I'm pretty sure these molecules are polar

[aclark609]

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?

 

[DrClaude]

All these molecules are polar. It's hard for me to see how dipole-dipole interactions would be negligible compared to dispersion forces.

 

[aclark609]

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.

 

[chemisttree]

There isn't.

 

[janhaa]

for example chloromethane is non-polar because it's a symmetrical molecule and its dipole moments cancel each other out...

 

[DrClaude]

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.

 

[DrClaude]

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.