Trans-1,2-difluoroethylene

CIS- And trans-1,2-difluoroethylene are oxidized by ozone stereoselectively to a mixture of the corresponding epoxides and ozonides with formyl fluoride The composition of the mixture depends on the solvent used [25] (equation 16)... 

Fig. 11. The orbital pattern of sigma fluorine lone pair AO s and sigma C = C MO s in cis and trans 1,2 difluoroethylene. Orbitals q the same symmetry interact...

Another reliable index is the sum of the overlap populations of AO pairs spanned by the MO s the interaction of which we focus upon. For example, consider the nA—n interaction in cis and trans 1,2-difluoroethylene (Fig. 7) and its consequences. 

The interaction diagram for the cis and trans union of two FHC radical fragments is shown in Fig. 38. From Fig. 38 it is obvious that the pi HOMO-LUMO splitting is larger for the case of cis union than for trans union. The final conclusions is that the HOMO and LUMO energies in cis and trans 1,2-difluoroethylene vary in the following way ... 

We now consider the effect of nonbonded interaction on the energies of pi lone pair MO s in cis and trans disubstituted ethylenes. Our model systems are again cis and trans 1,2-difluoroethylene. The consequence of the interaction of the pi lone pair electrons in the cis and trans geometries is shown in Fig. 36. We distinguish the following three hypothetical cases and work out their consequences. 

Ihrig and Smith 62> report similar changes for 3J % of cis-1,2-difluoroethyl-ene and of trans-1,2-difluoroethylene (Table 23). The cis coupling changes... 

From the molecular formulas, these spectra must arise from cis and trans 1,2-difluoroethylene.The spectrum of the third isomer, 1,1-difluoroeth-ylene, was shown in Fig. 6.1 and is analyzed in Appendix B. 

Attachment of thermal electrons to perfluoro-cyclopentene and -cyclohexene has been studied. The rates of proton transfer from CHs+ and H3+ to cis- and trans-1,2-difluoroethylene have been measured in a study of gas-phase ion-dipole inter-actions.42 In the reaction of the base CDsO" with fluoroethanes in the gas phase, proton transfer and HF elimination, e.g.. Scheme 2, occur at comparable rates, except for the ethane CFs CHa, where elimination predominates and for CF3 -CFaH, where proton transfer occurs exclusively. ... 

Use a molecular-mechanics program to find the geometries and the energy difference between (a) cis and trans 1,2-difluoroethylene (b) cis and trans 1,2-dichloroethylene (c) cis and trans 1,2-diiodoethylene. Compare your results with available literature data as to which is the more stable isomer of eeich peiir. 

Craig, N. C., and Overend, J. (1969). Vibrational Assignments and Potential Constants for Cis- and trans-1,2-Difluoroethylenes and Their Deuterated Modifications. The Journal of Chemical Physics, 51(3) 1127-42. 

Figure 2. The key sigma bonding difference between cis and trans 1,2 difluoroethylene.

Calculations place G substantially below C, with the latter being more stable than trans-1,2-difluoroethylene for reasons discussed before. Both G and C isomers have an identical C core. However, if we separate the ligands into two sets, one containing the two F s and the other containing the two H s, we can see that the G and C isomers differ in one important way In the former, the F and H sets are segregated, i.e., there is only vicinal overlap of F and H AO s, while in the latter case, the two sets are brought into proximity, i.e., there is now appreciable geminal overlap of F and H AO s as they are both attached on the same carbon atom. 

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