2E.2 Determing strongest dipole moment between resonance structures

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Charlene Datu 2E
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Joined: Wed Sep 11, 2019 12:16 am

2E.2 Determing strongest dipole moment between resonance structures

Postby Charlene Datu 2E » Sat Nov 16, 2019 4:01 pm

I don't know how to add a picture into posts, or if it's even possible so here is the problem description.

2E.29 There are three isomers of dichlorobenzene, C6H4Cl2, which differ in the relative positions of the chlorine atoms on the benzene ring. (a) Which of the three forms are polar? (b) Which has the largest dipole moment?

Description of structures:
1) 6-carbon ring with 2 Chlorine atoms attached to 2 directly adjacent carbons (top and top right)
2) 6-carbon ring with 2 chlorine atoms asymmetrically attached to 2 carbons (top and bottom right)
3) 6-carbon ring with 2 chlorine atoms symetrically positioned on the top and bottom carbons

I understand how to do part a, but I don't understand how to relate the structure to which has the strongest dipole moment. Would the more polar or more nonpolar molecule have a larger dipole moment?

Siddiq 1E
Posts: 106
Joined: Fri Aug 09, 2019 12:15 am

Re: 2E.2 Determing strongest dipole moment between resonance structures

Postby Siddiq 1E » Sat Nov 16, 2019 4:05 pm

I don't know if it necessarily has to do with which is more or less polar, but I think it has to do with the direction and cancellation of dipoles. There will be a stronger dipole moment in the structure where dipoles are in the same direction.

Aadil Rehan 1D
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Joined: Thu Jul 11, 2019 12:16 am
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Re: 2E.2 Determing strongest dipole moment between resonance structures

Postby Aadil Rehan 1D » Sat Nov 16, 2019 4:29 pm

The more polar a molecule, the stronger the dipole moment. Dipoles moments arise from regions of high electron density, and when the chlorine atoms are close to each other, the electron density is higher. Thus, I believe that the 6-carbon ring with 2 Chlorine atoms attached to 2 directly adjacent carbons (or o-dichlorobenzene) has the strongest dipole moment of them.


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