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The two compounds are isomers, each being colorless liquids with a sweet odor. 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. They have modest solubility in water.
These trends can be attributed to the fact that the dipoles of the substituents in a cis isomer will add up to give an overall molecular dipole. In a trans isomer, the dipoles of the substituents will cancel out [7] due to being on opposite sides of the molecule. Trans isomers also tend to have lower densities than their cis counterparts ...
In the cis isomer the two polar C−Cl bonds are on the same side of the C=C double bond and the molecular dipole moment is 1.90 D. In the trans isomer, the dipole moment is zero because the two C−Cl bonds are on opposite sides of the C=C and cancel (and the two bond moments for the much less polar C−H bonds also cancel).
The cis isomer has C 2v symmetry and the trans isomer has C 2h symmetry. These isomers can interconvert, but the process is slow enough at low temperature that the two can separated by low-temperature fractionation. [clarification needed] The trans isomer is less thermodynamically stable [2] but can be stored in glass vessels
Dipole moment. 0 D: ... This colorless solid is an important isomer of the bipyridine family. ... with nitrogen atoms in trans position. [4] ...
1,2-Dibromoethylene can be synthesized by halogenation of acetylene (C 2 H 2) with bromine (Br 2). [1] In order to prevent the formation of tetrahalogenated compounds, acetylene is used in excess, with Br 2 as the limiting reagent.
The two isomers are extremely difficult to separate by distillation because of the proximity of their boiling points (~4 °C for cis and ~1 °C for trans [5]). However, separation is unnecessary in most industrial settings, as both isomers behave similarly in most of the desired reactions.
Molecular symmetry is a fundamental concept in chemistry, as it can be used to predict or explain many of a molecule's chemical properties, such as whether or not it has a dipole moment, as well as its allowed spectroscopic transitions. To do this it is necessary to use group theory.