trans/cis

(Polar molecules, Non-polar molecules, etc.)

Moderators: Chem_Mod, Chem_Admin

hannahdaijo_4H
Posts: 48
Joined: Fri Sep 28, 2018 12:27 am

trans/cis

Postby hannahdaijo_4H » Thu Nov 29, 2018 4:06 pm

Could someone help explain trans/cis molecules and what dictates which structure a molecule is? The book (7th edition) uses dichloroethene (C2H2Cl2) as an example of trans and cis molecules.

Albert_Luu3K
Posts: 62
Joined: Fri Sep 28, 2018 12:23 am

Re: trans/cis

Postby Albert_Luu3K » Thu Nov 29, 2018 4:44 pm

Hello,

The way I imagine trans/cis molecules is that there are two different lewis structures that the molecule would be. To differentiate, which lewis structure is correct and what the molecule they are asking for is, trans or cis is added to the front. Cis molecules like cis-dichloroethene are polar because the dipoles on either side do no cancel each other out. In cis molecules and in cis-dichloroethene for example, the Cl are on the same side of either C atom. Both sides would have dipoles pulling towards the Cl, so they do not cancel. In the trans-dichloroethene, the Cl are on opposite sides attached to their C atom, so even though both have high electronegaticity, they are on opposite sides which cancel each other out. Trans molecules would not be polar. Hope this kinda helps! Google is also a nice tool

hannahdaijo_4H
Posts: 48
Joined: Fri Sep 28, 2018 12:27 am

Re: trans/cis

Postby hannahdaijo_4H » Thu Nov 29, 2018 5:56 pm

So the only way to identify whether a molecule is trans or cis is by the molecule's systematic name rather than merely by the molecular formula?

Carlos De La Torre 2L
Posts: 60
Joined: Tue Oct 09, 2018 12:16 am

Re: trans/cis

Postby Carlos De La Torre 2L » Thu Nov 29, 2018 10:52 pm

yes because the formula for a cis/trans molecule is the exact same, the difference comes in how the atoms are positions which is where the cis/trans part comes in it tells you is the same elements are on the same side or on the opposite side

Elle_Mendelson_2K
Posts: 72
Joined: Fri Sep 28, 2018 12:28 am

Re: trans/cis

Postby Elle_Mendelson_2K » Thu Nov 29, 2018 11:35 pm

another thing to note is that cis and trans usually are isomers meaning they have different properties. For example, one isomer can be polar while another can be non polar.


Return to “Determining Molecular Shape (VSEPR)”

Who is online

Users browsing this forum: No registered users and 3 guests