I've looked at and drawn the structure, and I originally felt that it would be nonpolar - as I believe all the dipoles would cancel out, but I'm not 100% sure. I might be too dependent on the fact that it looks symmetric.

Also, is it true that the overall molecule shape would be planar? And is the hybridization of the oxygen atoms sp3 like I think they are?

Edit: Thanks to a commenter, I have changed the question to ask about the dipole moment in hopes of being more clear. I'd also like to add that this is a homework question that I am stuck on (for general chemistry l) and the teacher hasn't been the most thorough which is why I am here trying to teach myself.

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  • $\begingroup$ Because of the molecule symmetry its dipolar moment is null and you're right about oxygen hybridization. The two planes perpendicular to the molecule allows you to conclude that there is no net dipolar moment in there... $\endgroup$
    – user43021
    Apr 5 '18 at 21:49
  • $\begingroup$ Polarity is a property of solvent, equalling polarity with dipole moment is tragic misapplication of concept. $\endgroup$
    – Mithoron
    Apr 5 '18 at 22:10
  • $\begingroup$ I mean, I didn't come up with the question and that's one of the ways which is taught to figure out molecular polarity, hence coming here to ask for help... $\endgroup$
    – summer
    Apr 5 '18 at 22:24
  • $\begingroup$ I think loosely using polar/nonpolar to describe a molecule qualitatively is ok and people do it on a daily basis, but it can be ambiguous/debatable, see for example the discussion here. In this case I think it is perfectly clear from context what you mean, but a more precise wording (that leaves no room for nitpicking) would be something like "Does xyz molecule have a nonzero dipole moment?" $\endgroup$
    – orthocresol
    Apr 5 '18 at 22:41
  • $\begingroup$ Here is another example of problems it causes chemistry.stackexchange.com/questions/65188/… $\endgroup$
    – Mithoron
    Apr 5 '18 at 23:11

The best answer for this seems to be in Structure, Energy, Vibrational Frequencies, and Potential Energy Curve of 2,3,7,8-Tetrachlorinated Dibenzo-p-dioxin: Ab Initio MO Studies J. Phys. Chem., 1996, 100 (12), pp 4810–4814.

This research finds that though planar is the lowest energy conformation, the energy for bending with respect to the O-O axis from 180 degrees to 170 degrees is only 0.008 kcal/mol. The molecule flaps like a butterfly.

The article says:

At ambient temperatures, nonplanar conformations will be significantly populated for this potential. This prediction accounts for the experimental results that the electric dipole moment of the DD molecules is reported to be 0.64 D. [reference 24]

Where "DD" means the unsubstituted dioxin and where reference 24 is Higashi, K.; Uyeo, S. J. Chem. Soc. Jpn. 1941, 62, 396.


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