leak very easily. group. [6], Ethylene reacts explosively with fluorine yielding a mixture of 1,2-difluoroethane and vinyl fluoride. Electron density in the molecule is shifted toward above), which is significantly less than the torsional energy to rotate It has a warming equivalent to 140 times that of carbon dioxide. [11], CH2FCH2F reacts with chlorine when treated with light. To start with, the last part of the conclusion caused Could this be enough to restrict rotation? The interaction of substituent groups on two adjacent energy in addition to issues involving steric hindrance. 3-D then transferring their cartesian coordinates to MacMol By convention, of rotation about the C-C bond. that the fluoro group is expected to have more steric strain than hydrogen, Structure, properties, spectra, suppliers and links for: 1,1,2-Trichloro-1,2-difluoroethane, 354-15-4. the energy required for one substituent to rotate past another substituent Due to the arrangement of atoms, rotation about the C-C bond results in me to rethink some of my calculations. While torsional energy is usually very low and that the steric strain from two fluorines on adjacent carbon atoms is less 1,2-Dichloroethene, commonly called 1,2-dichloroethylene or 1,2-DCE, is an organochloride with the molecular formula C 2 H 2 Cl 2.It is a highly flammable, colorless liquid with a sharp, harsh odor. of the anti and gauche conformations, 0.6 kcal/mol. One way is through volatilization from rivers and lakes. The proportions of each depends on the solvent. than the steric strain between two methyl groups. First, because it has a high density, it can displace oxygen in the lungs causing suffocation. is summarized in table 1 below, as well as figure 7, which shows the relationship This leak can be either a liquid or vapor leak. interesting phenomena. The molecule selected for analysis is 1,2-difluoroethane. Synonyms: 1,2-difluoroethane, R152 It is easily ignited. molecular orbital calculations. [15], CH2FCHF + O2 → CH2FCHFO2 peroxy radical, CH2FCHFO2 + NO → CH2FCHFO alkoxy radical, When catalysed by chlorine atoms and oxidised by nitrogen oxides the end product is HCOF which can decompose further to HF and CO.[15], The halflife in air is between 140 and 180 days. In both molecules there are chlorine atoms attached to the alkene. These calculations suggest that most of the solva- tion energy of 1,2-difluoroethane is indeed due to di- polar interactions, as expected. for 1,2-difluoroethane, it appears that the torsional energy for the C-H Using the data above for 1,2-difluoroethane, it appears that the torsional energy for the C-H eclipse with C-F is only 0.2 kcal/mol. GAMESS uses ab initio molecular eclipse with C-F is only 0.2 kcal/mol. and a boiling point of 40° to 150°C. Computational analysis of these conformers using the GAMESS two hydrogens past each other (1.0 kcal/mol). 84, 4205 (1986). [16], Except where otherwise noted, data are given for materials in their, "The role of molecular flexibility in accelerating intramolecular vibrational relaxation", "High Resolution Spectroscopy of 1,2-Difluoroethane in a Molecular Beam: A Case Study of Vibrational Mode-Coupling", https://toxnet.nlm.nih.gov/cgi-bin/sis/search/a?dbs+hsdb:@term+@DOCNO+6786, "Fluoroacetate-Mediated Toxicity of Fluorinated Ethanes", "Ozone Protection and Synthetic Greenhouse Gas Management Amendment Regulations 2004 (No 1)", https://en.wikipedia.org/w/index.php?title=1,2-Difluoroethane&oldid=1017793157, Pages using collapsible list with both background and text-align in titlestyle, Articles containing unverified chemical infoboxes, Creative Commons Attribution-ShareAlike License, This page was last edited on 14 April 2021, at 16:43. 3. This is the famous example of why 1,2-difluoroethane adopts a gauche rather than antiperiplanar conformation. totally eclipsed (figure 3) occurs when the two fluoro groups are eclipse. Anti (figure 6) refers to the conformer with the two fluoro groups staggered I'm done. Contact with the liquid can cause frostbite. The output energies from GAMESS two staggered conformations and two eclipse conformations. and capable of forming an azeotrope with at least one of said 1,1,2,2-tetrachioro-1,2-difluoroethane and 1,1,2-trichloro-1,2,2-trifluoroethane. of the molecule. A cleaning composition containing 1,1,2,2-tetrachloro-1,2-difluoroethane, 1,1,2-trichloro-1,2,2-trifluoroethane and at least one other organic solvent having a melting point of not more than 15°C. Here I offer another spin-off from writing a lecture course on conformational analysis. Gauche (figure 5) refers to a 60 degree rotation from totally eclipse. The torsional and steric energies of the eclipse C-F, C-F bonds in the These fluorine atoms cause an additional strain in the molecule. eclipsed with another C-H bond is 1.0 kcal/mol. considering steric strain is related to size of the electron clouds which the fluorine atoms and away from the hydrogen atoms. 1,2-Difluoroethane is likely to be similarly toxic to humans. First of all torsional energy is basically remaining steric energy in the gauche conformer is only 0.6 kcal/mol. [12] [4] In the liquid form these are about equally abundant and easily interconvert. Data for both molecules the steric energy remaining between the two fluoro groups in the gauche This increases the risk of inhalation. [13], When inhaled by rats, 1,2-difluoroethane is converted to fluoroacetate using cytochrome P450 and then to fluorocitrate both toxic. This effect is present in 1,2-difluoroethane (H 2 FCCFH 2) for which the gauche conformation is more stable by 2.4 to 3.4 kJ/mole in the gas phase. Using the data above The input files for GAMESS were created by first constructing the With solid fluorine it will react when triggered by near-infrared radiation. When cooled to cryogenic temperatures it can have different conformers, gauche and trans. orbital calculations to create an output file with the desired information. 2. (1,1,1,2-tetrafluoroethan was next but my wife turned off the computer Synonym: HFC-152a. [7], If a C-H bond is over excited with too much vibration, the intramolecular vibrational relaxation takes 490 picoseconds. 1,2‐Difluoroethane. A simple example for a C i symmetric molecule is 1,2-dichloro-1,2-difluoroethane (C 2 H 2 Cl 2 F 2) in its staggered conformation displaying an anti -conformation of chloro and fluoro substituents. the difference between the eclipse and the anti (1.4-0=1.4), subtracting Based on the comparison with butane, it can be inferred In trying to understand the interactions, I did ab initio 1,2-difluoroethane is toxic to humans through several mechanisms. was determined by finding the difference between the anti and totally eclipse The Journal of Physical Chemistry A 2005 , 109 (6) , 1223-1229. As a gas it is mostly the gauche form. conformer, in which one carbon is rotated 60 degrees from the eclipse position The two forms which reveal the the remaining steric energy in the gauche conformer is determined to be Jump to main content Jump to site nav. [3], 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%. (1 Hartree = 627.5 kcal) and the energies were rescaled to give the most two pairs of eclipse C-H bonds (5.1-2*1.0=3.1kcal/mol). When cooled to cryogenic temperatures it can have different conformers, gauche and trans. For the best answers, search on this site https://shorturl.im/EGppG. of the totally eclipse conformer in butane, 3 kcal/mol. In the trans molecule, the dipole to one chlorine with relation to the centre of the molecule, is balanced out by the chlorine on the opposite corner of the molecule. of torsional strain. Draw a line bond formla for acrylonitrile and label sigma bonds, pi bonds, which carbon atoms are sp2 hybridized and which carbon are sp hybridized. point for the two eclipse conformers. Acta 37A, 285 (1981). H. Gunthard, Spectrochim. [9], The F-C-C-F dihedral angle is about 72°. The cis one is polar. Reading ModeHere I offer another spin-off from writing a lecture course on conformational analysis. These units were converted to kilocalories Hyperconjugation, Bent Bonds, Steric Repulsion. If the molecule is a dipole, the substance is polar. 1,2-Difluoroethane is a saturated hydrofluorocarbon containing an atom of fluorine attached to each of two carbons atoms. The 1,1,2,2-tetrafluoroethane gave results How to detect Difluoroethane, 1,2-Formula: C2H4F2 | CAS: 624-72-6. between the relative potential energies of the conformers and the angle This is as expected are smaller for fluorine. It's a difference in Electronegativity inside the molecule. IUPAC Standard InChIKey: AHFMSNDOYCFEPH-UHFFFAOYSA-N CAS Registry Number: 624-72-6 Chemical structure: This structure is also available as a 2d Mol file; Other names: Ethylene difluolride; CH2FCH2F; Ethane, 1,2-difluoro-; FC143; Fluorocarbon fc143; Freon 152 Permanent link for this species. MDL number MFCD00000449. You have to think what the reason for polarity or non polarity, in this case, is. 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. Here it is degraded by reaction with hydroxyl radicals and oxygen. totally eclipse conformer was calculated to be 3.1 kcal/mol. Steric strain is assumed to be a component Provide specific examples of the following: A. This colorless gas is used as a refrigerant, where it is often listed as R-152a (refrigerant-152a) or HFC-152a (hydrofluorocarbon-152a). This implies that di- electric friction could be a major contributor to the friction on the torsional coordinate. (figure 2). The torsional energy on the other hand is a mush more does not hinder rotation under normal conditions, it is interesting to of the totally eclipse conformer are approximately the same, however, the In comparing the 1,2-difluoroethane with ethane, the torsional energy for High-resolution infrared spectra have been recorded for three isotopomers, the 13C2, d2, and d1 species. The same explanation can be used for 1,2-dichloroethene. Point Group. Explain why trans -1,2 difluoroethane is a non-polar (has a net zero dipole moment) molecule while cis-1-2- difluoroethane is a polar molecule. 100 parts per million in the atmosphere was sufficient to poison rats in 30 minutes and to kill them in four hours. Hyperconjugation, Bent Bonds, Steric Repulsion. electron density away from the hydrogens, then the torsional energy, 1.0 were in units of Hartrees. P. Huber-Walchli and Hs. They have modest solubility in the reduced torsional strain. 0.9 kcal/mol. 1. similar to the difluorethane, but the perfluoroethane (only 1 staggered If released to air, a vapor pressure of 616 mm Hg at 25 °C indicates 1,2-difluoroethane will exist solely as a vapor in the atmosphere. torsional strain is a result of the repulsion of the electron clouds, then conformers in Chem singly bonded carbon atoms can be examined by determination of the torsional 1,2-Difluoroethane's former production and use as a refrigerant may have resulted in its release to the environment through various waste streams. Considering the fact This creates a dipole. and told me to go to bed). how do we explain the low torsional energy? [14], 1,2-Difluoroethane can enter the environment various ways. It is an isomer of 1,1-difluoroethane. and 1 eclipse conformer), had a rotational energy barrier of 46.4 kcal/mol. Since F is much more electronegative than the C atom, it will have greater electron density for the bonding orbital (Carbon-fluorine bond). The formula can be written CH2FCH2F. conformers (5.1-0=5.1kcal/mol) and subtracting the contribution of the examine the rather low value for the C-F bond rotating past a C-H bond. EC Number 200-866-1. It is also explained in the same paragraph on p. 89. The existence of competing electrostatic interactions between the fluorine and the substituents at C-2 was indicated by the detailed geometries of the gauche conformers and by the calculated sensitivity of the gauche–anti energy differences to the presence of a polar solvent. 180 degrees apart. infinite number of conformational isomers. Project - Rotational barrier in 1,2-Difluoroethane calculated by ab initio thorsley@pennington.org. For comparison to the structure of the cis isomer with its puzzlingly lower energy, the complete structure of trans-1,2-difluoroethylene, a nonpolar molecule, has been determined. It is also used as a propellant for aerosol sprays and in gas duster pr obvious answer simply takes into account the high electronegativity of This is the famous example of why 1,2-difluoroethane adopts a gauche rather than antiperiplanar conformation.

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