Why is CH2Cl2 polar?

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

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Ananta3G
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Why is CH2Cl2 polar?

Postby Ananta3G » Tue Nov 19, 2019 8:48 pm

In question 2.25 in the textbook, it says CH2Cl2 Is polar - why? In the answers, it shows the lewis structure diagram with the Hs next to each other and the Cls next to each other which would cause an uneven distribution of charge so it makes sense that it would be polar, but how would I know to arrange them like that vs opposite each other? Thanks!

alicechien_4F
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Re: Why is CH2Cl2 polar?

Postby alicechien_4F » Tue Nov 19, 2019 8:53 pm

The Cl atom has a much higher electronegativity than H and has more electrons in its valence shell (8 vs. 2) after bonding, so there will be a stronger negative charge on that end of the atom. Hope this helps!

EmilyJoo_1G
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Re: Why is CH2Cl2 polar?

Postby EmilyJoo_1G » Wed Nov 20, 2019 11:23 am

It's polar because Cl has a delta negative charge due to its negativity, which means it would cause a temporary polarization of electrons of atoms around it.

LNgo 1G
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Re: Why is CH2Cl2 polar?

Postby LNgo 1G » Wed Nov 20, 2019 11:27 am

I think the electron repulsion plays a part in orienting the molecule so that the chlorine atoms are not on opposite poles as you might expect, but they are placed next to each other in the molecular structure.

Indy Bui 1l
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Re: Why is CH2Cl2 polar?

Postby Indy Bui 1l » Wed Nov 20, 2019 11:33 am

You should think of this molecule in the 3d form. In a tetrahedral, no matter where you put the atoms the Chlorine atoms will always be next to each other. I can't Draw a picture on here, but just look one up it might be helpful. The lewis structure looks like u can orient the chlorines to be opposite of each other, but in actuality they will always be next to each other in the 3d plane, no matter how u orient them.

KBELTRAMI_1E
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Re: Why is CH2Cl2 polar?

Postby KBELTRAMI_1E » Wed Nov 20, 2019 12:21 pm

Hung Indy Bui 3H wrote:You should think of this molecule in the 3d form. In a tetrahedral, no matter where you put the atoms the Chlorine atoms will always be next to each other. I can't Draw a picture on here, but just look one up it might be helpful. The lewis structure looks like u can orient the chlorines to be opposite of each other, but in actuality they will always be next to each other in the 3d plane, no matter how u orient them.


how do we know they are next to each other?

Rory Simpson 2F
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Re: Why is CH2Cl2 polar?

Postby Rory Simpson 2F » Wed Nov 20, 2019 1:29 pm

KBELTRAMI_4I wrote:
Hung Indy Bui 3H wrote:You should think of this molecule in the 3d form. In a tetrahedral, no matter where you put the atoms the Chlorine atoms will always be next to each other. I can't Draw a picture on here, but just look one up it might be helpful. The lewis structure looks like u can orient the chlorines to be opposite of each other, but in actuality they will always be next to each other in the 3d plane, no matter how u orient them.


how do we know they are next to each other?


If you look at the VSEPR molecular structure, the molecule is tetrahedral. Every atom bound to the central atom is next to each other because of the positions of atoms in that arrangement.

Eva Zhao 4I
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Re: Why is CH2Cl2 polar?

Postby Eva Zhao 4I » Fri Nov 22, 2019 12:27 pm

To add on, typically speaking, a molecule with a tetrahedral shape is only nonpolar if all four atoms bonded to the central atom are the same.

Justin Quan 4I
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Re: Why is CH2Cl2 polar?

Postby Justin Quan 4I » Fri Nov 22, 2019 12:31 pm

Eva Zhao 3B wrote:To add on, typically speaking, a molecule with a tetrahedral shape is only nonpolar if all four atoms bonded to the central atom are the same.

This is because different atoms have different electronegativity. Thus, each atom surrounding the central atom will have a slightly different attraction to the electrons, which will produce a net dipole dipole force.

ranqiao1e
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Re: Why is CH2Cl2 polar?

Postby ranqiao1e » Fri Nov 22, 2019 10:21 pm

Because the Cl is much more electronegative than carbon

Bradley Whitworth 4B
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Re: Why is CH2Cl2 polar?

Postby Bradley Whitworth 4B » Sun Nov 24, 2019 1:02 am

When you add all the dipole moments taking into account shape you get a overall dipole moment so it is polar.

erica thompson 4I
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Re: Why is CH2Cl2 polar?

Postby erica thompson 4I » Sun Nov 24, 2019 10:43 am

I always find it's easier to think about it visually! I would recommend drawing the Lewis structures, and more importantly the molecular structures, and drawing arrows toward the molecules with more negative charge. Think about the trajectories of the arrows you're drawing!

Noah Canio 3C
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Re: Why is CH2Cl2 polar?

Postby Noah Canio 3C » Sun Nov 24, 2019 6:40 pm

If you were to consider the molecule as a 3D shape as opposed to a 2D one, then it's possible to see that the chlorine atoms and the hydrogen atoms are not exactly opposite of each other, which a potential lewis structure would suggest. Because these atoms are not on opposite ends, their dipole moments don't cancel each other out, leading to CH2Cl2 to be a polar molecule.


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