Methanol polarity

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Methanol polarity

Postby Brigita1D » Sat Nov 18, 2017 9:42 am

Can someone please explain to me why methanol, CH4O, is polar? Textbook problem 4.75 states that the molecule is polar but I am unsure why.
Thank you in advance.

Sabrina Dunbar 1I
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Re: Methanol polarity

Postby Sabrina Dunbar 1I » Sat Nov 18, 2017 10:13 am

When you draw out the lewis structure for the molecule, you can see that the dipoles do not cancel out. Unlike CH4 where the bonded atoms are all the same, methanol has three Hs and one OH. Therefore, the dipoles will not cancel because there are differences in their strengths.

Shawn Patel 1I
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Joined: Thu Jul 27, 2017 3:01 am

Re: Methanol polarity

Postby Shawn Patel 1I » Sat Nov 18, 2017 11:53 am

In methanol, the CH3 group is attached to OH. Oxygen is more electronegative than the rest of the molecule, so there is a slight negative charge on the OH end of the molecule, and this leaves a slight positive charge on the CH3 group. Hydrocarbons are always non-polar, so there is nothing to cancel out the dipole on the molecule.

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