Polar Molecules

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

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Michael Du 1E
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Polar Molecules

Postby Michael Du 1E » Sun Nov 17, 2019 11:58 am

If I'm correct, polar dipoles will only cancel if they are on the opposite side of one another right? However, they will not cancel if the dipoles are adjacent to one another?

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Re: Polar Molecules

Postby CMaduno_1L » Sun Nov 17, 2019 12:03 pm

I believe so, this is according to the example he gave during lecture regarding cis-DICHLOROETHENE (polar) v.s. trans-DICHLOROEHTENE (non-polar). The arrangement of the Cl atoms influences the polarity it seems.

Joowon Seo 3A
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Re: Polar Molecules

Postby Joowon Seo 3A » Sun Nov 17, 2019 12:05 pm

I am not sure what you mean but if dipoles are on the same side (or adjacent to each other) will not mean that they will not cancel out. For example BF3 where the shape is a trigonal planar. There are two fluorides on the bottom side of the molecule and one fluoride on the top, yet it is non-polar.

Erik Buetow 1F
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Joined: Fri Aug 30, 2019 12:15 am

Re: Polar Molecules

Postby Erik Buetow 1F » Sun Nov 17, 2019 12:32 pm

That's correct if I understand the question correctly. We talked about trans-molecules and cis-molecules during class and cis isomers are polar because the charges did not cancel. However, in a trans isomer, because the atoms are placed on opposite sides of the molecules, the partial charges cancel and the molecule becomes non polar

Sofia Barker 2C
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Re: Polar Molecules

Postby Sofia Barker 2C » Sun Nov 17, 2019 12:34 pm

If two dipoles are adjacent to each other, then their combined charge makes the molecule polar. If the dipoles of two of the same atoms lie on the same side of a molecule, this molecule is referred to as "cis." However, if the dipoles of two of the same atom are opposite each other in the molecule, then the dipoles cancel out because there is no net dipole moment. The BF3 example that was given in a previous answer proves that the dipoles of each Fluorine cancel out because of the molecule's symmetry. There is no net dipole moment because each Fluorine is equally far apart from each other, as proved by their equal bond angles. The shape of BF3 shows that there is no 'bottom side' or 'top side' because each fluorine is equidistant from the others.

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