How to Differentiate between Cis and Trans

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Uma Ramaratnam 2I
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Joined: Fri Sep 25, 2015 3:00 am

How to Differentiate between Cis and Trans

Postby Uma Ramaratnam 2I » Sun Feb 28, 2016 9:29 pm

How do you draw a cis and trans molecule with the same atoms, like what is the geometric difference?

504650118
Posts: 11
Joined: Fri Sep 25, 2015 3:00 am

Re: How to Differentiate between Cis and Trans

Postby 504650118 » Sun Feb 28, 2016 11:50 pm

The cis prefix means the atoms are on same side. For example, in dichloroethene, you can have the two chlorine atoms both on the same side or on the opposite sides. If you decide to draw this out and put chlorine on opposite sides, you would have a trans-1,2-dichloroethene, with the chlorine atoms across from eachother.

*Note that for something like 1,2-dichloroethane, it doesn't have geometric isomers. This is because the single C-C bond allows the chlorine atoms to rotate in the bond. On the other hand, dichloroethene does have geometric isomers because the double bond between the carbons restrict the chlorine atoms from rotating.


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