I'm pretty sure these molecules are polar

In summary, the conversation is about the presence of dipole-dipole interactions between polar molecules, specifically CHBr3, CH3Br, CH3Cl, and CHCl3. The professor mentioned that the only intermolecular forces present were dispersion forces, but the individual believes that the dipole attractions are not negligible. The conversation also discusses the symmetry and dipole moments of chloromethane and how someone with a PhD may still miss something obvious in this subject.
  • #1
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Are there not dipole-dipole interactions between CHBr3, CH3Br, CH3Cl, and CHCl3? Assume they are all separate pure substances. My professor today said that the only intermolecular forces present were dispersion forces. Are the dipole attractions negligible due to fact they are too weak?
 
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  • #2
All these molecules are polar. It's hard for me to see how dipole-dipole interactions would be negligible compared to dispersion forces.
 
  • #3
That's what I thought. I'll approach her with this next class period. I don't see how someone with a doctorate could miss something so obvious. There must be more to it.
 
  • #4
There isn't.
 
  • #5
for example chloromethane is non-polar because it's a symmetrical molecule and its dipole moments cancel each other out...
 
  • #6
janhaa said:
for example chloromethane is non-polar because it's a symmetrical molecule and its dipole moments cancel each other out...
It has a C3 symmetry axis along the C-Cl bond, but that bond is highly polar. CH3Cl had a dipole moment of 1.9 D.
 
  • #7
aclark609 said:
I don't see how someone with a doctorate could miss something so obvious.

I've heard PhDs say pretty stupid things!

Depending on her particular field, this might be a subject she is less comfortable with.
 

What does it mean when molecules are polar?

When molecules are polar, it means that there is an uneven distribution of charge within the molecule. This results in one end of the molecule having a slightly positive charge and the other end having a slightly negative charge.

What causes molecules to be polar?

The polarity of a molecule is determined by the electronegativity difference between the atoms that make up the molecule. When there is a significant difference in electronegativity, the electrons are not shared equally, resulting in a polar molecule.

How can you determine if a molecule is polar or nonpolar?

The easiest way to determine if a molecule is polar or nonpolar is to look at its molecular geometry. If the molecule has a symmetrical shape, it is most likely nonpolar. However, if the molecule has an asymmetrical shape, it is most likely polar.

What are some examples of polar molecules?

Some common examples of polar molecules include water, ammonia, and hydrogen fluoride. These molecules have uneven distributions of charge due to differences in electronegativity between the atoms that make them up.

Why is the polarity of molecules important in chemistry?

The polarity of molecules is important in chemistry because it affects many chemical properties such as solubility, boiling point, and reactivity. It also plays a crucial role in biological processes, such as the interaction between molecules in cells.

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