1, 2-Dichloroethylene, cis

Dichloroethylene cis-1,2-Dichloroethylene trans-1,2-Dichloroethylene Dichlorofluoromethane (Freon 21) Dichloromethane... 

However when bulkier phenyl groups are present as in 1,2 diphenyl ethylene (also called stilbene) the equilibrium mixture at room temperature contains several thousand times the trans form as compared to the cis. This is because of the energy difference between the two. But these empirical generalizations hold good only when the groups in question are alkyl radicals. For example the cis 1,2 dichloroethylene is more stable than trans. This is not very well understood at present. 

UV data shown in Table 26 clearly support our expectations. For example, the mr transition energy for cis 1,2-dichloroethylene is 42300 cm-1 while the same quantity is 41700 cm-1 in the corresponding trans molecule. The same trend is observed in the 1,2-difluoroethylenes, as well as in the 1,2-dialkylethylenes, where a distinct hypsochromic shift is observed in the comparison of trans and cis isomers. 

Investigation of the concentration dependence of/13 of trichloroethylene and cis 1,2-dichloroethylene (Table 8) over the range of 50-100 mole % showed a small but significant change. Both cis and trans isomers of the dichloro and dibromoethylenes show the same slopes for the concentration dependence (Figs. 1 and 2). This is inconsistent with the idea of a reaction field effect since... 

Phenylthioacetylene has been prepared by elimination of thiophenol and dehydrobromination of cis-1,2-bis(phenylthio)ethylene5 and cis-1-bromo-2-phenylthioethylene,2 7 respectively. The latter was obtained by addition of thiophenol to propiolic acid in ethanol and subsequent one-pot bromine addition, decarboxylative dehalogenation, and careful distillation to remove the trans isomer.2.7 on the other hand, cis-1,2-bis(phenylthio)ethylene was prepared by double addition of thiophenol to cis-1,2-dichloroethylene.5a d Although these procedures can provide useful amounts of phenylthioacetylene, they were found to be somewhat less satisfactory in our hands as far as operation and/or overall yields are concerned. Furthermore, we have encountered problems with regard to the reproducibility of one-pot dehydrobrominations of phenylthio-1,2-dibromoethane.6 However, the stepwise execution of the double dehydrobromination, as described in the modified procedure reported here, provides preparatively useful quantities of phenylthioacetylene in a practical manner. 

OICHLOROETHYLENE cis-1,2-DICHLOROETHYLENE trans-1,2-DICHLOROETHYLENE CHLOROACETYL CHLORIDE... 

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