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Consider a covalent molecule such as carbon tetrafluoride. In $\ce{CF4}$, each $\ce{C-F}$ bond is polar covalent. However, this substance is considered overall non-polar because each bond dipole moment cancels out each other, resulting in a negligible molecular dipole moment. This explains why it is non-polar. But how can that be the case? Certainly, such a substance with such strong bond dipoles would have some sort of strong interaction with polar solvents? Why do we not take the individual bond dipole moments into consideration?

Tan Yong Boon
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    Related: Why is carbon dioxide nonpolar?; What are dipole moments in a molecule supposed to act upon? – orthocresol Sep 24 '17 at 10:05
  • @orthocresol Just to clarify, I completely understand why CF4 is nonpolar. What I don't understand is why the polar C-F bonds don't seem to affect it's interactions with polar solvents. – Tan Yong Boon Sep 24 '17 at 11:42
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    I'm voting to close this question as off-topic because it's based on false premise. – Mithoron Sep 24 '17 at 13:19
  • @Mithoron May I know what is that false premise? – Tan Yong Boon Sep 24 '17 at 14:00
  • @TanYongBoon Dipole moment is a vector, so it's all about the vector sum. Just as a satellite on a stationary orbit appears to be stationary for the observers on Earth, when centrifugal force and gravitational force equalize each other, same happens with four polar $\ce{C-F}$ bonds. – andselisk Sep 24 '17 at 15:01
  • Basic idea of your question? Short answer to question in title is "It isn't". – Mithoron Sep 24 '17 at 15:21
  • I kinda get your question, and it's a good one. Basically, even though carbon dioxide is non-polar, it dissolves in water. And how is that? Basically the relatively positive carbon atom attracts the negative end of the water dipole, and the two negative oxygens attract the positive end of the dipole. But why isn't this the case for $\ce{CF4}$ is your question right? – Pritt says Reinstate Monica Sep 24 '17 at 16:10
  • @andselisk I already understand this concept. What I'm interested in is why inidividual bond dipoles do not contribute to the interactions of an overall nonpolar solute molecule with polar solvent molecules. – Tan Yong Boon Sep 24 '17 at 22:53
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    @PrittBalagopal You can actually extend my question to all nonpolar covalent molecules with polar individual bond dipole moments. It is not restricted to CF4 or CO2. – Tan Yong Boon Sep 24 '17 at 22:54
  • See discussion here: https://chemistry.stackexchange.com/questions/41952/is-the-triiodide-ion-polar – Mithoron Sep 24 '17 at 23:08
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    @Mithoron Thanks for sharing the insightful link. However, I don't think it answers my question – Tan Yong Boon Sep 25 '17 at 14:56
  • "inidividual bond dipoles do not contribute to the interactions of an overall nonpolar solute molecule with polar solvent molecules" They do! – Mithoron Sep 25 '17 at 15:36
  • @Mithoron Ok I get what u mean. An example would be the water-soluble carbohydrates with many polar hydroxyl groups. However, I am saying that the main determinant is still the molecular dipole. Not individual bond dipoles. For example, could u explain the interact of CF4 and CH4 in water. This is an example of my case. Because the C-F bond is hugely polar but the C-H bond isn't that polarised. How would this affect their solvations in water. Are you clearer now? – Tan Yong Boon Sep 25 '17 at 22:43
  • https://chemistry.stackexchange.com/questions/7147/why-distinguish-between-polarity-and-hydrophobicity https://chemistry.stackexchange.com/a/645/9961 and here is your duplicate: https://chemistry.stackexchange.com/questions/80695/why-are-fluoroalkyl-chains-hydrophobic-oleophobic – Mithoron Sep 25 '17 at 23:20

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