Dipole moments and resonances

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Dipole moments and resonances

Postby rkang00 » Sat Dec 01, 2018 7:57 pm

If a molecule's dipole moments cancel out, does this mean that structures with resonance have no net dipole movement? I think that was the case for neutral sulfite (SO3); it has resonance but the real molecule in reality has the bond length equal to the average of the bond lengths of the resonance structures, and the dipole moments cancel each other.

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Re: Dipole moments and resonances

Postby amogha_koka3I » Sat Dec 01, 2018 10:03 pm

I think the patterns for such molecules would follow that of SO3, but I would search for exceptions just in case so you don't make generalizations.

Emily Li 4A
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Re: Dipole moments and resonances

Postby Emily Li 4A » Sat Dec 01, 2018 10:08 pm

Is there a source where we can find all of the exceptions in one place?

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Re: Dipole moments and resonances

Postby MinaChoi_3H » Sat Dec 01, 2018 11:11 pm

If a molecule does have dipole moments I'm not sure resonance would necessarily cancel out the dipole moments. This is because a molecule's dipole moments are due to the electrons being closer to one atom than the other in one specific bond of the molecule. Resonance distributes the electron density throughout the entire molecule, but that does not mean that electrons are shared equally between two atoms that have a high difference in electronegativity. So resonance would distribute the electron density evenly between let's say all the O-H bonds in a molecule, but within the O-H bonds, electrons are more closely gathered to oxygen which still creates a dipole moment (if the symmetry of the molecule does not cancel out the polarities).

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