H-F H-F Hydrogen Bonding vs Dipole-Dipole

[Sunny Wu 3A]

In Lecture 17, Dr. Lavelle listed H-F H-F as an example of a dipole dipole interaction with an approx. energy of -2 kJ/mol:



However, wouldn't this attraction be more specifically classified as hydrogen bonding, and so wouldn't the energy be approx. -20 kJ/mol?

[Adrienne Chan 1G]

Not an answer per se, but I had the exact same question. Fluorine is even more electronegative than oxygen, so I thought, if anything, the hydrogen bonding between HF molecules would be stronger. Curious to see if anyone understands Lavelle's thought process!

[Ke Huang 2G]

I think both hydrogen bonding and dipole-dipole forces are involved. The -2kj/mole might only represent the dipole-dipole force.

[Laura 3l]

I believe since this is a dipole dipole force then it would also be a Hydrogen bond.

[Darren1j]

I had this same question and I think there's a reason for that difference. In this case H-F H-F, I think its classified as a hydrogen bond and therefore would be -20 but other dipole-dipole interactions that are not hydrogen bonding would be around -2. H Bond is Dipole-Dipole, but dipole- dipole doesn't have to be h-bond.

[Charlotte Adams 1A]

I am also confused because we in the HW we were shown an H-F bonding to another H-F and it said the intermolecular force shown was hydrogen bonding.

[Joanna Huang]

I believe both Hydrogen bonding and Dipole-Dipole forces are at work! Since one molecule is strongly polar (F), the polar ends of the molecule will attract the hydrogen. Because hydrogen only needs one pair of electrons, it can also form a hydrogen bond with F, which is strongly electronegative.

[Shrinidhy Srinivas 3L]

You're right when you say that hydrogen bonding is involved here. However, I believe that Dr. Lavelle was just referring to the fact that H-F has both dipole-dipole interactions and hydrogen bonding. Both have separate energies. Hope this helps!

[Izamary Marquez 2H]

In addition, when calculated a dipole moment, will |q| always be given?

[ShinwooKim_3E]

H-F has both hydrogen bonds and dipole-dipole bonding!

[Xavier Herrera 3H]

The bond between the H and the F would be both a dipole-dipole bond and a hydrogen bond, since hydrogen bonds are basically stronger versions of regular dipole-dipole bonds. So, I would think that this attraction should be -20kj/mol, rather than -2kj/mol.

[Charlotte Adams 1A]

In addition, when calculated a dipole moment, will |q| always be given?

I don't think we will have to calculate the dipole for the test.