Why is CH2Cl2 polar while CH4 is not?

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Claudia Luong 4K
Posts: 59
Joined: Fri Sep 28, 2018 12:25 am

Why is CH2Cl2 polar while CH4 is not?

Postby Claudia Luong 4K » Sat Dec 08, 2018 4:21 am

I keep reading that the reason why CH2Cl2 is polar because due to its tetrahedral shape, the dipoles can not cancel each other out but doesn't CH4 also have tetrahedral shape too? I assumed, since the reason for CH2Cl2 being polar is apparently due to the 109.5 degree angles from the tetrahedral shape, that this means that the surrounding atoms in all tetrahedral-shaped compounds are not placed directly opposite of each other and that is why the dipoles can't cancel each other out. Am I understanding this wrong? Or if this is the case, then shouldn't the dipoles of the H atoms in CH4 not be able to cancel each other out either because they aren't directly opposite of each other? Is it different because all the surrounding atoms in this case would have the same dipole?

Margaret Akey
Posts: 80
Joined: Fri Sep 28, 2018 12:18 am

Re: Why is CH2Cl2 polar while CH4 is not?

Postby Margaret Akey » Sat Dec 08, 2018 8:57 am

CH4 is a C surrounded by all H's, so all of the H's pull the electrons from the carbon the same amount (i.e. nonpolar). In CH2Cl2, the Cl pulls much more on the Carbon's electrons (since it has higher electronegativity) than the Hydrogens, which sets up a dipole moment (i.e. polar).

Karina Koo 2H
Posts: 49
Joined: Fri Sep 28, 2018 12:24 am

Re: Why is CH2Cl2 polar while CH4 is not?

Postby Karina Koo 2H » Sun Dec 09, 2018 10:12 am

Its because Cl is more electroneg than C and in CH4, everything is shared pretty evenly

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