Polarity of CH2Cl2

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

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Louise Zhuang
Posts: 31
Joined: Fri Sep 28, 2018 12:28 am

Polarity of CH2Cl2

Postby Louise Zhuang » Wed Nov 28, 2018 11:24 pm

In 6th edition question 4.25, the answer key suggest that CH2Cl2 is polar. But if we draw the lewis structure in which the two Cl atoms are opposite to each other, wouldn't the charge cancel out and make the molecule nonpolar? How do we know which way to draw?

Kaylee Kang 1G
Posts: 65
Joined: Fri Sep 28, 2018 12:24 am

Re: Polarity of CH2Cl2

Postby Kaylee Kang 1G » Wed Nov 28, 2018 11:57 pm

This is because CH2Cl2 is tetrahedral, so it doesn't actually cancel out perfectly like it appears to with its Lewis structure.

Patrick Cai 1L
Posts: 93
Joined: Fri Sep 28, 2018 12:25 am

Re: Polarity of CH2Cl2

Postby Patrick Cai 1L » Wed Nov 28, 2018 11:58 pm

This Lewis structure does not reflect the 3D structure of CH2Cl2, which is tetrahedral. With this arrangement, no matter what, at least two corners of the tetrahedron has chlorine atoms. This, along with the difference in electronegativity of chlorine and carbon, produces a net nonzero dipole moment and thus a polar molecule.

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